Blandine Quelennec

Zhibo Duan

Romain Delannoy

Nicolas Gay

Matthieu Briffaut

Vincent Tognetti

Nicolas Delpouve

Laurent Delbreilh

Emmanuel Richaud
email: emmanuel.richaud@ensam.eu

EFFECT OF PHYSICAL AND CHEMICAL AGEING ON BARRIER PROPERTIES OF EPOXY COATING

Keywords: Epoxy, ageing, permeability, oxidation, structural relaxation

This work describes the change of gas permeability of epoxy coatings thermally aged at different temperatures from 50 to 200°C in order to address their barrier properties for protecting concrete in civil engineering industry. Argon permeability characterization tests were carried out on samples either coated on concrete or aged as free standing films. With the increase of time and aging temperature, epoxy becomes more and more permeable and its barrier properties are lost. For better understanding those results, possible ageing mechanisms were investigated. Plasticizer loss was studied by gravimetric analysis and by differential scanning calorimetry. It seems to induce only moderate consequences on barrier and mechanical properties. Reversely, thermal oxidation was shown to severely damage the barrier and mechanical properties due to the existence of chain scissions. Last, structural relaxation ageing is shown to play a negligible role on the investigated time scale but its consequences at longer time remain to be fully understood.

INTRODUCTION

Epoxy resins are widely used in the civil engineering sector. It is a material easy to process and apply. Epoxy resins can be used as a coating and repair resins. Numerous studies have been carried out to quantify the longevity of these materials [ 1 , 2 , 3 ]. However, these epoxy resins are subject to severe environmental constraints: temperature, UV and physical ageing and possibly presence of rainwater (which is not addressed in this paper), all those constraints being at the origin of epoxy failure [ 4 , 5 , 6 , 7 ]. Given the high complexity of those superimposed ageing mechanisms, it is important to distinguish the critical mechanisms occurring in service conditions.

Epoxy resins are subjected to qualifications tests to check they meet the requirements of practitioners. They usually consist in ageing at 70 or 80°C monitored by mechanical tests with durations up to 200 days [ 8 ]. They are however only few evidences that such tests reflect that properties of epoxy resins will last enough. The effect of physical and chemical ageing on mechanical properties was already addressed in the literature [ 9 ] but their effect on epoxy permeability properties remains barely known. These properties are of key interest since epoxies are aimed at protecting concrete from carbonatation reactions for example. In other words, a decrease in permeability may induce severe consequence with degradation of concrete.

The permeability values are well documented for many semi crystalline polymers being for example used as food packaging [ 10 ] and some structure relationships involved in predicting permeability are also available [ 11 ]. They are much more scarcely documented in the case of epoxies [ 12 , 13 ]. At last, the effect of ageing on permeability was scarcely addressed, to the best of our knowledge. According to Gardette et al. [ 14 ], the permeability of a PET film is improved after photo-oxidation, possibly because of a crosslinking mechanism or maybe crystallization induced by aging. The case of epoxies is thus interesting for several reasons: epoxies are amorphous polymers which mainly undergo chain scission during their chemical ageing [ 15 ].

The aim of this present work consists in investigating the effect of ageing mechanisms being at the origin of failure (either in terms of mechanical or barrier properties) during epoxy use namely (i) the physical ageing by structural relaxation, (ii) the loss of plasticizers (plasticizers being used to allow curing the resin in its entirety at room temperature) and (iii) the thermal oxidation. For that purpose, epoxy coatings were aged at several temperatures and argon permeability tests were carried out on samples. Argon was preferred to CO2 because it is an inert gas (with no possible reaction with epoxy and subsequent diffusion reaction coupling phenomena) and is closer to an ideal gas which simplifies the exploitation of experimental measures of permeability. Its lower molecular size [ 16 ] makes a finer probe of barrier properties of epoxy since, basically, CO 2 will diffuse slower than Argon. In the same time, physicochemical characterization will be performed so as to investigate the occurrence of each sort of ageing and its consequences on permeability properties.

EXPERIMENTAL 1. Materials and curing conditions

Epoxy resin was obtained by mixing a prepolymer of DGEBA type together with a hardener mixture containing triethylene tetramine mixed with a cycloaliphatic diamine hardener. This industrial epoxy system contains also contains benzylic alcohol used as a plasticizer to improve the processing and the curing [ 17 ] in practical conditions typically encountered in Public Works field.

Several kinds of samples were studied as described in Table 1 and Figure 1. They were obtained by blending the two-part components (epoxy prepolymer + amine hardener) and casting it so as to obtain the desired shape. The curing was checked by DSC (Q10 apparatus -TA Instruments) at 10°C.min -1 for free standing films given in Figure 1). Curves were acquired to ensure no residual curing exothermal peak was observed at the end of this process (Fig. 1). Glass transition of the unaged samples was acquired both with DSC at 10 °C/min and DMA at 3 °C/min and 1 Hz, and will be part of a later discussion on plasticization. According to Figure 1, it can be concluded that samples are almost fully cured after 48 h at room temperature so that no post curing was added. Since efficient for thin films, the same curing protocol was followed to manufacture thicker samples to control the diffusion-limited oxidation (DLO) phenomenon with ageing temperature and time. Large disks of about 10 mm thickness were cut in small bricks of about 5x5x10 mm 3 and aged at thereafter described temperature and time conditions. Besides, thin samples of 20-25 μm were cut from blocks of epoxy resin (previously cured for 48 h at ambient temperature) using a Leica microtome with a SiC blade.

Ageing conditions

For the chemical ageing (namely thermal oxidation) study, samples were thermally aged at 80, 100, 120, 160 and 200°C in AP60 ventilated ovens (Systèmes Climatiques Service, France).

For plasticizer loss, two kinds of ageing were performed -in situ ageing in TGA cell (described below on paragraph 3.5.)

-ageing in oven monitored by gravimetry For the structural relaxation, the sample, about 10 mg encapsulated in a DSC pan, was heated up and held 1 min at 200°C to erase any previous thermal history. Then the sample was cooled down to the aging temperature T ag , aged isothermally for aging times t ag ranging from 0 to 6000 min under nitrogen atmosphere, and finally cooled down to 0°C. All ramps were performed at 10°C min -1 . For ageing times exceeding 6000 min, the sample was annealed at controlled temperature in a furnace.

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Characterization methods

FTIR spectroscopy

FTIR spectroscopy in transmission mode was carried out using a Frontier spectrophotometer (PerkinElmer) by averaging 8 scans at resolution 4 cm -1 between 400 cm -1 and 4000 cm -1 . Absorbances were measured by subtracting baseline and defined as the maximum height of characteristic peaks.

Tensile tests on thin samples

Mechanical properties of epoxy-amine thin samples were followed by tensile tests using an Instron® 4301 machine on at least five samples per exposure condition. Atmosphere temperature was regulated at 23°C, and testing was carried out with a crosshead speed of 1 mm/min.

Microscopic observation of oxidized layers

After ageing, the brick samples were set in 40 mm diameter cylindrical moulds, then soluble acrylic resin provided by MX-MET was poured onto them to obtain large cylinders of about 2 cm thickness easier to further process. Samples were polished using MecaTech 334 automatic polishing machine with abrasive papers of grades up to 1200. Optical changes of the sample through ageing were visually assessed using a LEICA M80 microscope. Pictures were taken at x2.5 magnification with the same light intensity to properly discern colour changes.

Differential Scanning Calorimetry (DSC)

Differential Scanning Calorimetry (DSC) was performed with the Perkin Elmer ® DSC 8500 at 10 °C min - 1 from 0 to 200 °C. Nitrogen was used as a sweeping gas at a flow rate of 20 ml/min. The temperature calibration was performed using indium and benzophenone as reference standards for melting temperatures. The calibration of energy was done using the enthalpy of fusion of indium.

ThermoGravimetric Analysis (TGA)

20 mg samples placed in a platinum pan were continuously heated at a 10°C min -1 rate under a pure nitrogen flow (20 ml min -1 ). Measurements were performed using a Q50 apparatus (TA Instruments) driven by QSeries Explorer. Data were processed using TA Analysis software.

Plasticizer loss

Plasticizer loss was monitored for 1 mm plates (initial mass close to 2-3 g). Those latter were regularly weighted after ageing using a Mettler Toledo XS105 Dual range balance.

