| The melting blending technology is one of the most important methods to prepare new kinds of polymer composites. Compared with the synthesis of new polymer, this method has advantages in several aspects, such as short production cycle, strong operability and convenience. Meanwhile, the blends of different polymers always have some excellent properties that single polymers do not possess.In this paper, the blends of poly (ethylene terephthalate) (PET) and polycarbonate (PC) were prepared by co-rotating twin screw extruder. The properties of these blends were studied, in order to find a way to prepare high performance PET/PC alloys.The compatibility of PET/PC blends has been studied using differential scanning calorimetry (DSC), scanning electronic microscope (SEM) and other testers. Without compatibilizers, the two glass transition temperatures of PET and PC shifted closer to each other with increasing content of PET, which meant that this blend was partially miscible. SEM photographs showed that, in the PET/PC (70/30) blend, PC phase dispersed very well in PET matrix.The DSC curves showed that the lower temperature crystallization rate of PET in the PET/PC blends was improved; however, the high temperature crystallization rate was slower than pure PET and changed slightly with the content of PC. On the other hand, the crystallinity degree (Xc) of PET in the blends was decreased with addition of PC. The study of melting flow rate (MFR) and equilibrium torque showed that the melt flowability of PET/PC blends was improved by the addition of PET and achieved the optimum effect when PET content was 65%~70%.The addition of different compatibilizers reduced the tensile and flexural properties in some extent; however, the impact strength was increased greatly. By adding only 3% of ethylene-butyl acrylate-glycidyl methacrylate copolymer (PTW) or 3% of ethylene-ethyl acrylate copolymer (EEA) into PET/PC (70/30), the impact strength increased from 5.60 KJ/m2 to 9.86 KJ/m2 and 8.40 KJ/m2 respectively, but the tensile strength and flexural strength decreased by only 5~10%.The toughening modification of PET/PC blends was studied using different kinds of elastomers such as PTW and EEA. The results showed that the impact property of PET/PC blends was improved significantly by the addition of PTW. With 20% of PTW, the impact strength of the PET/PC blend increased from 5.60 KJ/m2 to 98.2 KJ/m2. The toughening effect of EEA was not perfect as PTW. When adding 20% of EEA, the impact strength of the blends increased from 5.60 KJ/m2 to 21.03 KJ/m2. On the other hand, PTW decreased the melt flowing rate of PET/PC blends significantly, while the influence of EEA was much more slightly. The distribution of PC in the polymer matrix could be furtherly improved by addition of PTW, which worked as compatibilizer.Poly(butylene terephthalate) (PBT) has similar chemical structure with PET, so the blends of PBT and PET exhibit an excellent compatibility. Furthermore, the impact strength, processing flowability and crystallization capacity of PBT are better than that of PET. As a result, the blends of PET/PBT have been studied by many researchers.In this paper, a small amount of PBT was introduced into EEA as composite flexibilizer (the total amount of EEA/PBT was kept as 20%). The results showed that the impact strength of PET/PC blends was further improved by EEA/PBT composite flexibilizer. At the same time, the tensile and flexural strength were kept in certain extant, the surface appearance of these blends was also improved. The results showed that, the PET/PC blends modified with 15%EEA/5%PBT composite flexibilizer showed the optimum impact strength, which was about 90.15 KJ/m2. On the other hand, SEM photographs showed that there was no separated phase after the addition of PBT.The results showed that, the blends prepared by PET/PC (70/30) with 20% PTW or 20% EEA/PBT composite flexibilizer (EEA/PBT=15%/5%) achieved the optimum comprehensive properties. |
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