Study On Ultrafine-CaCO₃/PP Composite Fiber

Polypropylene(PP)fiber is one of the most widely used synthetic fibers.It has such excellent properties as low density,high strength,chemical resistance and thermal resistance,and PP fiber has also rich raw material resource (propylene),good processability and lower cost and has been widely used in industrial textiles,clothings and decoration materials.However,its application is somewhat limited due to nonpolar molecular which causes low surface free energy and surface tension of PP fiber.The main defects of PP fiber are poor hydrophilicity,dyeing and compatibility with other polar polymers and inorganic fillers.In this paper,the blend-adhesion direct spinning and melt-spinning method was initially employed to produce the composite fibers.The results show that the dispersion of ultrafine CaCO₃ particles in polymer matrix and composite fiber mechanical properties were greatly improved.Three patents concerning with the issue have been applied(Application number:200810200443.X, 200810200444.4 and 200810200442.5).Meanwhile,as a comparison,the ultrafine CaCO₃/PP composite fibers were also prepared by normal melt-spinning method.The dispersion of ultrafine particles and structure and properties of PP fibers were investigated by mechanical property test,static and dynamic contact angle tests,SEM,FTIR,WAXD and DSC.The main works and conclusions were listed as following:1.Contact angle tests showed that the hydrophilicity of PP fibers was greatly improved by adding of ultrafme CaCO₃ particles.The contact angle was decreased from 110.4°to 25.8°.FTIR indicated that the improvement of hydrophilicity of the composite fibers was mainly due to the increase of polar groups on composite fiber surface.And the polar component was increased from 0.48mJ/m² to 49.79mJ/m²,which led to the increase of surface energy, adhesion work and surface polarity of composite fibers.Dynamic contact angle test showed the obvious hysteresis of contact angle,and the sharp decrease of receding contact angle were attributed to the increased surface roughness and inhomogeneity on composite fiber surface.2.The crystallization characteristic was investigated by means of WAXD and DSC.It was found that ultrafine particles served as a heterogeneous nucleation agent and accelerated the crystallization of PP fibers.And a littleβ-crystal could be found in the composite fibers.In addition,the crystal size in the composite fiber system was reduced.3.By using ultra-high speed mixer,the proper content of stearic acid was found 1.8wt%and a fine dispersion of ultrafme particles in PP matrix and consequently high surface activity could be achieved.FTIR analysis revealed that some new group fromed between ultrafme CaCO₃ and surface treatment agent.4.The ultrafme CaCO₃ was uniformly dispersed in composite fibers prepared by the blend-adhesion and direct melt-spinning method.SEM pictures indicated that a quite uniform dispersion of the ultrafine particles was achieved throughout PP matrix at low CaCO₃ content.And the mechanical properties were significantly enhanced with the tensile strength of 6.12cN/dtex (increased by 24.1%)and the unevenness of only 0.5%at 6wt%ultrafine CaCO₃ content.However,the tensile strength of composite fibers by blending method was only increased by 16.3%and the unevenness reached 18.5%. Moreover,the relatively poor dispersion of ultrafine CaCO₃ in the PP matrix was observed.