Permeability

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P r e p r i n t n o t p e e r r e v i e w e d

The permeability tests were carried out on steady flow test method in a hydrostatic cell under confining pressure (see Figure 2). During the permeability measurement, the hydrostatic stress on the material was maintained with confining pressures (P c ) of 3 MPa being applied with a Gilson pump. The gas (Argon) injection pressure (P i ) was set to 1.5 MPa using a gas injection device. At first, the gas was injected in R 1 from a big gas tank, the valve C 1 was closed when P i reached 1.5 MPa, and valve C 2 , C 3 , C 4 and C 5 remained open. When the gas flow was steady, we close valve C 5 and record an increase P 0 in comparison with P 0 (atmospheric pressure) within a t by connecting a Keller Barometer and a computer, which allows the flow rate Q 0 at downstream to be calculated. Using Darcy's law, the gas permeability K g can be computed as:

(

) 1
where µ is the viscosity of argon (2.2 10 -5 Pa•s), L is the length and A is the cross-sectional area of the sample. ) (

RESULTS

Barrier properties of epoxy coated concrete

2 2 2 0 0 o i g P P LP A Q K  



This preprint research paper has not been peer reviewed. Electronic copy available at: https://ssrn.com/abstract=4396968 P r e p r i n t n o t p e e r r e v i e w e d Those experiments were completed by ageing concrete coated with epoxies assemblies at 50 ,80 and 100°C (pictures are given in supplementary informations-1). Characteristic values can be commented as follows:

-for unaged samples, values of permeability of concrete coated epoxies are observed to be close to 10 -20 m². This value is consistent with the mixture law:

𝑥 𝐴 + 𝑥 𝐵 𝑃 = 𝑥 𝐴 𝑃 𝐴 + 𝑥 𝐵 𝑃 𝐵 (2)
Where x A and x B are the thicknesses of A and B layers (being on the order of 0.05 m for concrete, and 0.0005 m for epoxy) and P A and P B their respective permeability being on the order of 10 -17 m² for concrete (2.5910 -17 m 2 for the concrete used in this work) [ 19 , 20 ] meanwhile the permeability of epoxy is about 10 -22 m² (see the value for unaged sample in Figure 3). Using Eq. 2, one sees that for unaged sample, the permeability of concrete + epoxy is 10 -20 m 2 , which is exactly the value observed in Figure 4 for unaged sample.

Here also, during ageing, the value of the permeability increases. For ageing at 100°C, the final value of permeability of epoxy + concrete becomes on the order of the value for pure concrete. The permeability of coatings aged at 80°C is multiplied by almost 10 after 70 days meanwhile at 50°C it does not significantly change after more than 30 days.

After ageing at 100°C, epoxy coating was removed and permeability was measured to assess the changes in concrete. Obtained values ranged between 4.6910 -17 m 2 and 6.4910 -17 m². Using those values in Eq. 2 with 10 -22 m² for epoxy layer, the obtained result is about 10 -20 m 2 , as for unaged epoxy coated concrete. In other words, it is impossible to describe the changes observed in Figure 5. It means that degradation of the barrier properties observed in Figure 5 is induced by the epoxy layer itself, consistently with observations given in Figure 4. Therefore, we dedicate the following paragraphs to the analysis of the epoxy behavior.

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Mechanical properties of aged epoxy

Stress strain curves were recorded for virgin and aged materials. Changes of mechanical properties were recorded for various ageing temperatures (80, 100 and 120). As depicted in Figure 5a for data at 120°C, thermal ageing induces (i) a slight increase in elastic modulus and (ii) a decrease in stress at break and in maximal (ultimate) strain associated to a decrease of the volumic energy (i.e. the area under stress strain curves). Ultimate strain is an excellent tracker of oxidation induced embrittlement. Its values are also presented in Figures 5c and5b for 80 and 100°C ageing respectively. It is observed that, even when ageing time is sufficient to induce the loss of barrier properties, there is no strong change of the mechanical behavior.

This preprint research paper has not been peer reviewed. Electronic copy available at: https://ssrn.com/abstract=4396968 P r e p r i n t n o t p e e r r e v i e w e d (see Figure 7) and green ones to plasticized epoxy before and after ageing;

Since the embrittlement (linked to cracking) can be excluded as a reason for the loss of barrier properties, several other processes associated with ageing will be investigated in the following of this paper, allowing to determine which ones are critical for barrier properties.

Plasticizer loss

Anisothermal TGA measurements of virgin (formulated with plasticizer) epoxy resin are presented in Figure 6. A first mass loss is detected at temperatures around 100°C. It corresponds to the plasticizer loss (about 6% of the total mass). The residual mass stabilizes at temperatures around 250°C but decreases abruptly at higher temperatures due to the decomposition of epoxy network [ 21 ]. A similar experiment was conducted on a sample that was purified from its plasticizers (by an isothermally treatment at 160°C under vacuum prior to TGA experiment). This second experiment only shows the decomposition of the epoxy network at 350°C, and confirms that the first mass loss for "virgin epoxy resin" (at 200°C) phenomenon was ascribed to the loss of a plasticizer.

This preprint research paper has not been peer reviewed. Electronic copy available at: https://ssrn.com/abstract=4396968 P r e p r i n t n o t p e e r r e v i e w e d It was previously shown that the loss of plasticizer has a minor effect on mechanical properties on free standing unaged samples [ 22 ]. It is however possible that plasticizer loss may affect the resistance in the case of aged samples. That is the reason why we investigated the kinetics of plasticizer loss either in situ using TGA cell (on 20 µm thin films) or from gravimetric measurements consecutive to ageing in oven (on 1.5 mm thick plates). Independently on the ageing temperature, the plasticizer loss occurs faster in TGA for thin films, since it is not controlled by diffusion.

For aging at 120 °C, the plasticizer loss in thin films is almost total after t < 10h leading the sample mass to reach a plateau, estimated about 6% of the total mass, in consistency with anisothermal TGA measurements. This duration is slightly longer for thick samples i.e., about 2 days (Figure 6) with a slightly lower plateau. At 100°C, in the case of thick plates, the residual mass reaches a plateau at about 200h. Thus, the residual mass does not evolve from 200 to 1000h ageing. Regarding mechanical

This preprint research paper has not been peer reviewed. Electronic copy available at: https://ssrn.com/abstract=4396968 P r e p r i n t n o t p e e r r e v i e w e d properties, the ultimate strain at break was constant for this aging duration. Regarding barrier properties, the permeability continued increasing from 200 to 600h aging whereas the plasticizer loss is considered total after 200h aging. In other terms, there is no obvious correlation between the plasticizer exudation and the loss of macroscopic properties at this aging temperature. We hence concluded that plasticizer loss cannot be considered as a possible reason for loss of barrier properties in the following. Interestingly, when the plasticizer has been totally removed from the material, the glass transition increase has modified the state of the material at the aging temperature of 80 °C (Figure 7). Indeed, it moved from the rubbery state to the glass transition domain. Thus, after the plasticizer loss, the structural relaxation ageing could not be ignored.

Study of structural relaxation ageing

Structural relaxation is detected through the DSC overshoot at the glass transition (Figure 8), from which the ageing advancement can be estimated. The enthalpy of recovery associated to the physical ageing of the sample was calculated by integrating the difference between the scans of an aged sample and a sample with a nil aging time:

∆𝐻(𝑇 𝑎𝑔 ,𝑡 𝑎𝑔 ) = ∫ 𝑇 2 𝑇 1 [𝐶𝑝 𝑎𝑔𝑒𝑑 (𝑇) -𝐶𝑝 𝑛𝑜𝑛-𝑎𝑔𝑒𝑑 (𝑇)]𝑑𝑇 (3)
Where T ag is the ageing temperature, t ag is the ageing time, C p aged (T) and C p non.aged (T) are the heat flows of the aged and non-aged samples, respectively, which are normalized to both sample mass and heating rate in order to be expressed in units equivalent to specific heat capacity. T 1 and T 2 are temperatures arbitrary chosen, beyond the start and ending of the glass transition respectively, and for which the curves of aged and unaged epoxy are perfectly superimposed.

This preprint research paper has not been peer reviewed. Electronic copy available at: https://ssrn.com/abstract=4396968 P r e p r i n t n o t p e e r r e v i e w e d The data confirm the existence of this ageing mode below the glass transition (T ag = 50°C), but also in the glass transition vicinity (T ag = 80°C). Indeed, as previously reported, the relaxation dynamics are heterogeneous enough to allow the structural relaxation of the glassy fraction in a sample which is not completely vitrified [ 23 ]. On the other hand, at 120 °C and 160 °C, the sample is in the liquid state and does not undergo the structural relaxation ageing. Structural relaxation was investigated for several durations up to 1000 h (Figure 9). The enthalpy overshoot value increases and calls for the following comments:

-at 80C, H tends towards an asymptotic value which would be characteristic to an equilibrium state.

