The Study On PBT/RMFMB/rPET Blends

Poly(butylene terephathalate)(PBT) has been an important one of the five engineering thermoplastics, used widely in auto and so on. However, it has some weaknesses which have prevented its using in large-scale applications, such as the low notched impact strength and the bad rigidity under high temperature. In order to enlarge the using ranges and satisfy the more requirements for performance, it is necessary to improve the toughness and rigidity of PBT at the same time. A lot of research works have been done at home and abroad, such as toughened with elastomers, blending with thermoplastic resin, reinforced with glass and so on. Toughened with elastomers, toughness can be greatly improved, but the stiffness (tensile yield stress, flexural modulus of elasticity) was significantly lower. Blending with Polyethylene terephthalate (PET), nylon(PA) and other thermoplastic resins, the price is too high. Using recycled poly(ethylene terephthalate) as the restronghten material not only can prepare composites with high toughness and rigidity, but also utilize wastes, which has very important economic, social and research value.For developing the PET with the toughness large scale enhacement but the rigidith not to reduce or little improvement, a research idea was put forward to prepare a sort of reactive multifunctional master batch (RMFMB) and optimization of reactive blending process. The RMFMB could reactive compatibilizated and toughnessed to PBT and rPET, and restrain the lower composite’s rigidity. RMFMB, rPET and PBT have chemical bonds through the chemical reaction between the epoxy functional group in RMFMB and the bottom -OH,-COOH of PBT and rPET chains, could interface strength between PBT and rPET. Toughening component can toughened PBT obviously. At the same time, reveting-hinge function of minicrystal in RMFMB to PBT and rPET could restrain the PBT’s rigidity decreasing. Ideal morphology could obtain by optimization of reactive blenging process.Based on the above design idea, the RMFMB was synthesized by the mechanism and technique of "polymer-bridge conjunction and dynamic vulcanization", usingHDPE, ethylene-propylene elastomer, butadiene-styrene elastomer, a reactive containing an epoxy group and an assistant as main material in this work. And then, the toughened PBT(PBT/RMFMB/rPET) was prepared by thermo-mechanical blending with different several types of feeding ways, and the toughness was improved obviously and rigidity was maintained. Subsequently, we studied the chemical structure, melt flow rate of RMFMB and the chemical structure, fractured morphology, mechanical properties, non-isothermal crystalline behavior and morphology and melt flow rate of PBT/RMFMB/rPET composites. The main results and conclusions were summarized as follows:(1) The expoxy functional group of RMFMB-2 preparated by the low viscosity system was singnificantly higher than that of RMFMB-1 preparated melted.(2) RMFMB had certain mobility. In particular, the mobility of RMFMB-2(O) was the best.(3) RMFMB-2(O), rPET and PBT have chemical bonds through the chemical reaction between the epoxy functional group in RMFMB-2(O) and the bottom-OH,-COOH of PBT and rPET chains.(4) The blending processes have an important effect on the structure and mechanical properties of BT/RMFMB-2(O)/rPET. When the content of RMFMB-2(O) was 15wt%, PBT-70%RMFMB-2(O)/rPET/30%RMFMB-2(O) composites had the best overall mechanical properties. The NIIS got to 2.91 times that of pure PBT, the TYS strength and FM were maintained 98% and 104% respectively that of pure PBT.(5) The NIIS of PBT-70%RMFMB-2(O)/rPET/30%RMFMB-2(O) increased with the content of RMFMB-2(O) increasing, the TYS and FM decreased.When the content of RMFMB-2(O) was 15wt%, PBT/RMFMB-2(O)/rPEThad the best overall mechanical properties. The NIIS got to 3.25 times that of pure PBT, the TYS strength and FM were maintained 97% and 101% respectively that of pure PBT. The MFR of PBT/RMFMB-2(O)/rPET decreased gradually. The crystallization morphology of PBT in PBT/RMFMB-2(O)/rPET composites was refined gradually.(6) The TYS of PBT-70%RMFMB-2(O)/rPET/30%RMFMB-2(O) had no obvious viration with the content of rPET increasing, was maintained 96% that of pure PBT; the FM decreased from 106%(rPET=8.5wt%) to 99%(rPET=34.0wt%) that of pure PBT; the NIIS increased from 2.57 times(rPET=8.5w/%) to 2.96 times(rPET=34.0wtt%) that of pure PBT. The MFR of PBT/RMFMB-2(O)/rPET also decreased gradually with the content of rPET increasing.(7) The melt temperature of PBT, rPET and HDPE in PBT/RMFMB-2(O)/rPET for the first heating DSC curve is lower slightly than the pure PBT and rPET. And the melt temperature of HDPE in PBT/RMFMB-2(O)/rPET is lower obviously than the pure HDPE. There were two melting peaks. The big was PBT’s, was lower 1.1-3.6℃than that of pure PBT. The small was rPET’s, was lower 39.6-40.6℃than that of pure rPET.(8) There was only one cool crystalline peak in PBT/RMFMB-2(O)/rPET. Compared to PBT, the cool crystalline temperature of PBT increased slightly, but decreased obviously compared to rPET. And the deceasing and increasing extent changed with the different feeding ways. There was only one heating crystalline temperature, and it was between the PBT’s and rPET’s. The heating crystalline peak of HDPE is lower, appeared after the crystalline process of PBT and rPET.