Study On Corrosive Aging Resistance Of Silane Coupling Agent Modified BF/VE Composites

Fiber reinforced resin matrix composites have the characteristics of high axial specific strength,specific modulus,light weight,and strong designability,which make them indispensable and important materials in marine resource development and marine engineering construction.However,composite materials used in marine environment will inevitably be corroded and aged by acid,alkali and seawater,etc.The long-term use of composite materials in corrosive aging environment will lead to the degradation of their mechanical properties,which will seriously affect the normal use of composite materials.This study investigates the changes of flexural property and impact property of basalt fiber reinforced vinyl ester resin（BF/VE）composites in water,seawater,high concentration sea water acidic and alkaline environments,which can not only predict the service life of composites in each environment,but also provide theoretical support for the development of composites with corrosive aging resistance.The BF/VE composites were firstly modified with different mass fractions of silane coupling agents KH550,KH560 and A171,and the basalt fiber before and after modification is used as reinforcement and vinyl ester resin as matrix.The basalt fiber reinforced vinyl ester resin composite material is prepared by molding process.The effects of modification with different types and mass fractions of silane coupling agents on the mechanical properties of the composites were investigated and their modification mechanisms were analyzed.Secondly,the composites were immersed in5 corrosive aging environments,including 20°C,40°C,and 60°C water,3.5%Na Cl seawater,10%Na Cl high concentration seawater,10%H₂SO₄acidic,and 10%Na OH alkaline environments for 56 days.The effects of silane coupling agent modification,immersion environment,immersion time,and immersion temperature on the mechanical properties of the composites were studied and the mechanisms of corrosive aging was analyzed.The following conclusions are drawn:（1）The basalt fiber modified by 1%silane coupling agent KH550,KH560 and A171 has the best interface bonding with vinyl ester resin,and the interface bonding performances of the composites are improved.Compared with the unmodified basalt fiber reinforced composites,the flexural strength of the modified basalt fiber reinforced composite increased by 16.71%,14.96%and 13.59%;the impact strength increased by 10.13%,8.84%and 7.41%.（2）The appearance and color of composites will also change differently after immersion in different corrosive aging environments.After immersion in water,3.5%Na Cl sea water and 10%Na Cl high concentration sea water environments,the appearance and color of the composites changed little,but after immersion in 10%H₂SO₄acidic and 10%Na OH alkaline environments,the appearance and color of the composites changed greatly.At the same time,the appearance and color of the composites are greatly affected by the environmental temperature and immersion time.After 56 days of immersion in the acidic and alkaline environment at 60℃,a large number of white spots appear on their surfaces.（3）The mass loss rate of BF/VE composite materials gradually increases with soaking time,while the loss rate gradually decreases with soaking time.As the soaking environment temperature increases,the mass loss rate and rate of composite materials significantly increase.The mass loss of composite materials is most significant in a10%Na OH alkaline environment.According to the"10-degree rule":for every 10degree increase in ambient temperature,the corrosive aging time of composite materials approximately doubles.After soaking in a 60℃alkaline environment for 56days,which is equivalent to soaking at 20℃for 896 days,the mass loss rates of unmodified and modified composite materials with KH550,KH560,and A171 silane coupling agents are 4.825%,3.841%,4.067%,and 4.285%,respectively.（4）The flexural strength and impact strength of BF/VE composites showed a decreasing trend with the prolongation of immersion time after immersing in the corrosive aging environments.The flexural strength and impact strength of the composites decreased rapidly at the beginning of the immersing period,and the rate of decrease basically tended to gradual with the extension of the immersion time.An increase in environmental temperature will significantly increase the degree of corrosive aging of composite materials.When the temperature of the immersing environment increased,the flexural strength and impact strength of the composites decreased significantly,and the temperature increase would accelerate the degradation of the mechanical properties of the composites.（5）The degree of decrease in flexural strength and impact strength of BF/VE composites after immersion in 10%Na OH alkaline environment was the most significant among the five corrosive aging environments.After 56 days of immerion in alkaline environment at 60°C,which is equivalent to soaking at 20℃for 896 days,the flexural strength of the unmodified and KH550,KH560 and A171 silane coupling agent modified composites decreased by 69.24%,50.34%,55.95%and 61.28%,the impact strength decreased by 56.57%,41.35%,45.88%and 50.12%,followed by 10%H₂SO₄acidic environment at 60°C,the flexural strength decreased by 46.34%,34.25%,37.86%and 41.29%,and the impact strength decreased by 38.18%28.33%,31.20%and 33.98%.The retention rates of flexural strength and impact strength of the composites after immersion in seawater environment were not much different from those after immersion in water environment,indicating that the composites has good corrosive aging resistance in seawater.The silane coupling agent modification improved the flexural strength and impact strength of the composites by enhancing the interfacial bonding properties of the composites,and delayed the degradation of the mechanical property of the composites in the corrosive aging environment.Considering the experimental results,the order of modification effects of three silane coupling agents on the corrosive aging resistance of BF/VE composites is KH550>KH560>A171.