Study On The PET Fiber Modified By Silicon Compound

Polyethylene terephthalate （PET） is a kind widely-use synthetic polymer because of its excellent physical、chemical and mechanical property. The strength of PET fiber is great, so it has the defect of pilling. The development trend of functional and differential fiber, such as anti-pilling fiber. The anti-pilling fiber can be used as high quality textiles and thick textiles.The research on the modified PET was made in this thesis. A series of modified polyethylene terephthalate was got through melt polycondensation by diphenylsilanediol and different molecular weight poly（ethylene glycol）（PEG） as comonomers. The structure and properties of samples were characterized by means of differential scanning calorimetry （DSC）, thermalgravity analysis（TGA）, ¹HNMR spectroscopy, Fourier transform infra-red spectroscopy （FTIR） and scanning electronic microscope（SEM）. The results were as follows:1. The modified PET was prepared successfully through normal crafts and the comonomers had no effect on the polycondensation.2. The glass transition temperature （Tg） of samples reduced from PET-1 to PET-7. The melt point of all the modified PET were lower than pure PET. Analysis of the DSC data was carried out based on the several models. It was found that the Jeziorny model provided a satisfactorily good fit to the experimental data for these polyesters. The Avrami exponent ranged from 2.5 to 4.14. The Kc value of each sample increased as the cooling rate increased. It illuminated that the greater cooling rate, the faster crystallization rate. the results were consistent with the t_1/2 value. The results of TGA showed the comonomers had rarely effect on the thermal stability of PET.3. The orientation degree of PET-1 was the highest, while PET-5 was the lowest. The orientation index decreased as the diphenylsilanediol content increased. The rupture strength of all samples after hydrolysis decreased, but the rupture elongation ratio of samples after hydrolysis was bigger than the no hydrolysis samples. The PEG as comonomer could accelerate hydrolyzing of fiber.4. A quantitative method for characterising polyester end-groups was described. The trichloroacetyl isocyanate （TAI） reacted rapidly and quantitatively with both carboxyl and hydroxyl chain ends to form derivatives that can be readily determined by ¹HNMR spectroscopy. The TAI capped end-groups gave rise to characteristic imidic NH resonances in a normally clear region of the ¹HNMR spectrum [δ:10.32 for C（O）-O-C（O）-NH from C（O）OH,δ:8.54 for O-C（O）-NH from OH]. The end-groups content change was determinated, which reflected the hydrolysis degree for estimating the anti-pilling property of samples indirectly. 5. The absorbable bands of main function groups was confirmed by FTIR. Comparing the position、shapes and strength of absorbable bands of main groups before and after hydrolysis, there were little difference in theν（OH） band shapes between them. All peaks were broad and the peak transferred into lower wavenumbers. There was a dramatic change in the shape, number and intensity of the bands in theν（C-H） region during the hydrolysis process. The change ofν（C=O） was more complicated. The main peak transferred into higher wavenumbers slightly, and the peak shapes were broader after hydrolyzing. Theω（CH₂） band augmented observably of samples added PEG. It indicated that the hydrolysis degree was more obviously than the samples added diphenylsilanediol only.6. From the surface morphology by SEM, the hydrolysis degree of the samples added diphenylsilanediol and PEG at the same time was the greatest.