Study On The Blends And In-situ Microfiber Composites Of PET/PC

Polymer blending has been widely accepted for improving mechanical properties of materials, and it is an effective way to obtain materials with specific properties. In recent years, in-situ microfiber-reinforced materials have attracted considerable attentions. The materials are usually in-situ formed during processing. In this paper, first of all, the basic properties of PET/PC blending, for example the blends’ morphology, crystallization property, rheological behavior and thermal stability properties, were studied. Moreover, PET/PC in situ microfiber composites were produced through "Melt extrusion-Hot drawing-Quenching" in the screw extruder. And the microfibers morphology, microfibers diameter distribution and mechanical properties were also investigated. The major findings are as follows:(1) FTIR, SEM, DSC were used to research on the compatibility of PET/PC blending. Through SEM, the compatibility of PET/PC blending was not well. The FTIR results showed that there was the transesterification reaction between PET and PC. And the transesterification reaction improved the compatibility of the two-phase.(2) Cold crystallization and melt crystallization of PET/PC blending were studied via DSC. The results showed that the cold crystallization temperature gradually increased, the melting crystallization temperature decreased with PC content increasing. Crystallinity and crystal morphology were studied via WAXD and POM methods, the results indicated PC could restrain the crystallization of PET.(3) The pure PET, PC static viscosity increased with the shear rate increasing, and showed shear-thinning phenomenon through Advanced rotary rheometer. At the same time, PET/PC blending dynamic rheological viscosity showed a downward trend with the shear frequency increasing. Under the same blending ratio and shear frequency, the viscosities of blending samples showed a noticeable drop with the temperature increasing. Under the same temperature and shear frequency, the viscosities of the blends decreased with the PET component increasing, which indicated that PET can improve the PC processing property.(4) The thermal decomposition temperature of the blends slightly increased with PC content increasing. But because of the presence of transesterification reaction, the thermal decomposition onset temperatures of blends were lower than the two pure components.(5) PET/PC in-situ microfiber blending fibers were produced through "Melt extrusion-Hot drawing-Quenching" on a single screw extruder. The influences of PET mass content (Cm) on the morphology and diameter distribution of PET microfibers were studied. The results indicated that the number of microfibers presented the maximum and the distribution of microfibers was narrowest when PETs Cm was 30%. The diameter of microfibers decreased with drawing ratio increasing. Mechanical performance test results illustrated that:tensile strength of PET/PC in situ microfiber blending fibers increased firstly and then decreased at PET’s Cm 30%; with the drawing ratio increasing, breaking strength of PET/PC in situ microfiber blending fibers gradually increased.(6) The morphology evolution of PET/PC blend system was studied through SEM in the twin-screw extruder. It can be found that the dispersed phase PET changed little particles from larger ones, finally, formed the sheet shape. In addition, PET/PC in-situ microfiber blending films were produced through "Melt extrusion-Hot drawing-Quenching" in a twin-screw extruder. Moreover, the influences of drawing speeding on the morphology and diameter distribution of PET microfibers were investigated.