Study On The Quality And Processing Properties Of Bottle Grade Polyethylene Terephthal(Pet) Pellets

The bottle grade pellets of PET are formed through the solid state polymerization from the basic PET chips. In order to guarantee the transparency of the products such as bottles and embryos, some third monomer of Isophthalic acid is added to the reaction system to make co-monomer during the production of low IV polyester chips, which can depress the orderliness of the structure of molecules, increase the crystallized temperature, reduce the crystal rate and improve the chips'machining performance during the process of melt's injection and blown of bottles. In addition, some toner and thermal stability reagent is added to the system to meet the needs of color and ensure the reaction stability in high temperature and avoid the hot decompose. This paper introduced the production process and guide line of the bottle grade pellets of PET, analyzed and studied the factors which may affect the products'quality and machining performance and application, put forward the projects of how to improve the PET'quality, discussed some factors which can influence the melt's rheology performance of bottle grade chips of PET, then discussed the machining process of PET. Through the study of this paper, it was pointed out that the quality of the bottle grade pellets of PET is mainly depended on the prescription and quality character of basic PET chips and the production process of SSP. The thermal stability reagent and toner and catalyst added to the reaction system during the process will become the nucleus of the crystal, which will quicken the crystal, influence the machining performance and products'transparency. During the process of SSP, the increased range of IV relates to the route of process and state time and reaction temperature of SSP. It will favor the increasing of the chips'IV and decreasing of the acetaldehyde in products to heighten the reaction temperature or postpone the reaction time or increase the catalyst content of the reaction system, but these methods may influence the chips'color and other quality performance. The melt of PET is belong to non-Newton type liquid, PET chips'quality performance such as IV, -COOH contend, IPA contend, DEG contend and the processing temperature of chips will influence the melt's rheology and processing performance. During the production of bottles, the drying process of chips and the injection and molding process and the blown process of the bottles will influence the bottle's intension, transparency and other mechanical performances .