-At 50°C, H increases but remains well below the theoretical asymptotic value given by

H  = C P (T g -T ag ) (4)
Where c P is the heat capacity jump when crossing the glass transition.

This preprint research paper has not been peer reviewed. Electronic copy available at: https://ssrn.com/abstract=4396968 P r e p r i n t n o t p e e r r e v i e w e d At 80 °C, the structural relaxation ageing can be considered as a quick process, initiated after about 100 min and over after 2000 min. It is worth reminding that these durations are not representative of real conditions because the structural relaxation is only possible after the plasticizer loss is complete. This means that the time needed to expulse the plasticizer which is very long at 80 °C on thick samples has to be added to the duration of the relaxation process. In other terms, the occurrence of the structural relaxation may coincide with the loss of the barrier properties.

Nevertheless, some arguments seem to contradict this idea. By comparing the data of the enthalpy of recovery recorded after ageing at 50 °C and 80 °C, the energy excess minimized within the experimental time is of the same order, following the same kinetic profile, whereas the loss of barrier properties is only observed when the ageing is performed at 80 °C. Moreover, the structural relaxation aging consists in a decrease of the specific volume, leading to a densification of the material, which is much more expected to decrease the permeability. A crack generation caused by the embrittlement of the system is still possible, as the mechanical properties are clearly impacted by the relaxation, but we can assume that such cracks would have led to a more brutal loss of the barrier properties. Finally, at 80 °C the minimization of energy is of weak amplitude contrary to what could happen at 50 °C where H  is higher.

It would have been of high interest to investigate in more details the impact of structural relaxation at 50 °C. However, as shown in Figure 9, this leads to inaccessible experimental times to fully cover the process. Besides, even if this set of data recorded for early times suggests a linear dependence of H with log (t ag ), the possibility to transpose this dependence to the conditions of use, i.e., at lower temperatures, is far from ascertained. By decreasing temperature, the molecular mobility also decreases, so the kinetics of structural relaxation are slowed down. This last fact is illustrated by Figure 10 where H is plotted versus T ag for t ag = 300 minutes. The curve displays a bell shape with a maximum. At low temperature, the glassy polymer is far from the equilibrium state. As a consequence, the major part of the relaxation is not covered, and the ageing features remain mostly unknown at low temperatures.

This preprint research paper has not been peer reviewed. Electronic copy available at: https://ssrn.com/abstract=4396968 P r e p r i n t n o t p e e r r e v i e w e d Figure 10. Enthalpy of recovery versus aging temperature for 300 minutes annealed samples.

Thermal oxidation

Since the physical structural consequences of aging, i.e., the free volume reducing, seem hardly compatible with a decrease of the barrier properties, chemical reactions have to be considered. During the ageing of thin films of epoxy resin, chemical changes can be classically observed by FTIR (Figure 11) with the appearance of new absorbances centered at 1740 and 1660 cm -1 . Their nature was recently reviewed in literature [ 24 ]. Amides are the main oxidation trackers and their appearance should come from the oxidation of methylene groups in -position of nitrogen atoms. This preprint research paper has not been peer reviewed. Electronic copy available at: https://ssrn.com/abstract=4396968 P r e p r i n t n o t p e e r r e v i e w e d

Maximum absorbances of characteristic peaks between 1625 cm -1 and 1800 cm -1 were used to calculate concentrations of C=O carbonyl groups using the Beer-Lambert law:

A = ε • l • c ( 5
)
where A is the maximum absorbance measured, ε the molar attenuation coefficient at the considered wavelength (in L.mol -1 .cm -1 ), l the thickness of studied film samples (in cm), and c the concentration of chemical groups (in mol.L -1 ). Molar extinction coefficients for amides was assessed using values from previous studies: 574 L.mol -1 .cm -1 at 1660 cm -1 [ 25 ]. It was previously shown that their appearance correlates well with progressive depletion of mechanical properties [START_REF] Fonseca | Imidazolium ionic liquids as fracture toughening agents in DGEBA-TETA epoxy resin[END_REF]. Kinetic curves for amide build up are thus given in Figure 12a for several ageing temperatures. The characteristic times for reaching various level of amide concentration are plotted in the Arrhenius diagram in Figure 12b. It clearly proves that at 50°C, there is almost no oxidation in the timescale investigated in Figure 4.

DISCUSSION

Let us start by discussion on the possible phenomena responsible for the alteration of the epoxy coated concrete. At temperatures below 100°C, as observed from the absence of significant changes in permeability values (see Figure 5), concrete can be considered as stable and the changes in properties can be discussed either in terms of:

-Structural relaxation at glassy stage, i.e., below 50°C for plasticized resin and about 70°C for resin having lost its plasticizer.

-Plasticizer loss -Thermal oxidation (at all temperatures).

Regarding the structural relaxation, we observe, that permeability properties are almost unchanged after more than 2000 h ageing at 50 °C (in conditions where plasticizer loss and oxidation are negligible in the timescale under investigation meanwhile Figures 8-10 show the existence of a significant structural relaxation process). It suggests that structural relaxation poorly influences the barrier properties. This result is not so surprising: physical ageing is usually associated with a reduction of free volume. It is already documented that free volume decreases with crosslink density [ 26 ] and that an increase of crosslink density induces a decrease of solubility and diffusivity [ 27 ].

It is however impossible to conclude that structural ageing will have no effect on barrier properties at higher conversion degrees than those observed in Figures 8-10, at which structural relaxation may induce the embrittlement of epoxy (the epoxy glass being far from equilibrium at 50 °C, the minimization of specific volume continues during its whole service life), and then a catastrophic failure of its barrier properties. Moreover, the "coupling" of structural relaxation and oxidation was never investigated to our knowledge. In other words, the consequences of the sum of both ageing remains to be investigated.

Another question is the possible responsibility of structural relaxation in the barrier property loss observed at 80 °C. As previously mentioned, relaxation at both 50 and 80 °C has led to similar enthalpy loss, while barrier properties have differently evolved within the considered experimental time. These results, combined with the expected increase of barrier properties under the free volume reducing, explain why we do not assume the structural relaxation to be the main component behind the permeability variations.

The possible influence of plasticizer loss seems easier to discuss at 100°C.According to Figure 6b, plasticizer is lost after 200 h of ageing for a 1 mm thick plate. In the same time, Figure 3 and4 show that that barrier properties are barely increased in the early ageing time corresponding to plasticizer loss, and continue to degrade significantly more at longer time, where oxidation starts to become significant. In other words, oxidation seems the most plausible explanation to the loss of barrier properties.

Let us now turn to oxidation, which is expected to be the only possible cause of failure at 100°C. Oxidation is in essence a heterogeneous phenomenon described by the reaction diffusion coupling of oxygen. Bulky samples are oxidized in surface, whereas deeper layers are less degraded. The thickness of oxidized layer is given by:

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𝑇𝑂𝐿 2 = 𝐷 𝑂2 .[𝑂 2 ] 𝑟 𝑂𝑋 (6)
Where TOL is the thickness of oxidized layer, D O2 the oxygen diffusivity, [O 2 ] the equilibrium oxygen concentration (i.e., at the surface of a thick sample) and r OX the oxidation rate. The sum of activation energy of oxygen diffusivity and solubility is lower than the value for oxidation rate so that TOL increases when lowering temperature [ 28 ]. At 200°C, the thickness of oxidized layer is about 150 µm (see Supplementary information -2 ). It can hence be considered that samples under investigation (presented in Figure 4,[START_REF] Ernault | Origin of epoxies embrittlement during oxidative ageing[END_REF][START_REF] Van Krevelen | Properties of Polymers -Their Correlation with Chemical Structure; their Numerical Estimation and Prediction from Additive Group Contributions[END_REF][START_REF] Celina | Oxygen diffusivity and permeation through polymers at elevated temperature[END_REF] are almost homogeneously degraded.

In such samples, the assumption can be made that end of life (in terms of mechanical properties or permeability properties) is associated to a « critical » chemical state [ 29 ] which can be interpreted from the oxidation mechanism (Scheme 1): the hydroxypropyl ether groups responsible of sub-glassy mobility is progressively destroyed. Its disappearance provokes the depletion of the  relaxation amplitude (and thus an increase in elastic modulus) together with the loss of mobility and thus of plastic deformation.

