Preparation And Characterization Of Polyimide Surface-treated Glass Fiber Reinforced Epoxy Resin

Glass fiber/epoxy resin composite has characteristics of high strength and easy processing,which is commonly used in aerospace,automotive,construction and other fields.In recent years,the use of polyimide to solve the defects in high-performance composite has become a hot topic.However,the brittleness of epoxy resin cured material limits its application in the field of high-performance composite materials.T his experiment adopted a hydroxyl-containing PI to toughen and enhance the matrix,and studied the curing behavior of the matrix,mechanical properties,thermal stability and toughening mechanisms.Six different kinds of PI modified glass fibers were prepared to study the effect of PI on tensile properties and acid corrosion resistance of fiber tow.According to the non-isothermal DSC test,the curing process of the resin was determined to be room temperature/2 h+70?/0.5 h+120?/1 h+150?/1 h+170?/0.5 h.When the content of PI150 was 0.4%,the modification effect of the matrix was the best.At the same time,the tensile strength,bending strength and fracture toughness of EP-PI150 were raising from 42.1 MPa,65.0 MPa and 1.3108MPa·m^-1/2 of pure EP to 51.5 MPa,79.1 MPa,and 1.4751 MPa·m^-1/2,respectively.The PI-coated glass fiber improved the fiber bundle and tensile strength,and the hydroxyl-containing PI1 coated fiber had the best performance and the tensile strength was 1031.6 MPa.After soaking in a mixed acid solution with p H value of 4.7,the weight loss rate of glass fiber with paraffin removal was the highest,reaching 12.3%,while the weight loss rate of glass fiber treated with PI surface was decreased,PI1-GF was only 2.8%.The short-cut GF?concentrated HNO₃ oxidation treatment?and PI1-GF were blended in the modified matrix to study the effect of different fiber content on the mechanical and thermal properties of the composite.The matrix and composite material with better performance were selected for acid corrosion resistance and hydrophobicity.When the GF content was 0.5%,the mechanical properties of GF/EP-PI150 composites were the best.T he tensile strength,bending strength and fracture toughness of the EP-PI150 increased by 9.36%,9.35%and 1.12%,respectively,and the T g increased by 7.88°C.T he PI coating treatment increased the content of fiber in the matrix.When the content of PI1-GF was 1.5%,the tensile strength and bending strength of PI1-GF/EP-PI150composites increased by 32.56%and 25.87%,and Tg increased by 14.56°C.However,the fracture toughness was best when the PI1-GF content was 0.5%,which was increased by 2.15%.T he acid-resistance test showed that the mechanical properties of the composites gradually decreased with the increase of the soaking time.The mechanical properties of the same set of samples were greatly lost in the wet state,and the mechanical properties in the dry state recovered slightly,but they could not be restored to the initial state.T he corrosion resistance of EP-PI150 and PI1-GF/EP-PI150 composites was greatly improved,and the degradation rate of mechanical properties in the wet state was greatly reduced,and the mechanical properties in the dry state were similar to those in the wet state.T he water absorption test showed that EP had the highest water absorption rate of 2.7%,and the EP-PI150 water absorption rate dropped to0.68%.The addition of 0.5%GF to the modified matrix resulted in only a slight drop in water absorption.When 0.5%PI1-GF was added into the modified matrix,the water absorption of the composite was only 0.46%.