The Study On Ultrafine Powered SiO₂ Dispersion Cotrol Methods In PET

Adding antiblock agent in PET used for film, and improving some basic characteristics of PET have attracted much attention. However, the homogeneous dispersion of ultrafine particles in polymer matrix is very difficult because they have a strong tendency to agglomerate and have poor compatibility with polymer. It is difficult to synthetic ideal composite, especially the dispersion of ultrafine powder in polymer is difficult to control. In this paper, considering of this difficulty the experimentals were designed and discussed.The hydrolysis process of silane coupling agent KH570 was studied in this paper. The factors which affect the hydrolysis process were changed to obtain the best conditions, the hydrolysis degree was monitored on line by the method of conductivity. Finally experimental results show that the best hydrolysis conditions were : KH570:H20:alcohol=1:1:4(by weight); pH=4～6; time for hydrolysis was 30min.The ultrafine SiO2 powder was modified with KH570 under optimized conditions followed by characterization using TG and IR. The results indicate that chemical reaction occurred between KH570 and SiO2 on particle surface; when KH570: SiO2 (by weight) =1:5, the modification effect was optimum. Dispersing experiments were carried out by means of mechanical stirring and ultrasonic treatment, and the dispersion was analyzed by deposition and spectrophotometer observations. The deposition height after 18h and transmittance manifested that the dispersion of modified SiO2 was superior to non-modified SiO2 no matter nano particles or micron-sized particles and was proved mechanical stirring to be superior to ultrasonic treatment.The PET/ SiO2 composite was made by in-situ polymerization. The SiO2 dispersion was characterized by SEM. The results show that dispersion of modified SiO2 in PET was improved than original SiO2. but reached nanometer dispersion, dispersible uniformity was not perfect. In the end, testing the intrinsic viscosity and thermodynamics property of PET, the results manifested that as the SiO2 particle loads increasing, Tg and intrinsic viscosity of PET was decreased obviously, Tm was increased first and then was decreased.