Scheme 1. Simplified oxidation mechanism of epoxies.

Let us now turn on the consequences of ageing in terms of barrier properties. At first, it can be recalled that some previous papers showed that permeability was decreased after oxidation [START_REF] Gardette | Impact of photooxidative degradation on the oxygen permeability of poly(ethyleneterephthalate)[END_REF], which is, in appearance, in contradiction with our data, but was observed in the case of other polymer systems than epoxies. It is also well established that TETA group favors chain scission [ 30 ] creating empty space where oxygen can more easily diffuse. At 80°C or 100°C, the permeability of epoxy coated concrete is drastically increased. It calls for the following comments:

 It remains speculative to directly correlate permeability changes with amide concentration in the epoxy. It seems actually that the degradation of the permeation properties is faster for the concrete + epoxy than for the epoxy alone. According to Eq. 1, an increase of epoxy permeability by a factor 2 induces an increase of epoxy concrete by a factor 2. However, when looking at permeability values after 500 h, one sees that epoxy permeability is multiplied by almost 3 meanwhile permeability of concrete + epoxy is multiplied by a 1000 factor, i.e., the permeability of epoxy coated concrete is very close of the value expected for concrete alone. This preprint research paper has not been peer reviewed. Electronic copy available at: https://ssrn.com/abstract=4396968 P r e p r i n t n o t p e e r r e v i e w e d k Let us assume that a common amide concentration value describes an end of life criteria: for instance, 0.25 mol l -1 corresponds to a severely degraded epoxy at 80°C (with permeability multiplied by a decade) and even more degrade at 100°C (where barrier properties of epoxy are almost completely vanished). The extrapolation of time to reach this concentration to lower temperature remains challenging, having in mind that the use of Arrhenius law for lifetime value is discussable (Figure 12b).

CONCLUSIONS

This paper deals with the multiscale study of the complex ageing mode of epoxy coatings with a focus on the reasons responsible for the loss of barrier properties. For that purpose, epoxy concrete coatings were aged together with some thin plates.

It was mainly shown that physical ageing by structural relaxation, and/or loss of plasticizer had a very limited effect on mechanical and barrier properties. On the contrary, oxidation (even if slow) can provoke the embrittlement of coatings.

It remains now to investigate the effect of coupled ageing, in particular where structural relaxation occurs on oxidized samples. The existence of chain scission may alter the macromolecular mobility, the rate of relaxation and the nature of the equilibrium state, i.e. finally the effect of ageing on mechanical and permeation properties. Reversely, the effect of structural relaxation and/or plasticizer loss on the oxidation rate is worth to be investigated. At last, in order to get closer of real conditions, the effect of humid ageing on barrier and mechanical properties should also be investigated.

ACKNOWLEDGEMENT

The Agence Nationale de la Recherche is gratefully acknowledged for funding the project ANR DUREVE (ANR 18-CE06-0028 -2019-2022), and this work.

Figure 1 .

 1 Figure 1. DSC thermograms (1 st heating) of epoxy uncured resin and epoxy networks after several curing cycles (48 h at room temperature, 48 h at room temperature + 30 min at 170°C).

Figure 2 .

 2 Figure 2. Schematic diagram of steady flow test device.

Figure 3

 3 Figure 3 depicts typical changes of permeability of epoxy disks after thermal ageing at 100 °C. The value of single epoxy foil is close to 10 -22 m² [ 18 ]. During ageing, it is clear that barrier properties are severely damaged.

Figure 3 .

 3 Figure 3. Changes of permeability versus time for epoxy resin after ageing at 100°C.

Figure 4 .

 4 Figure 4. Changes of permeability of epoxy coated concrete after ageing at 100, 80 and 50°C.

Figure 5 .

 5 Figure 5. Changes of mechanical properties for epoxy resin thermally aged at 120°C (a), changes of elongation at break for ageing at 100 (b) and 80°C (c). Blue symbol corresponds to unplasticized resin(see Figure7) and green ones to plasticized epoxy before and after ageing;

Figure 6 .

 6 Figure 6. Thermogravimetric analysis of virgin (plasticized) and purified epoxy resin (a) and plasticizer loss during isothermal ageing of plates under air monitored by gravimetry or TGA (b).

Figure 7 .

 7 Figure 7. Effect of plasticizer loss on glass transition.

Figure 8 .

 8 Figure 8. DSC traces of epoxy resin aged at 50 and 80°C with appearance of enthalpy overshoot.

Figure 9 .

 9 Figure 9. Enthalpy of recovery versus ageing time for epoxy resin.

Figure 11 .

 11 Figure 11. FTIR spectra for the carbonyl region for epoxy resin aged at 80 (a) and 100°C (b) under air.

Figure 12 .

 12 Figure 12. Changes in amide concentration for ageing at 200, 160, 120 and 80°C (a) and Arrhenius diagram of characteristic times for reaching concentrations in oxidation products, the values being given in caption (b).

Table 1 .

 1 Description of samples under study.

	samples	manufacturing	Test			picture
	cylindric blocks about 1	casting of 2 parts components	microscopic observations	SI
	cm thick	in aluminium cups	for oxidized layer value
	20-25 µm films	microtomed from blocks	FTIR, structural relaxation	6-12
			ageing, plasticizer loss by
			TGA and gravimetry
	H4 dogbones samples	casted in Teflon mould	tensile test		5
	0.5-1.5 mm thick disk	Casted into a Teflon mold and	Thermal	ageing	3, 6
		stored 12h at 21 °C	monitored	by
			permeability
			measurements	and
			plasticizer loss
	concrete coated with	casting in wood mould.	Ageing at temperatures	4
	epoxy (epoxy thickness	Concrete with a ratio W/C: 0.5.	lower	than	100°C
	about 300-500 µm)	Brush application for epoxy	monitored	by
		coating	permeability
			measurements

This preprint research paper has not been peer reviewed. Electronic copy available at: https://ssrn.com/abstract=4396968 P r e p r i n t n o t p e e r r e v i e w e d


domain: shs sde

text:
Anna Karlsdóttir

Jean-Michel Huctin

Jeanne-Marie Gherardi

Tanguy Sandré

Jean-Paul Vanderlinden

Working with and for Arctic communities on resilience enhancement

Concepts like knowledge co-production and narrative-centred approaches have become more prominent in place-based research in the Arctic. This article will share experiences from the Belmont Arctic II program's project "Sense Making, Place attachment, and Extended networks, as sources of Resilience in the Arctic" (SeMPER-Arctic, 2019-2023). Rooting our work in the Arctic, with and for Arctic communities, we collected local stories of changes, shocks, upheavals, and their aftermaths in three communities: Uummannaq and Ittoqqortoormiit (Greenland) and Tiksi (Sakha Republic, Russia). However, this article is primarily about our research in Greenland. We investigated the interactions between the local narratives of resilience and two broad categories of external narratives: environmental science, and public policy and regional development. We developed a narrative-centered, locally rooted, place-based understanding of resilience. This calls for developing tools and strategies to increase community resilience in other communities and for sharing the lessons learned with regional planners and policymakers. We contribute to the framing of global environmental change through respectful, non-prejudiced enquiry, deciphering what it means to be a resilient community. Therefore, the results of this analysis are meant to be translated into options for actions, at the local, regional, national and circumpolar levels. Working towards maximizing impacts or enhancing resilience from research conducted for the benefit of communities involved in the research requires reflexivity and relationship building. How did this commitment emerge in our research practices? How do we meet ethical considerations? How do we contribute to decolonizing research whose imperative is towards culturally responsive research? This article will discuss experiences, questions and tensions emerging from circumpolar fieldwork-grounded research.

Introduction

Research in Arctic indigenous communities focusing on the effects of climate change is less than thirty years old (Folke et.al, 2002;[START_REF] Cruikshank | Glaciers and Climate Change: Perspectives from oral traditions[END_REF][START_REF] Gunn | Introduction: A Perspective from the Humanities-Science Boundary[END_REF]. Although natural science research on climate change is based on a tradition that goes back well over a century (Arrhenius, 1893), it is only in the last two decades that the wider world has become convinced that the Arctic is one of the regions of the world where the effects of climate change are visible to the naked eye, resulting in an unprecedented level of international interest. However, research that focuses on and works with communities has until not long ago been at the margins, especially related to knowledge co-production or transdisciplinary research [START_REF] Vanderlinden | Meaning in the face of changing climate risks: Connecting agency, sensemaking and narratives of change through transdisciplinary research[END_REF]. Grossly a decade ago, community adaptation to climate change had accelerated and concepts such as resilience and sustainability had come to the forefront (i.e., Folke et.al., 2002;Einarsson et.al., 2004;Rasmussen, 2011, Petrov et.al., 2016). Since then, a large body of literature focusing on Arctic communities has emerged.

