High Performance PET And PC/PET Alloy

Poly(ethylene terephthalate)(PET)is one of the general engineering plastics with wide application.However,the molecular chain of PET contains a large amount of ester groups which are easy to undergo thermal degradation and hydrolysis reactions during processing.These side reactions lead to the breakage of molecular chains and the decrease in the molecular weight and the mechanical properties.At the same time,the crystallization rate of PET is slow,especially for chain-extended PET,which restricts the application of PET.The addition of a chain extender and a nucleating agent towards PET is carried out to solve the problem above.At the foundation of chain-extended PET,PET is further blended with polycarbonate(PC)in order to produce alloy combined good properties of PET and PC.The addition of a transesterification catalyst,a chain extender and an impact modifier towards PC/PET alloy to accomplish this target.The effort will expand the application of PET and PC/PET alloy.In this paper,poly(phenyl methylene isocyanate)(PMDI)was used as the chain extender and Surlyn~?as the nucleating agent.Crystallization and chain extension modification of PET was carried out by combining PMDI with Surlyn.The effect of PMDI and Surlyn on the modification of PET was investigated by differential scanning calorimetry and scanning electron microscopy,etc.Cobalt acetylacetonate(Co(acac)2)was selected as the transesterification catalyst,PMDI as the chain extender and polyolefin elastomer(POE)as the impact modifier.The effect of Co(acac)2,PMDI and POE on the PC/PET alloy was investigated by the intrinsic viscosity test,dynamic mechanic analysis and the mechanical property test,etc.The experimental results show that all additives are effective.And PMDI increases the compatibility between Surlyn and PET,which improves the crystallization of Surlyn towards PET.The chain-extended PET with high crystallization rate was produced.When 1.4 wt%PMDI and 1.2 wt%Surlyn added,the half crystallization time of PET was decreased from1.34 min to 0.74 min and the intrinsic viscosity was increased from 0.60 dL/g to 1.12 dL/g.Adding PMDI also solves the degradation problem of PC/PET alloy during processing.PC/PET alloy with high melt flow rate and high impact strength was produced.When 0.05 wt%Co(acac)2,0.5 wt%PMDI and 7.5 wt%POE were added,the melt flow rate of PC/PET alloy was increased from 10 g/10min to 38 g/10min and the notched impact strength was increased from 82.8 J/m to 482.3 J/m.