Study On Preparation And Properties Of PET Antistatic Composites

For the properties of its high strength and rigidity, excellent thermal resistance and dimension stability, as well as the prominent chemical insulation, Poly(ethylene terephthalate) has an outstanding performance all round. So it's widely used in electrical and electronic parts, packaging materials and automotive components. PET is inherently an electrical insulator, exhibiting the surface resistivity of 10¹⁵ to 10¹⁶ΩThe static charge that easily builds up on such molded parts by contact or rubbing may cause an electrostatic discharge, which becomes a serious problem. There may be electrostatic damage to sensitive semiconductor devices and interference with circuit operation, especially in the electronic industry. The antistatic modification of PET is being attached importance to more and more in the industry.The antistatic mechanism, mechanical property, processing rheological property and morphology of the composites prepared by means of blending PET with three kinds of antistatic agents were investigated. It was indicated that the blends of PET with the addition of Tas 1125C and KS-I, showed a better antistatic property. The surface resistivity of the composites was reduced by 6-7 orders of magnitude containing antistatic substance of 3wt% content. The PET antistatic composites showed a better antistatic property with the surface resistivity dropping gradually before 20 days but kept constant after 30 days and decreasing with the temperature increasing. The effect of the moisture of atmosphere on the resistance of PET sample was remarkable, and the relationship of water content in the unit surface area and the change of the surface resistivity was approximately linear. In addition, the factors such as washing for antistatic composites and dispersion of antistatic agents, had also certain effect on the antistatic property. The mechanical properties of the composites had a little change compared to the pure PET when the addition of Tas 1125C and KS-I. The processing rheological property of PET/Tas 1125C blends was better than other two kinds of antistatic agents KS-I and HBS-204P.Tetrapod-shaped ZnO whisker(ZnOw) was used as the conductive filler to prepare PET/ZnOw composites by extruding mixture. The antistatic property, conductive mechanism, mechanical property, SEM microstructure, crystallization and melting property, thermal stability and processing rheological property were investigated. The results indicated that the silane coupling agent was grafted onto the surface of ZnOw and interacted well with PET matrix. ZnOw plays a significant role in reducing the resitivity of polymer composites and is an effective antistatic agent for resin materials. The conductive mechanism can be classified into runnel effect, discharging effect at the pinpoint and conductive network. The simple formula of critical volume fraction( v_c) for ZnOw forming conductive network is proposed, based on the actual processing conduction. Comparison of the theory value to the experimental data showed a close agreement. The dielectric constant and loss of PET/ZnOw composites increased with the increasing of the content of the whiskers and dropped with the increasing frequency. With the increasing load of ZnOw, the mechanical properties of all materials increased initiately and then decreased. In comparison with pure PET, the tensile strength, flexural strength and impact strength, increased 14.3%, 18% and 110% when the addition of ZnOw is 12%, 10% and 8% respectively. It can be seen from the SEM of impact fracture that the tetrapod-shaped needles of the broken ZnOw consumed the impact energy, so increasing the impact strength of PET/ZnOw sharply. ZnOw particle behaves as the nucleating agent. Compared with pure PET, the crystallization rate and crystallinity of the PET/ZnOw increase, and the crystallite size decreases. The thermal stability of the composites is slightly enhanced by the addition of ZnOw. The maximum torque, plasticizing time and balance torque increased obviously comparing with pure PET resin when increasing the load of ZnOw, so the flow resistance increased gradually.