Until recently there was little research on how co-production research works in practice and what its implications are, especially regarding how data collection and analysis can be developed to increase the quality and reliability of research. However, we currently need to foster our understanding on how Indigenous partners can be more deeply involved in other stages of research such as project design and dissemination of results, and more generally the roles that researchers themselves play in shaping research. A recent surge in this literature demonstrates co-productions' relevance to social science research. This is especially true to sustainability issues, which are characterized by extensive uncertainty and complexity (for example [START_REF] Wibeck | Co-creation research for transformative times: Facilitating foresight capacity in view of global sustainability challenges[END_REF]Yua et.al., 2022). In addition to this experience, in many cases, new demands from public administration on registering time reduce creativity and open repeated dialogues with communities, sometimes driven by financial resource constraints. Increased demands for ethical contracts when working in Indigenous communities have arisen from bitter experience of strong exploitation practices in the past among academics and other scholars. These demands have developed in different parts of the world over the past 15 years, although they appeared later in the Arctic (see for example among Inuit Nunaat: Inuit Tapiriit Kanatami, 2018;Inuit Circumpolar Council, 2021, Inuit Circumpolar Council, 2022). This article presents important practical lessons drawn from the co-authors' experiences in several research projects in Inuit communities in Greenland, particularly during the SeMPER-Arctic 1 project. Many articles promote the co-production of knowledge, but at the level of principle, without always proposing concrete answers to the problems faced by researchers.

The three focus communities are quite different, but they share some common challenges due to adverse conditions related to remoteness. Remoteness from regional and national political centers reduces the power of local people to make decisions about their own present and future. Some of them have problems with dilapidated housing (whether due to weathering or lack of resources for maintenance); increased uncertainty about weather forecasts and ice conditions; and changing ecosystems due to challenging climate conditions. Towns are also losing population (with the exception of the population of Uummannaq, which has stopped decreasing due to the relocation of residents from two settlements that were evacuated after their definitive closure following a 1 Sense Making, Place attachment and Extended network as sources of Resilience in the Arctic tsunami in 2017). The level of development of social infrastructure is a constant challenge. While hunting is still a livelihood, commercial fisheries are of greater economic importance. These three communities are emblematic of the challenges of adapting to climate, economic, political, and cultural changes. While the weather has become warmer and more erratic, sea ice has tended to decrease in thickness and extent, at least over the past two decades. These three communities are striving to find ways to remain sustainable and attractive despite their remoteness at a time when urbanization is a megatrend (Rasmussen, 2011).

Initiation of Research Project and the Inclusion Process

The first challenge facing scientific projects is the search for funding, which raises the question of the possible involvement of local Indigenous partners in the preliminary co-design of projects. To avoid asking too much of them without any guarantee of success, or to avoid disappointing or fatiguing them in the event of repeated failure, it is often easier for researchers to involve them little or not at all in the writing phase of the application file intended to respond to the call for projects. However, if the application is selected, the lack of input from the local partner (or at least without validation of the project as written in the application) means that researchers run a great risk of having designed a project that is partly unfeasible, or of no real use to the community studied, or even not really wanted by the local partner. To avoid this often-unavoidable pitfall of most foreign projects, researchers need to have acquired some local knowledge and, of course, to have built up a solid relationship of trust with their partners. This is not a given for all teams of foreign researchers, especially those who are new to the field and have no previous experience of working in the community under study. In the case of our SeMPER-Arctic project, we relied on letters of support from local partners with whom we had previously discussed and agreed on the project's objectives. Our first Greenlandic partner, accustomed to working with researchers, had worked with one of us for many years, while the second partner had been met by a team member during an initial reconnaissance trip; as for the Yakut partner, we worked together into several projects (ARTisticc, Belmont Forum funding, and Nunataryuk, H2020 funding), this for now almost 10 years. Without these established professional relationships, some of which were also personal friendships, it would have been impossible to design a project that was in any way connected to the local community.

Like many other international projects focusing on the Arctic, we were funded through a large global or interregional initiative, in this case the Belmont Forum Arctic II initiative, which was supported by ten national research councils, for three years. The call aimed at bringing together researchers and other expertise across the globe to develop proposals from integrated teams of scientists and stakeholders to address key areas of Arctic resilience, from understanding to action. This collaboration of academic and non-academic knowledge systems constituted a transdisciplinary approach that would advance not only understanding of the fundamentals of Arctic resilience but also spur action, inform decision-making, and translate into solutions for resilience (Belmont Forum, 2019). The consortia had to address at least two of seven interconnected elements of resilience as described in the Arctic Resilience Report of the Arctic Council (2016): natural, social, financial, cultural, and human capitals; infrastructure; and knowledge.

SeMPER-Arctic was one of eight proposals awarded funding, which is provided through the national research councils of partners (Belmont Forum 2020). Many of us had experience from conducting prior research within the circumpolar Arctic as human geographers, engineers, anthropologists, economists, and climatologists, to mention few of our disciplinary backgrounds. The integration across scientific disciplines enables us to consider multiple worldviews present in contemporary science (Mauser et.al., 2013). This interdisciplinary group was needed as the purpose of the project was to analyze how the two external narratives (environmental science and regional development policy ones) interact with local narratives of resilience to assess their impacts. The objective was to develop a narrative centered, locally rooted, place-based understanding of resilience within Arctic communities. As such resilience and narrative analysis were the central framework in SeMPER-Arctic, which was meant to contribute to the knowledge base on global environmental change through locally guided enquiry of what it means to be a resilient Arctic community in the 21st century.

As put forward in the Arctic Resilience Report synthesis (Arctic Council 2016, Arctic Council 2017), decisive action is needed to effectively navigate emerging conditions to avoid potentially negative social and ecological changes already emerging. One of the major statements not only in this report, but also echoed by various politicians and representatives in the Arctic Council, is that "responses will be most effective if they build on a well-integrated, evidence based interdisciplinary understanding of Arctic social-ecological systems and their relationships with global processes and draw on Indigenous knowledge wellgrounded in practical experience" (Arctic Council, 2017;2).

Research evidence shows that scientific representations and interpretations have emerged as dominating worldviews (Bremer et.al., 2017). While sciences are necessary, their research objectives and measurement tools can often be too abstract, and their metrics can be very unfamiliar to human populations in general. This domination of "western" science has created a significant undervaluing of the traditional knowledge perspective, which has demonstrated its effectiveness in assessing weather, climate, and navigating natural environments for human communities. Therefore, it has to be our common enterprise as researchers and population to rediscover the places we inhabit; it is not the responsibility of the expert community alone to reinterpret our places under a changing climate (Ibid, 2017).

The Way Knowledge Co-production has been Conceptualized

Many of the problems that societies around the world are currently facing need to be tackled with a different mindset from the ones that created them. Thus, there is an urgent need for new ways of thinking that go beyond dominant disciplines and paradigms, exploring contemporary issues, insights, and responses. In policy discussions as well as in research, there are increasing calls for societal transformations, which are systemic, long-term, non-linear change that spans the different sectors of societies. Formal conventional knowledge systems like those practiced by universities and research institutes may be failing humanity. Especially when the impact of the research is measured against the level of progress in stimulating the societal changes needed to address challenges like climate change (Fazey, 2019[START_REF] Fazey | Transforming knowledge systems for life on Earth: Visions of future systems and how to get there[END_REF]. This urges researchers to have an integrity when conducting research to secure their work is relevant to the communities involved. Ideally, knowledge co-production is a demanding approach in conducting research that involves deep collaboration between researchers and stakeholders who have different types of knowledge, expertise, and perspectives. It recognizes that multiple forms of knowledge, including scientific, local, Indigenous, experiential, and contextual knowledge, can contribute to all stages of the research process, and aims to integrate these diverse forms of knowledge to generate more relevant, robust, and actionable research outcomes (Mauser et.al., 2013).

