Poly (Ethylene Terephthalate) Having Higher Rigidity And Improved Toughened With Well Processability

Poly(ethylene terephthalate)(PET) is widely used in the fields of the fiber, film and soft drink bottle because of its excellent electrical insulating, resisting heat and chemical resistance properties. With the development of PET manufacturing technique, PET output has been increasing largely. In order to exploit the new applied fields and increase PET value, PET has been used as engineering plastic which is a hot research topic both at home and abroad.In order to use PET as the engineering plastic, two scientific and technical topics must be settled. First, the toughness of PET must be improved and its rigidity(tensile yield stress, TYS; flexural modulus, FM) must be preserved or decreased little. Second, to accelerate crystalline growth velocity and decrease cool crystalline temperature (Tcc), the product can be confectioned at low die temperature. Of course, it is better that the two topics can be settled at the same time, which is hot research topic at home and abroad.At home and abroad, the research works about PET have gotten some results, but there are still some scientific and technical difficult problems needed to be settled. Such as, when elastomers are used to toughen PET, toughness of the blends can be improved highly but its rigidity decreases severely; the methods that nucleators are added in PET blends can accelerate the crystalline growth velocity and achieve the technical request at low die temperature(70°C), but the toughness of PET is decreased.In order to get high toughen and rigidity property of PET blends at low die temperature, the structure characters of the excellent total performance PET were designed: the PET was continuous phase and the elastomer and well- crystallization polymer were disperse phase which chained with the continuous phase by the chemical bonds, and the well-crystalline polymer chained with the PET like iron hinges, the elastomer and the well-crystalline polymer were able to change the crystalline behaviors of PET. Based on the design approach mentioned above, a series of the titletoughening modified PET engineering plastics were prepared by thermal mechanical blending of the PET with the multifunctional master batch(MFMB) in different ratio. The MFMBs were synthesized in a low viscosity reaction system by grafting copolymerization and reactive blending technique starting from HDPE and butadiene-styrene elastomer as the toughening agent through chemical bond conjunction derived from a monomer containing an epoxy group in the presence of the benzoyl peroxide as the initiator. The chemical structures, crystalline morphology, and crystallization behaviors of the MFMBs and PET/ MFMB were characterized by IR, PLM, DTA analytical techniques and instruments etc. The results could be summarized as follows:1. In the preparation of MFMBs, the apparent conversion of monomer(Ta) was in the range of 26.4%~44.3%, which indicated that good compatibility in the MFMB existed between HDPE and elastomer, so did between MFMB and PET. when they were blended, the viscosity of the toughened PET was increased, so MFMB was a compound multifunctional master batch having good compatibility and toughness.2. the differences of MFR of the EN-SBMB, PET/EN-MFMB and PET/EN-SBMB indicated that the compatibility of the HDPE and elastomer in EN-MFMB was well, so did EN-MFMB and PET, and the viscosity of PET was increased by EN-MFMB.3. Crystallization of HDPE in the EN-SBMB, EN-MFMB and EN2-MFMB were nucleated hetero-generously.4. The cool crystalline temperature of PET in different PET/EN-MFMBs was lower than the pristine PET's, and the hot crystalline onset temperature of PET in different PET/EN-MFMBs was lower than the pristine PET's too. and the crystalline velocity of toughened PET was more rapid than that of pristine PET.5. Crystallization of PET in the PET/EN-MFMB was nucleated hetero-generously. With the EN-MFMB content in PET/EN-MFMB increasing, PETs' the crystallization nucleated hetero-generous was more obviously.6. The molt temperature (Tm) of HDPE in the PET/EN2-MFMBs was lower than Tm of the pristine HDPE and EN2-MFMB, the crystalline exothermic peak of HDPE in the PET/EN2-MFMBs was disperser than the pristine HDPE and EN2-MFMB's, asindicated that HDPE and PET were chained by the chemical bond and irregular HDPE crystals chained with PET.7. The high-performance modified PET could be obtained, whose toughness was largely increased, and rigidity (TYS, FM) was remained at the same time. The PET/EN2-MFMB with 24.2% EN2-MFMB, for example, when its NHS went up to 4.54-fold as that of the pristine PET, its TYS and FM were 103% and 99% of that of the pristine PET respectively.8. The overall mechanical properties product of PET/EN-MFMB could be prepared at about 60 die temperature.9. Under ordinary sheer flow condition, the PET and PET/EN-MFMB showed a pseudo-plastic feature. With EN2-MFMB content in PET/EN2-MFMB increasing, the apparent viscosity of melting PET/EN2-MFMB was increased and MFR was decresed.