Study On Toughening Modification Of The PET As The Engineering Plastic

Poly (ethylene terephthalate) (PET) is the thermoplastic that has low cost, high performance. However, the most serious shortcoming of this material is its very low impact strength. The research on the high-performance, the high-added value PET used as the engineering plastic has the important social,the economic significance and the academic value, which solves the contradiction between PET production capacity growth and the product demand growth in our country and also disposes of the more and more PET waste. In this paper we studied that PET/rPET was modified with chain extenders and find the best chain extender by contrasting and analyzing the intrinsic viscosity of PET/rPET and the crystallization performance that was tested by DSC; then we investigated that PET was toughened with polyester elastomer and the different systems' mechanical properties, thermal properties, dynamic viscoelasticity and microcosmic performance. The key findings of this paper are as follows:First, the impact on the intrinsic viscosity of drying time on PET/rPET was studied. Through the intrinsic viscosity of the PET/rPET that was tested by Ubbelohde viscometer we can see, the blends in the mixing process had the smallest degree of water degradation when the specimen at 170℃dry 8 hours. And the bicyclic anhydride types of chemical chain extenders PMDA and A900 in the PET/rPET modification of the extended chain of increased viscosity was examined. We studied the chain-extension effect of PET/rPET with different contents of PMDA and A900 by measuring the viscosity, moreover, we studied the regularity for change of crystalline properties by DSC when PET/rPET was extendered. The research shows that, the effect of the chain extender (PMDA) on polyester is better than A900. The intrinsic viscosity of PET/rPET is respectively 0.93815dL/g and 0.79587 dL/g when the percentage of PMDA to reach 0.6wt.%, which reached the minimum requirement of PET/rPET, used engineering plastics. We found that the intrinsic viscosity of polyester didn't increase with the content of chain extenders improving, and when the intrinsic viscosity of PET/rPET exceeds the maximum value, it would drop if we continue to add chain extenders. The intrinsic viscosity of PET/rPET was inversely proportional to its crystalline properties by DSC.Second, using elastomers ((1), E-MA-GMA; (2), POE-g-MA; (3), SEBS-g-MA; (4), PTW) to toughening modification of PET. The experimental results show that the best toughening modification of the PET is the second elastomer, when its dosage is 6 wt.%, PETimpact strength increased about 75.8% than pure polyester PET, its tensile elongation at break rate increased by 58.4%; when its using reached 12 wt.%; the impact strength increased about 184% and its elongation at break increase of 147.8%, demonstrated high toughness. We could find this trend in tests result in the DMA and SEM tests.