Study On New Process Of Synthesis And Modification For PET And Preparation Of Its Alloy Materials

Polyethylene terephthalate (PET) has been widely used in package, electronic, health and medical,construction, and automobile fields with its low cost and high performance.However, there still exist some shortcomings such as hard rigidity, poor toughness and low crystallization rate for PET. Modified PET through chemical route can endow new-type polyesters with excellent performances and expansive applications of polyester products with good prospects.In this thesis, PET modified with CHDM(1,4-cyclohexane dimethanol) co-polyester (PETG or PCTG) was first prepared by using terephthalic acid (PTA), ethylene glycol (EG) and 1,4-cyclohexane dimethanol (CHDM) as raw materials through melt polycondensation method. Then, PC/PETG, ABS/PETQ PET/PETG, PPS/PETG and other alloy materials were fabricated by melt blending process route.Besides, alumina sol (Al2O3) modified PET material was synthesized by using in-situ polymerization process.The morphology, structure, crystallization behavior, mechanical and thermal propertied of the above-mentioned material were studied. The thesis is divided into three parts:1.Synthesis and properties of co-polyester modified with CHDM.2.Preparation, structural and properties of PETG co-polyester.3.Synthesis and characterization of modified PET with alumina sol.The innovation results of above research are listed in the following:1.Novel catalytic system and synthesis route were created for the copolyester modified with CHDM. The new highly efficient catalytic system is suitable for the direct esterification process, making polyester chips with good color shade of b value, high intrinsic viscosity. The product quality can achieve the criterion of foreign advanced product. The PETG esterification technology triggered by using PET alcoholysis mother liquor at atmospheric pressure is suitable for industrial application. Based on the independent research and development of the PETG copolyester material, the systematic evaluation of PETG copolyester processing performance showed that PETG co-polyester products can replace the imported products in domestic.2.This design idea, which properties improvment of four kinds of alloys for PC/PETG, PET/PETQ ABS/PETG and PPS/PETG were proposed through blending on the basis of PETG,and the purpose was obtained by systematicly research. For the PC/PETG alloy, the use of PC and PETG has good compatibility to improve PC stress cracking and processing performance,and reduce the product cost through the partial replacement of PC.For the PET/PETG alloy, the toughness of PET is improved. For the ABS/PETG alloy, the partial replacement of PC/ABS material in the automotive and electrical industry can reduce the high-grade engineering plastics cost. For the PPS/PETG alloy, the influence of PETG on the crystallization behavior of PPS was studied.3.The project about improvement of PET thermal performance by PET modified with alumina sol was proposed. PET developed toward package material is rather limited, due to its thermal resistance. Currently in-situ polymerization technology refers to addition of SiO2 Nanocomposites and MMT. There is not reported that PET is modified with alumina sol according to the international literature.In this paper, in-situ polymerization technology of PET modified with alumina sol was adopted. The glass transition temperature of the modified PET increases from 72℃to 87℃and the crystallization rate significantly improved.