Preparation And Properties Of Polyarylate Fiber / Bismaleimide Resin Composites

Advanced resin matrix composites are playing an increasingly important role in many fields of our life with the advantages of small specific gravity,high strength and good thermal stability.Our demand for the performance of the composites is higher and higher.Polyarylate(PAR)fiber is one of the preferred materials for reinforcement because of its wet heat resistance,creep resistance and high strength and modulus;Bismaleimide(BMI)resin has outstanding properties such as processability,high strength,thermal stability,corrosion resistance and creep resistance.It is suitable to be used as the matrix of advanced composites.However,the adhesion between PAR fiber and resin is small,and the brittleness of BMI resin is relatively large,which restrict the popularization of their composites.In view of this,in this paper,the surface of fiber was modified by chemical etching,and montmorillonite was selected to toughen BMI resin.The mechanical and thermal properties of PAR fiber reinforced BMI resin before and after modification were systematically studied.The surface of PAR fiber was etched with acidic KMnO₄ solution.The effects of potassium permanganate and sulfuric acid concentration,etching time and temperature on the properties of fiber monofilament strength,infiltration and interfacial shear strength with resin were studied to determine the best modification scheme.It is shown that the fiber modified by acidic KMnO₄solution has groove surface.At the same time,the oxygen content of fiber surface increases.Therefore,the surface wettability is improved.Under controlled conditions,the fiber damage is small,and the interfacial shear strength with BMI resin is improved.The best comprehensive properties of PAR fiber treated in the solution with KMnO₄ of 4g/L and H₂SO₄ of 10%for 30min at room temperature.The interfacial shear strength between the PAR fiber/BMI resin composite is16.72MPa,which is 51%higher than that of the unmodified fiber/BMI.The retention rate of monofilament strength is about 90%,the surface contact angle is reduced from 116.5°to 74.4°,and there are more surface-active groups.The effect of fiber content on the comprehensive properties of BMI resin was studied,and the mechanical properties of fiber/BMI resin before and after modification were compared and analyzed.It is shown that within the experimental range,the mechanical properties of the composites are significantly improved with the fiber mass fraction.While the mass fraction of fiber is increased from 0%(pure resin)to 6.7wt%,the fracture work increases from 0.08J/m~2 to 4.61J/m~2,the bending strength increases by 106%,the impact strength increases from 3.7KJ/m~2 to 57.2KJ/m~2,and composite maintains its excellent thermal stability.The mechanical properties of the fiber composites were improved to a certain extent after acid potassium permanganate etching,and the tensile properties are improved significantly.For example,when the fiber content is 2.5wt%,the tensile strength increases by 51%.The influence of montmorillonite content on the comprehensive properties of BMI resin was explored,and the changes of comprehensive properties of resin composites before and after montmorillonite modification were compared and analyzed.The results show that the mechanical properties of the modified system increased first and then decreased a little when the content of montmorillonite increased continuously.When the mass fraction of montmorillonite is 4wt%,the tensile strength increases by 97%,the impact strength reaches 8.0KJ/m~2,which is 116%higher than that of pure resin.In addition,the mechanical properties of fiber/montmorillonite/BMI composites are basically improved,the impact toughness is improved most significantly.Its impact strength is increased by 24%,and its excellent heat resistance is maintained.In summary,the PAR fiber significantly improves the mechanical properties of the BMI resin.Modified PAR fiber increases its bonding force with the BMI resin.The impact toughness of the BMI resin after montmorillonite improves.The impact resistance of fiber/montmorillonite/BMI composites is obviously improved,and the excellent heat resistance is maintained.