Study On The Preparation And Properties Of PTT/PE Blends And In-situ Microfiber Composites

As a new type of polyester, poly（trimethylene terephthalate）（PTT） was first used in fiber industry due to its excellent performances in fiber application. It overcomes the weakness of rigid PET fiber and flexible PBT fiber and has advantages of both polyester and polyamide fibers. The physical property of PTT is similar to PET and the processing property is better than PBT, so it is a promising engineering plastic. But as a kind of novel material which has fine properties, the further investigation of PTT in application of plastic field.Inspired by the in-situ microfiber composite which is a hot research point recently, PTT/PE in-situ microfiber composite is prepared from the view of "in-situ microfiber reinforced material". By controlling the process conditions, PTT existed as dispersed phase in the form of microfiber in the polyethylene （PE） continuous phase. PTT was the skeleton frame of PE, thus it increased the tensile strength and the notched impact strength of PE greatly and widened the application range.Because PTT and PE are not miscible in thermodynamics, the size of the domains of PTT dispersed phase is big and not uniform in the simple mechanical blending. And the mechanical performance of the composite is severely affected. PE-g-MAH was used in this study as compatibilizer to improve the compatibility of PTT and PE. The influence of the amount of compatibilizer, the content of PTT and the melt stretch speed on the morphology of PTT/PE system has been studied. The result showed that the optimum content of compatibilizer was 4% of the total weight of PTT/PE composite.The TGA analysis showed that the blends had a good thermal stability in large-scale temperature（0³90°C）.The crystal morphologies of the blends were also investigated by isothermal crystallization using Polarizing Microscope with hot stage （POM）. It can be found that the dimension of spherulites increased with time extended in the POM observations. Compared among different crystallization temperatures , the largest dimension of spherulites was observed at 190°C for PTT/PE （30/ 70）.The DSC result illustrated that the value of the temperature corresponding to the exothermic peak decreased while the half- time of crystallization (t_1/2) increased with the cooling rate increasing. The kinetic constant of crystallization （Zc） decreased with the cooling rate increasing. It was also found that the crystallization rate of the blends decreased with the cooling rate increasing.The fiber and the molding sample surface were saturated in xylene solution, the longitudinal morphology of the composites were observed by SEM. The results showed that the component PTT was indeed formed into micro-fibers. The tensile strength and the notched impact strength of the in-situ microfibrillar composites were tested. The results indicated that the mechanical properties of the in-situ microfibrillar composites were obviously higher than common PTT/PE blends.PTT/PE blend fibers were prepared in this paper. The test results showed that the rebound resilience was excellent. However, the two components are quite different in structure and the compatibility of PTT/PE is poor, thus the mechanical properties of the blend fibers were not very good and many of them need further investigation.