Nucleating Agent Crystallization Behavior Of Pet And Glass Fiber Reinforced Pet Engineering Plastics

In this article, the crystallization behaviors of pure polyethylene terephthalate (PET) and PET/nucleating agents are studied by DSC technique and HAAKE Rehometer. The morphology and appearance of PET/nucleating agents is investigated by Polarizing Optical Microscope(POM) and Scanning Electronic Microscope(SEM). After that proper nucleating agents were selected from the three category material: low molecule nucleating agent,polymeric nucleating agent and compound nucleating agent, on the basis of above study, high performance glass fiber reinforced PET engineering plastics was prepared through twin-screw extruder equipment.According to DSC and non-isothermal crystallization kinetic analysis, with the increase of PET viscosity, the onset crystallization temperature shifted to the low temperature zone, half-crystallization time shortened and the crystallization rate slowed down. As the cooling rate increased, the crystallization becomes difficult. The presentation of nucleating agents has greatly improved the crystallization behavior, among the three types nucleating agents, polymeric nucleating agent has better effect, the addition of compound nucleating agents designed proved to has further effect in improving the crystallization rate, compares to pure PET, the crystallization rate has increased about 5 times, the onset temperature has increased about 50℃, it's crystallization behavior is similar to PBT.The nucleating mechanism was also discussed in the thesis, during the crystallization process, the low molecular nucleating agent plays a simply heterogeneous nucleation, while oganic acid salt and inomer can react with PET molecule chain in high temperature zone,and then then produce a new substance PET-Na with ionic ending group,the ion cluster is a really crystallization nucleus. When the organic acid and inomer are used thogethe, there exists cooperative function, the crystallization promting effect is better.On the basis of above study on nucleating agents, 30% glass fiber reinforcedPET engineering plastics was prepared via twin-screw extruding equipment, the tensile strength is 151MPa, flexture strength and modulus is 225MPa and lOGPa respectively, impact strength has reached 9.5kg-cm/cm and the HDT has raised to 218℃, the typical properties are close to the same product in the world market. The mould temperature has slowed down to about 70 ℃, the cycle time shortened remarkably, the molding condition is similar to PBT.