Study On Controllable Glycolysis And Polymerization Of Polycarbonate In Moderate Condition

Polycarbonate(PC) has excellent mechanical properties, ability to withstand high and low temperature, with good electrical performance, low water absorption, and good transparency. It is one of the thermoplastic plastics with excellent comprehensive performance. PC is widely used in the packaging, electrical appliances, automotive parts, and building materials. With the rapid increase in the production and consumption of PC, more and more waste PC is having been generated. Due to its non-biodegradability and the deficiencies of existing recycling methods, it is essential to find a way to cyclic utilize effectively. The effective recycling and cyclic utilization of PC wastes can reduce pollution for the environment, achieving the ultimate goal of sustainable development.The research content and the main results are as follows:(1) PC was depolymerizied using solution method with ethylene glycol(EG) as the glycolysis agent, zinc acetate as the catalyst, dioxane as the reaction medium. The main, two-factor interaction effects of reaction temperature, reaction time, amount of zinc acetate catalyst on the glycolysis of PC were discussed by 27 experiments. The sequence of effects on the glycolysis of PC in descending order was reaction temperature > reaction time > amount of zinc acetate catalyst, glycolysis temperature versus the glycolysis time > glycolysis temperature versus the amount of catalyst > glycolysis time versus the amount of catalyst, respectively. These effects were all have a significant impact on the glycolysis of PC. According to the 34 experimental design, the sequence of main factors was reaction temperature > reaction time > amount of EG> amount of zinc acetate catalyst. The controllable glysolysis of PC which got products with different molecular weight can be achieved under certain reaction conditions.(2) Controlled depolymerization of PC in EG was studied. The structure of glycolysis products had the same repeat unit with PC, and carried the OH end group. The effects of temperature, reaction time, amount of EG, amount and type of catalysts, the dosage and type of solvent on the depolymerization reaction were investigated. It was found that with the increase of temperature, the elongation of time or the increase of amount of EG, the viscosity number(VN) decreased gradually. The appropriate dosage of dioxane was 35 ml. The optimal content of zinc acetate was 1wt%. The results indicated that the depolymerization of PC in EG was a first-order kinetic reaction with the reaction activation energy of 35.7k J/mol.(3) The polymerization by glycolysis products of PC and adipoyl dichloride was studied by using solution polymerization. With the increase of the temperature, the difference value of VN(△VN) between glycolysis products under various temperature and copolymer gradually increased and a maximum was obtained when temperature was 80oC, and then decreased; the maximum difference value was 5.0ml/g. With the increasing of PC/EG mol ratio, the △VN between glycolysis products and polymerization gradually increased. When the PC/EG mol ratio was more than 2, the growth trend slowed down. The VN of copolymer gradually increase at first then decreased with prolonging the reaction time, and the optimum reaction time was 1.5h. The copolymer can be used as plasticizer, MFR of copolymer/PC blend is able to achieve 5 times of PC’s.