Tailoring The Surface Structure Of Polypropylene Fiber And The Properties Of Fiber Reinforced Composite

Polypropylene(PP)fiber,as one of the five most popular synthetic fibers,has excellent properties such as light,high strength,good elasticity,wear resistance,corrosion resistance,electrical insulation and warmth retention.Although the industrialization of PP fiber started late in China,it has developed rapidly in recent years and has been widely used in industry and life.Its high strength and other characteristics have made it a large demand for reinforcement materials in the fields of construction and textiles.However,the surface of the PP fiber is smooth,and there are no polar groups on the PP molecular chain,which makes it difficult to combine the matrix with the matrix as a reinforcing phase in the composite material.Therefore,how to improve the bonding between the PP fiber and the matrix becomes the key point of current discussion.In our previous researches,the micro rheological behavior of PS as the dispersed phase in the shear flow field and the tensile flow field during blending melt spinning was studied in detail.The formation and evolution of morphology of PP / PS blended fibers was clarified.The formation mechanism of gradient structure in PP/PS blended fibers was proposed,and found fibers with different gradient structures has different surface morphologies.Based on the previous research,PP and PS were taken as the research objects in this paper.The micro-rheological behaviors of the dispersed phase are tailored by adjusting the viscosity ratio of the component and the content of the PS dispersed phase.A variety of morphologies were built on fiber surface.The effect of the dispersed phase morphology in the fiber matrix on the mechanical properties of the fiber is studied.The single fiber extraction experiment was performed to evaluate the bonding of the fiber in the composite.The relationship between fiber surface structure and fiber / resin interface bonding property are also studied.The specific research content and results of this article are as follows:(1)Morphology control of blend fiber: Based on the analysis of dispersion phase and fiber surface morphology,the influence of viscosity ratio and PS dispersion phase content on morphology of blend fiber was studied.When the viscosity is low(0.2-0.5),the dispersed phase forms a droplet structure in the process of fiber forming.At the same time,the surface migration of the low viscosity PS dispersed phase also makes the fiber surface present irregular and uneven protuberance structure.The more PS content is,the rougher the fiber surface is.When the viscosity ratio is 1,the dispersed phase on the fiber surface is short microfiber like and droplet like,and there are a few short grooves on the fiber surface,When the viscosity is relatively high(~ 3),the dispersive phase on the fiber surface is long and micro fibril,which makes the fiber surface appear long grooves and tend to be orderly.When the PS content is 20%,the dispersive phase size is the smallest,and obvious optical diffraction phenomenon is observed.(2)The mechanical properties of the fibers with different morphology of dispersed phase were studied.When the PS phase in the blend fiber is droplet like(viscosity ratio is 0.2-0.5),the mechanical properties of the fibers are lower than that of pure PP fiber,and the content of dispersed phase has little effect on the mechanical properties of the fibers.When the PS phase in the blend fiber is short microfiber like and droplet like(viscosity ratio is ~ 1),the content of low PS has little effect on the mechanical properties of the blend fiber The mechanical properties of PS dispersed phase are mainly long micro fibrils,and the tensile strength of the blend fiber is significantly improved,with micro fibril reinforcement effect.When the dispersed phase in the blend fiber is long micro fibril structure(viscosity ratio is ~ 3),the mechanical properties of 8% content is the best,and the spin ability and tensile properties of the fiber can reach a better state at the same time.(3)The influence of the surface structure on the interfacial bonding properties of the fiber / resin composite was studied.Although the surface microstructure of the fiber can be changed by adjusting the viscosity ratio,the content of dispersed phase and etching,the bond strength is not fully enhanced with the appearance of microstructure,and the shape of the surface microstructure has a great influence on the bond strength.The improvement of bond strength of single fiber resin composite with long micro fiber structure is lower than that with irregular and uneven protuberance structure on the surface under low viscosity.Among them,the blend fiber with low viscosity and 20% PS content was 196% higher than pure PP fiber,with the best reinforcement effect.The etched fiber with medium viscosity and high viscosity and 20% PS content was 39% and 33% higher,respectively.