Aging Behavior Of Glass Fibre Reinforced Epoxy Resin Composites In Simulation Oilfield Application Enviroment

As the difficulty of oil and gas extraction increases,fiber-reinforced resin matrix composites for oilfield have been exposed to severe environments such as drastic temperature changes,salt spray,high water content,and high mineralization for a long time,and the mechanism of performance deterioration of composites in special environments in the petrochemical field is not clear at present.Based on that,this research investigates glass fiber reinforced epoxy resin composites commonly used in petrochemical field and simulates the service environment of composites in oil and gas extraction and transmission process through indoor aging experiments,and investigates the aging behavior of composites under high and low temperature cycles and different solution medium conditions.During the molding process of the composites,Multi-Walled Carbon Nanotubes（MWCNTs）and silane coupling agent KH-550 were added to the epoxy resin during material preparation,and the effects of the addition of different mass fractions of MWCNTs and KH-550 on the properties of the composites before and after aging were investigated.The main achievements are as follows.（i）The composites Naval ordnance laboratory（NOL rings）were prepared by physical-mechanical mixing by adding MWCNTs at mass fractions of 0.1,0.2,and 0.3 wt%and KH-550 at mass fractions of 0.5,1.0,and 1.5 wt%to the epoxy resin by winding molding process,respectively.Static mechanical properties,dynamic mechanical properties and load heat deformation were carried out.According to the test results,the composites with 0.2 wt%MWCNTs and 1.5 wt%KH-550 added to the epoxy resin had the best performance respectively.（ii）The prepared composites were subjected to temperature cycling aging experiments to study the degradation mechanism of composite properties upon temperature change.The experimental data showed that the temperature change and continuous high temperature process would cause damage to the resin matrix and interface,and the interlaminar shear strength and tensile strength of the aged composites were reduced to some extent,and cracks were generated on the material surface.The incorporation of different weight percentages of MWCNTs and KH-550 into the resin affected the cracking of the composites surface after aging and improved the preservation of the remaining strength of the composites.（iii）The aging experiments under four conditions of acid salt spray,high-temperature and high-pressure mineralized water,different temperatures hydrothermal and saturated CO₂ solution were carried out to analyze the diffusion actions of ions and water molecules in diverse liquid mixtures and the trends of properties of the composites after aging,and to study the aging behavior of the composites under different media conditions.The mass change rates of the composites under the four media conditions set in this study can be fitted by Fick’s diffusion law.Low temperature conditions and the presence of ions in the liquid mixtures are not advantageous to the diffusion of water molecules.The dispersed action of ions in solution was analyzed by XPS and EDS tests.According to the test results,the amount of ions is higher in the part near the external liquid medium.The osmotic pressure generated by the difference in ion concentration can limit the diffusion of water molecules inside the material,and the number of water molecules gathered in the part near the external liquid medium is higher,and the deterioration of material properties in this part is more pronounced.The diffusion behavior of ions in solution was analyzed by XPS and EDS tests,and it was clear that the degradation of composite properties under different media conditions was mainly attributed to the damage caused by water molecules to the matrix and interface.The degradation of static dynamic mechanical characteristics of the aged materials was observed,while the addition of MWCNTs and KH-550 to the resin matrix prevented the diffusion of water molecules inside the composites and improved the remaining strength conservation rate,which improved material’s aging resistance.After aging,the mechanical properties of the composites show a decreasing behavior.Combined with the microscopic morphology test results,it is clear that the degradation of composite properties under different liquid media conditions is mainly caused by the damage caused by water molecules to the resin matrix and composite interface.The high temperature conditions will accelerate the degradation of composite properties.The addition of MWCNTs and KH-550 to the resin matrix prevented the diffusion of water molecules inside the composites and improved the remaining strength conservation rate,which improved material’s aging resistance.