| Thermotropic liquid crystalline polyarylate(TLCPAR)fiber has the advantages of excellent mechanical properties,heat and moisture resistance and chemical resistance,so it has a wide potential application value in aviation,military,sports and other fields.However,TLCPAR fiber has fewer chemically active groups on the surface,low surface free energy,and weaker interaction with the resin matrix,resulting in poor interface shear strength of the fiber/composites,it is necessary to take effective modification to TLCPAR fiber surface treatment.Silane coupling agent can not only react with the hydroxyl group on the fiber,but also with the epoxy resin.Therefore,three methods of plasma,silane coupling agent and plasma-assisted silane coupling agent were used to treat the fiber in this paper,and the interfacial bonding property between the fiber and epoxy resin was studied.In this paper,the surface of TLCPAR fiber is treated by oxygen low-temperature plasma processor,and using a scanning electron microscope,strong monofilament elongation tester,automatic video micro-contact angle measuring instrument and microsphere debonding instrument testing method to analyze and discuss plasma treatment on the surface morphology,mechanical properties,wettability,interfacial adhesion properties between TLCPAR fiber and epoxy resin matrix,and the surface elements of TLCPAR fiber under oxygen plasma treatment were further studied by EDS.The experimental results show that in a short time under low power,obvious etching cracks appear on the surface of the TLCPAR fiber,the fiber surface makes rough,the fiber’s body properties are not damaged,and the fiber’s wettability is somewhat improvement,decreases from untreated 106.1 ° to 78.4 °,and the interface shear strength of TLCPAR fiber / epoxy resin matrix increase by 40% after oxygen plasma treatment.In addition,the timeliness of plasma was investigated and it was found that the effect of plasma treatment will decay with time,and eventually stabilize.In the second part,the effect of silane coupling agent treatment on the surface structure and properties of TLCPAR fiber was discussed.The interfacial shear strength between TLCPAR fiber and epoxy resin was studied with the mass fraction,reaction temperature and reaction time of the silane coupling agent,and the optimal treatment condition of the silane coupling agent KH-560 was determined by orthogonal test.The experimental results show that when the mass fraction of the silane coupling agent is 30%,the reaction temperature is 30°C,and the treatment time is 10 minutes,the optimal treatment condition is achieved.The interface shear strength of the TLCPAR fiber and the epoxy resin matrix is increased from 5.18 MPa to 8.04 MPa,an increase of 55%.Comparing the unmodified TLCPAR fiber with the fiber under the optimal modification conditions,it is found that the surface roughness of the fiber is increased,the fiber’s body properties are not damaged,and the contact angle between the fiber and water is reduced from 106.1° to 89.5°.The performance becomes better.The Si element on the surface of TLCPAR fiber is analyzed by EDS and infrared spectrometer,and it is proved that the silane coupling agent is introduced into the fiber surface.Based on the above results,TLCPAR fiber was modified with oxygen plasma-assisted silane coupling agent surface to introduce active groups on the surface of TLCPAR fiber,and the effects of untreated,single treatment(oxygen plasma treatment or silane coupling agent KH-560 treatment)and composite treatment were compared and analyzed.The results shows that the surface of TLCPAR fiber changes from smooth to rough and is accompanied by granular material.The mechanical properties of the fiber body are not damaged.Fiber wetting is better than single treatment.The interfacial shear strength between TLCPAR fiber and epoxy resin matrix is 10.16 MPa,which is 96% higher than the original sample. |
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