Study On Toughening And Reinforcing Modification And Modified Mechanism Of Poly (Trimethylene Terephthalate) (PTT)

Poly (trimethylene terephthalate) (PTT) belongs to the thermoplastic aromatic polyester family which is industried recently. It has some advanced properties such as enhanced tensile flexural strength, thermal and barrier properties. Compared to aromatic polyester, its strength and rigidity is similar to PET and also has good process properties as PBT. Due to its advanced properties, PTT is considered as new and hopeness polyester material in 21 century, which is a competitor of application in engineering thermoplastic markets such as car, auto and electric equipment. PTT is a tough and ductile material in the unnotched state. The presence of sharp notches or curvature in the material leads to failure in a brittle manner. How to obtain higher tensile or yield strength as the impact strength of material increases has been an object hunted for by many polymer stuediers. In this work, toughening and reinforcing modification of PTT by blending with elastomers (POE-g-MA、EPDM-g-MA and SEBS-g-MA) and OMMT particles, polypropylene, respectively, and by blending with "core-shell" particles with a reactive compatibilizer diglycidyl ether of bisphenol-A (DGEBA) as well was investigated. The mechanical properties, microstructure and the relationship between them were also carefully studies. The toughening mechanism of "core-shell" particles was then proposed. The main works and conclusions were listed as following:(1) High impact strength of PTT composites material were prepared by blending with three different elastics (POE-g-MA、EPDM-g-MA and SEBS-g-MA). The mechanical properties of three composites material was investigated and compared. The result showed that PTT/POE-g-MA blend has lower balance torque and higher melt flow rate than PTT/EPDM-g-MA blend. The notched impact strength increased from 4KJ/m2 for pure PTT to 24KJ/m2 for PTT/POE-g-MA blend and 16.9KJ/m2 for PTT/EPDM-g-MA blend, respectively. However, the notched impact strength of PTT/SEBS-g-MA blend was not improved obviously. The surface of fracture morphology of SEBS-g-MA is smooth, which is brittle fracture. The Izod impact fracture morphology of the PTT/POE-g-MA showed that the characteristics of ductile fracture. According to Wu’s criterion, the critical interparticle distance of PTT/POE-g-MA blend is 0.798μm.(2) The addition of an organoclay to PTT/EPDM-g-MA blend led to ternary compounds came together as a means of balancing stiffness/strength versus toughness /ductility. Morphologies analysis showed that EPDM-g-MA particle dispersed in PTT matrix and the dispersed domain size (D) becomes large at lower clay content and then smaller at higher clay content. The clay platelets located inside the dispersed domains of EPDM-g-MA phase. The clay platelets do not act effectively as a barrier for the coalescence of the dispersed domains and led to the size of the dispersed domains of EPDM-g-MA became large. The complex viscosities blend incrased with the amount of the organoclay increasing, which are proposed as the reason for the dispersed domain size becomes smaller at higher clay contet. Mechanical tests showed that the EPDM-g-MA improved the toughness of PTT matrix, and the stiffness was obviously increased compared to PTT/EPDM-g-MA blend when added clay to blend, which indicated that the clay could improve the stiffness of blend.(3) An impact modifiers were prepared by melt blending POE-g-MA with different PP content. Mechanical proproties and morphology development of ternary blends were investigated with different impact modifiers content. The morphology analysis showed that through interfacial reaction, the maleinated POE encapsulate the PP domains and then dispersed in the PTT matrix. This means that the interfacial reaction between the hydroxyl-end group of PTT and maleic anhydride of POE induces the change of the formation of the domains composed of two dispersed phases. The lower interfacial reactivity is enough to obtain the reduction ofλPOE-g-MA/PP andλPOE-g-MA/PP is positive. The result of mechanical tests showed that when impact modifier content was up to 10wt%, brittle to ductile transition of the blends took place. The impact strength of PTT/E70P30 blend was lower than that of PTT/POE-g-MA blend.(4) Poly (trimethylene terephthalate)/polybutadiene grafted polymetyl methacrylate (PBA-g-PMMA, MB) blends were prepared b y melt processing with varying weight ratios of diglycidyl ether of bisphenol-A (DGEBA) epoxy resin as a reactive compatilizer. DMA result showed PTT was partially miscible with MB paricles in the presence of the compatibilizer. Fourier transform infrared (FTIR) and rheological measurements further identified the reactions between PTT and DGEBA epoxy resin. Mecchanical tests showed the impact and tensile properties of PTT blends are improved by the introduction of DGEBA epoxy resion to the blends.(5) The toughening mechanisms of PTT/MB blends with DGEBA were proposed. The results showed that shear yielding of PTT matrix and cavitation of rubber particles were the major toughening mechanisms.