Study On The Property Of Polyethylene Terephthalate Based Micro-nano Composites

The preparation of polymer based nanocomposites and its application has been considered as one of the most important research directions. The effect of the incorporation of micro-nano material on the properties of polymer matrix has attracted much attention in recent years. It can also direct the technology parameter during the processing.Polyethylene terephthalate (PET) is one of the most important polymer materials with high production and wide application. In present thesis, PET is adopted as matrix, and the other two typical micro-nano composites, zirconium phosphate loaded Ag+ and titanium organics, are adopted as additives to prepare PET based nanocomposites. The thermal properties, rheology behavior and crystallization behavior of both nanocomposites were studied by using DSC method, rheology analysis and isotherm non-isothermal crystallization kinetics. Particularly, for PET/ titanium organics composites, the orientation of titanium organics in PET matrix during processing has been investigated by using two-dimensional X-ray diffraction method. The structure and morphology of titanium organics separated from PET composites were also characterized through SEM, TEM, AFM,13C NMR and MALLDI-TOF-MS. Meanwhile, the possible formation mechanism of slice-like titanium organics during processing was also discussed here. For PET/zirconium phosphate loaded Ag+ composites, the spinning property was studied in a systematic way, and the mechanical properties as well as the anti-bacterial properties were examined. Finally, the supermolecular structure of the as-spun fibers and drawn fibers has also been studied in detail. The major results obtained are as follows:1. It is found the particles of zirconium phosphate disperse uniformly in PET matrix, with the size of about 1μm. The incorporation of zirconium phosphate induces a negligible effect on the melting temperature, the degradation temperature as well as the crystal form of PET matrix, while elevates the crystallization ability of PET matrix. The rheology properties of composites have been discussed by using dynamic rheometer analysis. The results show that the complex viscosity of composites is lower than that of pure PET. It is possibly related with the decrease of the macromolecular chain entanglements caused by the addition of zirconium phosphate.2. The in-situ formed titanium organics are dispersed uniformly in PET matrix in the form of slice-like, with the length, width and thickness of about 500nm,500nm and 120nm, respectively. The incorporation of titanium organics has little influence on the molecular weight and molecular weight distribution and the the melting temperature and the crystallization behavior of PET composites has little change compared with PET matrix. From the WAXD patterns, it is indicated that PET composite exhibits new diffraction peaks between 2θ=8°-12°, suggesting that the in-situ formed titanium organics have unique crystalline structure, which are different from the crystalline structure of TiO2 reported. However, there is an interesting phenomenon of rheology properties of PET/ titanium organics composites. The complex viscosity of composites is higher than that of pure PET at low shear rate (100S-1), while the complex viscosity of composites is lower than that of pure PET at high shear rate. This phenomenon is possibly related to the orientation of titanium organics. The orientation of titanium organics in PET resin, as-spun film and drawn film is studied in detail by two-dimensional X-ray diffraction method, and the results show that the slice-like titanium organics are leveled off in PET matrix and the crystalline structure of the titanium organics may be monoclinic. Moreover, it is found that the in-situ formed slice-like titanium organics are the reaction product of the titanium compound precursor with PTA and EG monomer which was characterized by FTIR,13C NMR and MALLDI-TOF-MS spectrum.3. The non-isothermal crystallization kinetics of PET based composites were investigated through DSC method. The non-isothermal crystallization data was analyzed by Ozawa, Jeziorny and Mo method, respectively. It is found that both the Jeziorny method and Mo method can describe the non-isothermal crystallization process of these two kinds of composites availably. Comparatively, the Ozawa method can not describe the PET/ zirconium phosphate composites quite well, while can describe the PET/ titanium organics composites. Anyway, the results indicate that the incorporation of both the titanium organics and zirconium phosphate could promote the crystallization rate of PET matrix.4. The spinning technology of PET/ zirconium phosphate composites was discussed. It is shown that the spinning ability of composites is good and continuous in the temperature range of 280～290℃, with the winding speed of 800m/min, 1000m/min and 1200m/min. The degree of macromolecule orientation of fibers was tested by using sound velocimeter instrument and the results show that the higher is the winding speed, the more orientation along drawn direction. Meanwhile, the incorporation of zirconium phosphate induces negligible effect on the orientation of PET composites. In addition, the stress at break of PET composites is decreased first followed by increasing again with increasing the content of zirconium phosphate, which is possibly related with the existence of the cracks and voids generated in PET matrix caused by addition of zirconium phosphate, leading to the decrease of the mechanical properties. Also, the results based on the preliminary bacterial test indicate that the PET/ zirconium phosphate composites fibers have good anti-bacterial ability, with anti-bacterial rate of about 90%.5. The effect of drawing on the crystallization and orientation during the fiber processing has been studied by using DSC, FTIR, WAXD and two-dimensional X-ray scattering methods. The DSC results show that there are two melting peaks existed in drawn fibers, while for as-spun fibers there is only one melting peak. Meanwhile, the glass transition and cold crystallization peak of drawn fibers disappear. It is suggested that the folding patterns of chain segments were change after drawing processing. The content of gauche conformation and trans-conformation of fibers was calculated and it is found that the content does not change obviously. From WAXD results we can see that the diffraction peaks corresponding to (110), (100), (111) crystal planes can not exhibit in as-spun fibers, whereas these peaks exhibit in drawn fibers. According to Scherrer equation, the crystal sizes were calculated and it is shown that the crystal sizes of drawn are larger. Finally, the correlation distance and the gyration radius of fibers were calculated in the aid of two-dimensional X-ray scattering method. It is indicated that correlation distance a01of drawn fibers is decreased, wheraes a02 is increased. However, the gyration radius of drawn fibers is larger than that of as-spun fibers, suggesting that the macromolecular chains of drawn fibers were stretched more dramatically.