In knowledge co-production, researchers and stakeholders work together as equal partners, engaging in a process of co-design, co-implementation, and co-interpretation of research (Wibeck, Eliason & Neset, 2022). It may involve collaborative activities such as joint problem identification, research design, data collection, analysis, and interpretation of findings. This approach emphasizes the importance of mutual respect, shared decision-making, and open communication among all participants throughout the research process. It recognizes that stakeholders, who may include community members, policymakers, practitioners, or other end-users of research, are not just passive subjects or recipients of research findings, but active contributors who bring their own insights, experiences, and expertise to the table.

It often includes iterative feedback loops, where stakeholders provide ongoing input and guidance to researchers, and researchers respond by adjusting their research questions, refining their methods and their data analysis. It also includes their participation in field work, by helping researchers access observation situations or by facilitating the collection of oral data, sometimes by carrying out the collection itself as for example during the COVID-19 period in 2020-2021 in which researchers could hardly travel. The process aims to generate research outcomes that are contextually relevant, applicable, and useful for addressing real-world problems, and that reflect the perspectives and needs of diverse stakeholders.

Given the need for co-creation, surprisingly little discussion has evolved around its implications for research practices and knowledge co-production i.e., what challenges you meet in fulfilling the promise of co-creation (Ren, Johannesson & van der Duim, 2018). As mentioned before, unnecessarily burdening local partners, and raising the expectations of research funding during proposal design and submission can lead to disappointment and deteriorate trust with the researchers if funding is not approved.

The question then is how can researchers contribute and impact the processes of, for example, enhancing resilience? One may expect that researchers wanting to increase impacts in or for communities need to become "insiders" to a higher degree [START_REF] Hjemdal | Doing Research on, for and with Tourism Organizations during innovation processes[END_REF]. However, this is complicated when international research teams are involved. This may also mean that knowledge transfer is more complex if researchers want to contribute with impacts which would require skills far beyond their disciplines. This also implies the more or less long time to build relationships of trust and the possibility or reciprocal desire to take time together, which is not given to everyone.

A major challenge with implementing Co-Production of Knowledge is mischaracterization (i.e. referring to collaborative work as CPK). For example, a researcher may identify a problem, develop research questions, and then invite Indigenous participation in the project. The project may result in Indigenous participation through collaboration on information collection or other aspects of the research process, or there may be a capacity building aspect to the work. This theoretical type of relationship, through the lens of our framework, would not be considered co-production because involvement or equity at all stages of the process was not the aim, methodology, or the outcome. The mischaracterization of CPK does not advance equity for Indigenous Peoples and their communities in research relationships, project outcomes and limits a fuller understanding of the world (Yua et.al., 2022).

Despite good intentions, the climate change knowledge co-production literature is a complex meeting place of several academic traditions and practices, introducing both ambiguity and creativity as scholars' appropriate perspectives from neighboring disciplines. Scholars have thus used several ways in applying and understanding the term co-production. Of the eight ways identified by [START_REF] Bremer | Coproducing "post-normal" climate knowledge with communities in northeast Bangladesh[END_REF], our project includes perspectives to facilitate extended modes of science that integrate societal knowledge and values, building adaptive capacity in institutions and to empower traditional knowledge systems. Hence, we would ideally like the results of the work to find its way into a structured science-policy interface, but this is yet to be seen.

Ethics towards Community-Focused Research

Several different approaches stress the inclusion of local communities in research development and in dealing with the rapid environmental and social changes ongoing in the Arctic. Various methods may relate to climate change research (i.e. [START_REF] Hansen | Benchmarking af miljøvurderingslovgivning for olieaktiviteter i Grønland: Bilagsrapport 2-Opsamling fra Workshop 2 (Benchmarking of environmental assessment legislation for oil activities in Greenland)[END_REF] and seek to assess cross-regional societal development (i.e. Karlsdóttir et.al, 2017). Participatory scenario approaches have been credited with many positive outcomes that include identifying important benefits like social learning across different stakeholder groups, promoting community-owned solutions, and facilitating the sharing of experiences in a creative and collaborative way [START_REF] Oteros-Rozas | Participatory scenario planning in place-based social-ecological research: Insights andexperiences from 23 case studies[END_REF], Nilsson et.al, 2019).

We have, as an interdisciplinary team, varied experience of working in knowledge co-creation research. One of us has worked for three years with participatory foresight analysis in 12 communities in the Nordic Arctic where collected results were shared with local communities in citizen meetings, with regional and national authority representatives and with interregional bodies in special workshops (Karlsdóttir et.al, 2017). This methodology does not enhance a co-creative knowledge approach and includes certain weaknesses, such as the research may lack diversity among the participants and lack follow-up on whether the process led to any action (Nilsson et.al, 2019). However, this form of action research was a collaborative process which required partnerships, dialogue, and cooperation with various actors on multiple local, regional, national, and inter-regional levels, and where results had the potential of being mobilized into policy actions.

We were challenged in the first 18 months of the three-year process due to consequences of the global pandemic and related sanitary policies and travel restrictions. For the most part, we could not visit the communities that were the focus. However, the partners doing fieldwork in Tiksi (Sakha Republic) collected instances of events that the local population found important, and gathered explanations that local people and authorities gave to these events, their origin, their management and their short-and long-term consequences (Nikulkina, Shadrova & Antonova, 2020, Nikulkina et.al., 2020). Then another shock hit us: we lost contact with our Russian partners after the war against Ukraine started in 2022. Yet we have proceeded with processing the data already collected in the Sakha republic [START_REF] Doloisio | Analyse des impacts sociaux et culturels de la fonte du pergélisol dans la côte de l'Arctique Russe: cas d'étude de Tiksi et Bykovsky/Analysis of the social and cultural impacts of permafrost thaw in the coastal Russian Arctic: Case of Tiksi and Bykovsky[END_REF], but it has truly affected reciprocity relations between the communities, and therefore knowledge co-production as well. Thus, our account in this article is primarily focusing on the Greenlandic research sites and communities.

Involved researchers and partners focusing on Greenland had to come up with alternative ways of conducting research in the first phases (luckily, we were granted an extension to 2024 due to the pandemic). This required, as all research endeavors, reflexive ways of conducting research. The consortium communicated for the first two years through TEAMS or Zoom and made a serious effort to build up collective reflexivity (Palaganas et.al., 2017) but also collected data (interviews conducted by local partners). One important point of departure was that you cannot do research only to benefit your own merit as a researcher if you engage with a community. This felt even more urgent since the focus of the project was on resilience in the wake of shocks, upheavals or incidences related to climate change driven effects.

SeMPER-Arctic works across disciplines and analytical levels in that it examines narratives driven by a natural science perspective, the political scene (manifesting in national and regional strategies and policies), and with three local communities in combination (Uummannaq, Ittoqqortoormiit and Tiksi). In all the research locations we had key local partners who proved crucial in making field research possible and without whom we would not have been able to do the work. Acknowledging their role is an important ethical aspect of community focused research. We stress an approach that fosters wellbeing and inclusive societies in an era of climate change and uncertainty; our project is fundamentally about the process of spatialization and becoming space as we adapt "a thinking that one cannot write sufficiently in the name of an outsider" (Deleuse & Guatarri 1987[START_REF] Huijbens | Developing Earthly Attachments in the Anthropocene[END_REF]. Thus, researching and understanding the process of the ongoing changes in the communities reveals how manifold the community is as well as the entities in it. By revealing how entities emerge from the relations that compose them, they are not to be pulled apart but seen in connection, which involves understanding and making sense of the community while recognizing how power relations are entangled into power geometries inherent in the transformation process [START_REF] Huijbens | Developing Earthly Attachments in the Anthropocene[END_REF].

Environmental changes make up space for stories. Our narrative-based research requires that it is grounded in the lived experience of communities.

Long term Relationships and Trust

One major factor in enabling participatory or co-production of knowledge in practice is to build trust through long-term relationships. Relationships are crucial for co-production (Kielsen [START_REF] Holm | Etude de la glace de mer et des peuples de l'Arctique dans une approche de co-production du savoir[END_REF]UNESCO, 2009) and Indigenous research (Smith, 2021: 137). Building trust means sustaining long-term relationships that exceeds the demarcated period of funding for a research project, both prior and post research activity (Gearheard et.al., 2006;Mahoney et.al., 2009;Mahoney et.al., 2013).

