Preparation Of R-PET/ABS Composites And Their Crystallization Kinectics

PET is widely used in all aspects, because of its excellent mechanical properties. Its produced "white pollution" has seriously impacted on human survival environment, and caused the waste of resources. So how to recycle and utilize PET is a very valuable research topic. This paper prepared a kind of r-PET/ABS/SMA composite with SMA as compatibilizer and studied its structure and performance, based on the effects of extrusion times for r-PET performance. The basic contents and conclusions are as follows:(1) This paper studied the influence of extrusion times on r-PET performance by multiple melt-extrusion through twin-screw extruder. The characterization results of Ubbelohde viscometer, Vicat softening temperature tester and a melt flow rate instrument showed that viscosity average molecular weight, heat resistance and melt flow of r-PET totally decrease with the increase of extrusion times. The results of Haake torque rheometer show final torque stabilize at a value of 0.2N-m, it reflected the low melt viscosity. The reason for these phenomena is related to the decrease of the molecular weight which was caused by side reactions of r-PET processing, such as thermal degradation and hydrolysis. Experimental results showed viscosity average molecular weight and other r-PET performance tend to be stable after the melt-extruded four times, it illustrates processing conditions have little influence on the performance of r-PET at this time.(2) A series of r-PET/ABS composites with different component were prepared by melt-extrusion. The results of scanning electron microscope (SEM) proved the presence of obvious phase interface between ABS and r-PET, this indicated that the compatibility between ABS and r-PET was not ideal. By the mechanic test and processing performance, the Izod impact strength and melt viscosity has been improved by adding ABS, but the results showed a serious negative influence of tensile properties of r-PET. The results of differential scanning calorimetry (DSC) displayed that the crystallization process of r-PET has been promoted in the first heating process due to the heterogeneous nucleation effect of the SAN phase of ABS. However, in the second heating process after the annealing, the addition of the ABS into r-PET hindered the crystallization process of r-PET because of the intense exercise and the interaction between segments.(3) The method of preparation of r-PET/ABS/SMA composites with different SMA content was similar to that of r-PET/ABS composite and the Influence of the compatibilizer of SMA to structures and properties of these composites was discussed in this paper. The results of SEM showed that the addition of SMA greatly improved compatibility between r-PET and ABS, which made the regional dimensions of ABS phase being significantly reduced and dispersing more evenly. The mechanic test and processing properties displayed that the mechanical properties and melt viscosity of the r-PET/ABS composites were improved with the increase of content of SMA. However, when the content of SMA reached 10wt.%, the r-PET/ABS composites presented a co-continuous structure, the mechanical properties and melt viscosity began to decline. The first heating curve of DSC proved that the secondary crystallization of r-PET was more complete with the addition of SMA. During the second heating process after annealing, addition of SMA strengthened the obstacle of ABS to the crystallization process of r-PET.(4) The non-isothermal crystallization process of r-PET, r-PET/ABS and r-PET/ABS/SMA was studied By DSC. The results showed that the crystallization temperature of the three systems all decreased with the increasing of cooling rate, while the crystallization rate was opposite. In the same cooling rate, the crystallization starting temperature and crystallization rate of r-PET was the maximum, while r-PET/ABS/SMA was the minimum. What can be obtained at the same time is that the nucleation method has dependence on the cooling rate. The methods of crystal growth of r-PET exhibit a transition from multidimensional to low-dimensional as the cooling rate increasing.