Surface Modification Of Poly-p-phenylene Terephthamide Fibers And Their Rubber Composites With Reinforced Properties

Poly-p-phenylene terephthamide(PPTA)fibers have advantages of high strength,low density,great stability,corrosion resistance and other excellent performance.Therefore,they have widely used in aviation,spaceflight,machinery,military,petrochemical and other fields.To composite PPTA fibers and rubbers can not only assure rubbers' high elastic,but also improve performance.However,PPTA fibers have smooth surface and low surface reactivity,which causes their bad bonding performance between fiber and matrix,and greatly reduces the composites' properties.Therefore,surface modification of PPTA fiber is particularly important.This paper first studied researched the mechanical properties and adhesive performance of the respectively unmodified PPTA/NBR and PPTA/EPDM composites by dumbbellsample tensile test,rectangular tear test,H pull-out test and scanning electron microscopy(SEM).The results showed that both composites presented small ensile strength,elongation at break,tear strength and H pull out force.SEM observation found that the stretching section and PPTA surface after extraction smooth and not any adhesive rubber,which revealed a weak adhesion between PPTA fiber and rubber.Therefore,dopamine was used to modify PPTA fiber through its strong force to material surface,and mechanical properties and adhesion properties of the composites were studied b The dopamine modified PPTA has rough surface,and the oxygen content increases.SEM image of the stretching section and fiber after drawn showed that there were a small amount of adhesive rubber particles on the fiber surface of dopamine modified PPTA/NBR composites,which indicated an improved adhesion between fiber and rubber.Thus,the dopamine modified PPTA/NBR displayed higher tensile strength,elongation at break,tear strength and H pull-out force than unmodified systems.In order to improve the adhesion further,dopamine-silane coupling agent was used to modify PPTA fiber surface,and their rubber composites properties were also researched.The results showed that surface roughness increased further,the fiber surface presented single blade,and elements' contents and types changed a lot.SEM images of the stretching section and fiber after drawn displayed that much more adhesive rubber was on the PPTA surface,and properties both increased in varying a great degrees.That indicated that the adhesion increased greatly after the modification by dopamine-silane coupling agent,which can be applied to the polar NBR and non-polar EPDM.This method provides new applications of PPTA.