Relationships and trust are needed in encounters with the community, especially to bridge the work with the community and for the community. One of the researchers had 18 years of research experience over 26 years of traveling to the community of Uummannaq and in Greenland which secured firm relationships with the key partners who conducted part of the data collection. With their deep insights and knowledge, we were better equipped to understand and mediate what stories of upheavals, shocks and transition were more important than others. Engaging with key partners who have 37 and 30 years of experience working with young people and children on empowering them in meaningful activities intersecting nature and culture helps to enable trust. Working with children and youth has also been important [START_REF] Huctin | Børn på tynd is[END_REF][START_REF] Huctin | Maltraitance et bientraitance des jeunes au Groenland : de l'éducation traditionnelle inuit (XVIIe-XXe siècles) à l'actuelle maison d'enfants d'Uummannaq[END_REF]Huctin et.al, 2021;[START_REF] Gregersen | Livsmod-Socialpaedagogi og psykoterapeutisk behandling af børn i Grønland[END_REF]Karlsdóttir & Jungsberg, 2015;Karlsdóttir et.al., 2019). "A key strategy for navigating the inevitable tensions that can arise in projects where research on resilience is in focus with natives is paying continual attention to relationship building and mutual acknowledgement of the value added by all the invested members" (Wexler et.al., 2020).

The relevance of addressing and acting upon decolonizing approaches to social science research with communities is important and relevant for Greenland. A prominent and vivid discussion expressed in music and arts, in public and social media forums and among contemporary Greenlanders is focused on the ails of colonialization implications and post-colonialism. With many Greenlanders being of mixed ethnicity, the discussion becomes even more complex [START_REF] Thisted | Blame, Shame, and Atonement: Greenlandic Responses to Racialized Discourses about Greenlanders and Danes[END_REF]. When it comes to the need for political agency, it is evident that the majority looking for self-rule are of Greenlandic origin. However, the leading positions within society are still occupied by Danes, who thereby have a strong influence on the decision-making processes [START_REF] Björklund | The postcolonial relationship between Danes and Greenlanders in contemporary Greenland -A phenomenological study of identity forming in a postcolonial context[END_REF][START_REF] Grydehøj | Navigating the binaries of island independence and dependence in Greenland: Decolonisation, political culture, and strategic services[END_REF]. Colonial identity forming of lived and imagined experience plays a role on many levels, but also breaking out of it, is both an important signifier and mindset for many young adult Greenlanders (i.e., Uyarakq's "Move I'm Indigenous" provocative lyrics: "Like a fire make your demands… we manifest your tears because we are the true pioneers…" (Uyarakq, 2020). Greenlanders are well aware that they belong to a small community and self-determination is important for them, in being recognized as such and as people (Kleist in [START_REF] Björklund | The postcolonial relationship between Danes and Greenlanders in contemporary Greenland -A phenomenological study of identity forming in a postcolonial context[END_REF]. They are proud of their heritage and have many reasons to be [START_REF] Bjørst | Climate Testimonies and Climate-Crisis Narratives. Inuit Delegated to Speak on Behalf of the Climate[END_REF]. In some cases, Greenlanders in power have struggled holding influence over the climate change debate touching Greenland in international settings. Thus, they have blamed global discourses as too academically constructed, leaving their role as limited to acting as victims of global climate change effects [START_REF] Bjørst | Climate Testimonies and Climate-Crisis Narratives. Inuit Delegated to Speak on Behalf of the Climate[END_REF]. This starkly contradicts many Greenlanders self-perceived role, as they express certain autonomy in their relationship to nature built on centuries long heritage of coping and adapting to a harsh climate (Abelsen in [START_REF] Bjørst | Climate Testimonies and Climate-Crisis Narratives. Inuit Delegated to Speak on Behalf of the Climate[END_REF]. Mastering the environment may in some cases display Greenlanders' character (Beyer Broch, 2020). One of the critiques that have been linked with research conduct is that Greenland has been seen through Danish eyes. It is claimed that they see it to a greater extent as an empty terrain than a populated nation when it comes to scientific research. Furthermore, that it is more important for Denmark, what they as a nation can get out of researching the ice sheet than thinking about involving the population to whom the ice belongs [START_REF] Sommer | Danske forskere bør inddrage grønlaendere i projekter i Grønland. Videnskab[END_REF]. This underpins the importance of recognizing multiple forms of knowledge in research conduct.

What do the Ethical Guidelines Require? Epistemologies that have Changed! One of the papers guiding the ICC Ethical and Equitable Engagement Synthesis Report (2021) states that past inequities persist in the form of inequitable research processes and relationships across the Arctic (Yua et.al, 2022). These inequitable processes and relationships, which prioritize non-Indigenous ways of being and knowing, feed a structure of decision making that does not fully account for Indigenous Peoples' knowledge, perspectives, or needs [START_REF] Yua | A framework for coproduction of knowledge in the context of Arctic research[END_REF]. From our point of view, scientific conduct needs to adapt to changing epistemologies where embedded practical experience is recognized as an important element in the knowledge generation.

In the EU context, one particularly important recent step towards anchoring decolonial research in the Arctic is the new Roadmap to Decolonial Arctic Research (Herrmann et.al., 2023).

ICC encourages researchers to practice the co-production of knowledge and follow Inuit guided processes to successfully bring together Indigenous knowledge and science, while ensuring that our knowledge is trusted and respected as a unique knowledge system that comes with its own evaluating and validation processes. Of paramount importance in their guidelines is that research projects should avoid that results of their work burden the people in focus (ICC, 2021). ICC stresses eight ethical protocols for research conduct that they recommend as a good pathway, which we attempted to fulfill in our research practices (see text box above: Inuit Circumpolar Council, 2021). They warn about cherry-picking their protocols, but overall, they stress reciprocity in the cooperation process with Indigenous communities. ICC stresses that their guidelines should not overshadow national guidelines and that these protocols do not replace any local, regional, or national guidance provided by Inuit (Inuit Circumpolar Council, 2021: 13).

The Greenland Research Council was established in 2013 and started to function in 2014. One of their primary roles besides allocating funding is to improve and strengthen Greenlandic research embedded in Greenland and to strengthen research relations internationally and within the commonwealth (Inatsisilorneq, 2013;Mercer et.al., 2022). They have been working on developing ethical guidelines and recently published their National Research Strategy towards 2030 (Ministry for Education, culture, sport & church, 2023). Their approach involves being open to the international scientific community while safeguarding their own interests and values (Greenland Research Council, 2020). Their view is that more than ever, there is a need for a joint research effort that can address questions related to global processes, climate change and the green transition, which contributes to sustainable development in Greenland: Unfortunately, we see examples of Greenlandic research institutions and other stakeholders being involved far too late in foreign research projects. It undermines the possibilities for a genuine, equally dignified cooperation for the benefit of both parties. It is crucial for good cooperation that all involved parties are involved from the start of a project, where the basis for ownership is established -ownership of the knowledge that is created and influence on and participation in how it is used. Therefore, the Greenland Research Council works purposefully to develop Greenlandic research policy and support network formation and other mechanisms through which Greenlandic and outside researchers can exchange ideas and interests, jointly develop research questions, and become familiar with institutions and infrastructure (Greenland Research Council, 2022;4).

As described previously, we who are engaged in the SeMPER-Arctic project made the continuous effort to involve our local partners at an early stage and during the process of the work. We have also committed ourselves to the convening of discussions about emerging knowledge while we have been in the field. This has been our way of approaching equitable involvement and recognizing that people are part of the community and ecosystem. Being challenged by the pandemic made us even more reliant on our local partners who conducted part of the qualitative research.

In our case, it was pivotal to have the support, cooperation, and network of the Uummannaq Polar Institute before the work began. We also consulted experts from Ilisimatusarfik/University of Greenland researchers at early stages in the literary work phase when collecting public reports, strategies, and plans, to analyze and assess political narratives in Greenland related to climate change and resilience (Jungsberg et.al., forthcoming). At later stages, we consulted Greenland Research Council and various other stakeholders of knowledge generation in Greenland, as well as fellow researchers within social science and Circumpolar Arctic research activities. In this process it has been very important to get back and forth to our key partners in the communities to hear their opinions. In Ittoqqortoormiit, which was a new community for the project researchers, seven fieldwork trips of three to nine weeks were implemented by three of the co-authors between September 2021 to July 2023. Building strong trust was crucial for our research team, formal interviews (over 30), participant observation, and informal discussions have been sustained remotely and locally from 2020. This considerably extended the involvement of stakeholders and community members over the time, allowing to build community-based research. Even if we acknowledge the limits of the involvement of community members in the project design and in the research conduct itself, an important step towards inclusive and fair research practices has been reached. Using an inductive approach, the research team identifies central invisibility of narratives regarding the essential importance of narwhals for the community and the threat to the future of narwhals hunting. In June 2023, a 22-minute short film was coproduced in the native language (Tunumisut, Ittoqqortoormiit). Various community members have been involved at different stages (production, edition, story-making, translation/transcription, voice-over, and video caption).

