Study On Comprehensive Performance Of Several High-performance Fibers

The main topic of this study is on the comprehensive performance the following six fibers:Three of PI long fibers (PI-1 and PI-2 belonging to high strength and high modulus type, PI-3 belonging to heat-resistant type), Kevlar fiber, F12 fiber and UHMWPE fiber, three of PI fibers and F12 fiber were formed by wet-spinning, Kevlar fiber were from dry-wet spinning preparation, UHMWPE fiber were prepared by gel-wet spinning.(1) Basic parameters of the fibers:Fineness and density of the fibers were measured by weighing method and densitometer, The density of three PI fibers, Kevlar fiber and F12 fiber were similar (1.43-1.45g/cm3), UHMWPE fiber possess minimum density (0.97g/cm3); Apparent morphology, fracture surface and characteristic structure were analyzed by SEM and FTIR. Many discontinuous hollow in the axial direction were detected on the surface of the three PI fibers and F12 fiber, and a large number of continuous striped groove is on the surface UHMWPE fiber, Kevlar fiber surface is relatively smooth. the cross section of two aramid fibers is split and microfibrillar which disappeared in the cross section of three PI fibers. Because the molecular chain of UHMWPE is still very flexible at low temperature, It is hard to break.The surface morphology and sectionmorphology of fiber are mainly related to the spinning process.(2) Moisture absorption of the Fiber:Through test of moisture regain fiber, their comparative hygroscopicity were researched, Ascending order of moisture regain is that:UHMWPE(0.06%), PI-1(1.24%), PI-2(1.35%), PI-3(1.89%), F12(3.70%) and Kevlar(4.5%).(3) Contact angle and surface energy of fiber:Through static and dynamic contact angle test, three kinds of PI fibers and UHMWPE fiber are more hydrophobic, their contact angle are similar(101°-108°); the contact angle of F12 fiber is 80° and have maximum surface energy; Kevlar fiber possess highly hydrophilic (contact angle is 0°).(4) Antistatic property of fibers:antistatic properties of fibers were characterized by fiber specific resistance tester, UHMWPE is most easy to generate static electricity with highest specific resistance, and PI-3 fiber have the optimal antistatic properties(5) Mechanical properties of the fibers:Tensile properties, creep properties, surface friction properties of fibers were tested through a single fiber strength tester and yarn dynamic friction coefficient tester. Results showed that, the tensile properties of F12 fiber is the most outstanding with high strength (4.45Gpa) and modulus (96Gpa), and the strength and modulus of PI-1 and PI-2 is greater than 3GPa and 80Gpa slightly; Creep resistance of PI-1, PI-2, F12 and Kevlar were relatively superior, PI-3 and UHMWPE fibers have creep phenomenon; Decreasing order of Surface dynamic friction coefficient of fibers is that:F12, PI-3, Kevlar, UHMWPE, PI-1 and PI-2.(6) Thermal properties of fibers:Thermal stability, dynamic mechanical properties, thermal dimensional stability and heat aging properties were studied for the comparison of thermal performance. Results showed that three kinds of PI fibers exhibited the most outstanding thermal stability, thermal dimensional stability and heat aging performance, thermal stability properties of Kevlar fiber is better than F12; Tg of PI-1, PI-2, PI-3, F12 and Kevlar is at 318℃,324℃,407℃, 250℃ and 280-290℃ respectively.(7) Acid and alkali resistance properties of fibers:The change in the mechanical property retention and molecular structure of fibers before and after acid or alkali treatment were investigated, UHMWPE fibers possess the most outstanding acid/alkali resistance, acid resistance of PI fibers are outstanding, but the alkali resistance is relatively poor; a certain loss in mechanical properties of F12 and Kevlar fibers appeared after the treatment of acidic or alkaline solution.