A first projection was held throughout a culturally relevant event ("kaffemik" or celebration party with coffee/tea/cakes). Additionally, a diffusion throughout local Facebook page was implemented. We reached at least a third of the community (cumulation of attendance to "kaffemik" and reactions on Facebook), while opening to comment and opinion. Among the main reactions that were generated, people expressed gratefulness, desire for the film to be spread out, and happiness to see the story exposed. Ittoqqortoormiit's born community members who live abroad also expressed feelings of homesickness, which strongly resonate with the expression of place-attachment we frequently encountered during our time in Ittoqqortoormiit. Important work is also carried out towards reframing sea ice changes in a salient perspective for community members (Sandré et.al., forthcoming).

The Dialogue that Nuances our Knowledge

All these practices require dialogue with informants and partners in the community that in most cases is voluntary. So, we must respect their time and seasonal activities that may not correspond to our ideal needs, but we simply must adapt as researchers. Researchers who have been trained into certain terminologies and logics need to step up and widen their horizon and engage in meaningful partnerships for both parts. This can be challenging for some but liberating for others and requires skills beyond academic training. Intercultural competence in communication helps, as well as mastering the local language which in our case is only partly fulfilled (one researcher masters Greenlandic, two other master Danish, many master Norwegian and French, all including local partners communicate in English).

The knowledge co-production approach goes beyond "participatory" or collaborative research that could be limited in terms of involvement of local populations. Adopted by a small minority of researchers around the world, the knowledge coproduction approach has recently been on the increase. In addition, to be more respectful to studied people and to research partnership requirements advocated by Indigenous leaders, it would offer new sources of data and better analyses. It would also foster a deeper public awareness and hopefully inspire more effective public policies [START_REF] Baztan | Life on thin ice: Insights from Uummannaq, Greenland for connecting climate science with Arctic communities[END_REF].

We try to ensure that the knowledge gained is of value to the community -extending the meaning of research conduct to work with and for the communities. One aspect of that is being in contact with local and regional actors who make decisions or execute decisions and plans in the towns on behalf of the municipality in different fields.

As the project has not been completed at the time of writing this article, we still have much to do, in particular to ensure the most complete restitution of this co-produced knowledge to the communities involved who are most interested in it.

Meaningfulness for Communities -Conclusion and Discussion

In the early days of research on Indigenous communities, the rapid societal changes from huntergatherer lifestyles to modernity were prominent in the perspective of social scientists. The recognition of the power of traditional knowledge to understand the complex dynamics has been slow to emerge. While vulnerability to these changes was the forefront perspective to begin with, the focus shifted to trying to understand the adaptive capacities of communities and their ability to navigate and cope under changing circumstances. Pearce et.al. (2009), for example, have identified in a comprehensive review the importance of targeted vulnerability research that collaborates closely with community members and decision makers. This included understanding the interactions between current and projected climate change, as well as the factors which determine vulnerability and influence adaptation, identifying research gaps and making recommendations for advancing adaptation.

The commitment to work not only with the communities but also for communities in producing research-based knowledge can be seen as our small step in research based decolonialization and culturally responsive research. As proposed by [START_REF] Sultana | The Unbearable Heaviness of Climate Coloniality[END_REF], we mobilised a narrative-based approach whereby lived experiences can counterbalance hegemonic framings that structures climate coloniality. Maximizing impacts or enhancing resilience is something that we promised in the research proposal.

Our good will, however, faces a dilemma. Do communities really benefit from our research? Translating results to business concepts may not necessarily be a useful outcome for the community. We should rather strive to translate these findings into a resilience enhancement framework where people with long-term knowledge from within the community are our best allies in interpreting what can be targeted and strengthened. It may be an emergency response framework, it may be social infrastructure, it may be improving port capacity and renovation of man-made structures, it may be recycling, it may be fair and environmentally friendly tourism, or it could be all of it.

With increasing research on how co-creation research plays out in practice and what its implications are, there are still important gaps in terms of how to equitably fund a project, conduct data collection and analysis, and disseminate results in full collaboration with community partners. These gaps must be addressed to increase the quality and reliability of the research, and to change the roles that researchers themselves play in shaping the research and its findings. We do not claim to have navigated perfectly but rather to have tried to set some examples in reciprocal encounters with the communities in question.

Our SeMPER-Arctic project comes to an end in 2024. We have therefore not reached the project completion and do not know if we will be able to translate our findings to something that can really be beneficial to communities in the long run. But we foresee that the relations with the communities will not be terminated by the formal termination date the research funders have set.

Beyond co-producing knowledge and caring for local stories that we write in the accumulating literature on climate change and the impact on communities, time will tell how we succeed.

The idea and practice of knowledge coproduction has become an important and new perspective for Arctic research as a response to the recent increase of research projects with ethical rules and participatory/collaborative approaches. Furthermore, it is required by Indigenous leaders and recommended by organizations such as the Arctic Council, UNESCO, IPCC, and others. The immensity, speed and complexity of the ongoing challenges require the best available knowledge for decision-making and there is growing recognition that this can revitalize local culture, empower the community and foster sustainability. There is a greater understanding that traditional and scientific knowledge are complementary, or rather that they can be complementary.

We would like to argue that our work so far has been characterized as collaboration towards coproduction (which means it is not full knowledge co-production but a sincere attempt to achieve fair collaboration). We are not insiders and cannot be because we are not part of the Arctic communities. But as researchers, we can collaborate with our Indigenous partners by finding the best possible form for each according to the conditions of the place and time in order to address complex issues and try to lead to innovative solutions. We have in our own work seen how it becomes easier with the development of information and digital technologies (photo, video, audio, internet, and social networks). Science can benefit from Indigenous Peoples' experience of their own environment and in-depth understanding of the complexity and interconnected environmental systems. The collaboration provides another source of information and data: daily observations at the local scale all year round. It provides relevant information about livelihood, community concerns, needs and values. It offers the multiplication of perspectives. Research with knowledge co-production leads to information that meets users' needs and is considered salient, legitimate, and credible by them. Through the confidence it inspires in the communities, the coproduction approach is more likely than other forms of research to have an impact on society. But it often remains more of an ideal towards which to strive throughout the entire research process than the form required at the start of this process.

To improve the movement from collaboration to co-production, we still need to answer some questions on challenges and potential conflicts. Before the research is kicked off, researchers must reflect on how they perceive the inclusion of Indigenous knowledge in their research work, which is sometimes constrained by administrative rules, and, for their part, Indigenous partners must reflect on what scientific knowledge can support their community. What are the expectations of both parties? How can they concretely share knowledge for their mutual benefit? It also remains a question how western scientists may choose such an approach when they know so little about Indigenous knowledge. Furthermore, one may wonder how Indigenous Peoples can be interested in collaborating with researchers if they do not know them well enough, when they are not familiar with the functioning of sciences as practiced by Western researchers and when there is a distrust of their effectiveness or their desire to bring a benefit?

On the other hand, researchers can do much to improve the trust placed in them during research.

For example, what kind of relationships are needed to improve connections before and during fieldwork, as well as after? How can we connect the global scale (science knowledge and interest) with the local scale (Indigenous knowledge and needs)? We may also ask ourselves how to make sure that all partners respect all steps in the co-production process. When the research is completed, we need to ask ourselves how to involve and credit Indigenous partners in our dissemination work and what kind of knowledge should be returned to Indigenous communities. Finally, those essential questions remain food for thought to design better research in the future.

Figure 1 .

 1 Figure 1. Degrees of Integration: Research & Praxis (Johnson, 2013).

Acknowledgments

This work was carried out as part of the SeMPER-Arctic (Sense Making, Place attachment and Extended Networks as sources of Resilience in the Arctic) project, funded by the Belmont Forum. The authors would like to warmly thank their local partners Ann Andreasen (Uummannaq) and Mette Pike Barselajsen (Ittoqqortoormiit) for their invaluable contribution to this research work and of course all members of the Arctic communities involved in the project.