【作者】 王建；

【导师】 薛锋；

【作者基本信息】 华南理工大学 ， 材料学， 2016， 硕士

【摘要】 聚碳酸酯(PC)是性能优异的工程塑料,因其力学强度高、透光性和电绝缘性好而被广泛应用于建材、电子和汽车制造领域。PC是不可生物降解的塑料,随着环境问题的日益严峻,实现PC的回收和循环利用也更具有现实意义。本课题旨在研究实现PC降解的新途径,降低PC的回收难度,并扩展PC回收料的应用范围。论文的主要研究内容为:(1)采用乌氏粘度计测定PC原料的粘均分子量,测得PC的粘均分子量为29070,小于GPC测得的重均分子量47890,大于数均分子量20890。用裂解气相色谱质谱联用仪对PC的裂解产物进行了分析,结果表明,PC在高温氮气氛围下,主链中C-C键和C-O键断裂,最终产生以双酚A和各种酚为主的小分子。其中C-C键的断裂是产生脂肪烃基或苯基封端的主因,而C-O键断裂是产生羟基封端的主因。最终裂解产物主要为各种酚,其中双酚A的产率最高。研究PC在二氯甲烷中醇解反应,反应得到的最终产物为双酚A。对反应过程中产生的中间产物进行表征发现,PC在溶液中先降解为含甲基和羟基封端的低聚物,低聚物进一步与甲醇反应得到双酚A。这说明PC在溶液中先发生了链段的无规断裂,再进一步反应得到双酚A。裂解的方法需要高温条件,消耗的能量高,酚类产物丰富,需要较为复杂的分离手段,但各种酚的利用价值较高;醇解法需要使用有机溶剂,产物只有双酚A和碳酸二甲酯,利用价值低,但消耗能量低,回收方便。(2)为实现PC的可控降解,分别采用了化学法和挤出降解的方法。PC在二氯甲烷中与乙二醇反应,降解得到端羟基PC低聚物,数均分子量可达到2590。PC分别与双酚A或丙三醇挤出,得到端羟基低聚物。双酚A或丙三醇添加的量不同,对产物的玻璃化转变温度和结晶均有影响。化学法需要使用有机溶剂完全溶解PC,但反应温度低,副反应少;挤出降解法需要在挤出机中进行,反应温度高于250℃,容易发生副反应。但挤出降解法反应时间短,可连续实现PC的降解。(3)利用降解得到的端羟基PC低聚物与聚硅氧烷共聚,成功合成了PC-PDMS共聚物。与低聚物相比,共聚物的热稳定性好,通过改变反应条件可得到粘数不同的共聚物。共聚物与PC共混后,得到的材料加工流动性好,且缺口冲击强度得到提高。为提高材料的阻燃性,添加硼酸锌作为协同阻燃剂。加入硼酸锌后,当PC、共聚物和硼酸锌的比例为100:3:4时,材料的阻燃性能可以达到V0级,但缺口冲击强度和拉伸强度下降明显。更多还原

【Abstract】 Polycarbonate(PC) is one of the excellent engineering plastics with excellent properties. It is widely used in building materials, electronics and automobile manufacturing for its high mechanical strength, good transparency and excellent electrical insulating properties. PC is non-biodegradable plastic, and implementation of the recovery and recycling of PC has more practical significance as environmental problems is more and more challenging. The research is to find new ways to realize degradation of PC in order to reducing the difficulty of reusing PC and expanding the application scope of PC recycled materials. Main contents of the research are as follows:(1)Viscosity average molecular weight is measured by ubbelohde viscometer, which is higher than number average molecular weight and lower than weight average molecular weight. The pyrolysis behavior of PC at high temperature and nitrogen atmosphere is studied by pyrolysis-gas chromatography-mass spectrometry. Results show that there are small molecules in the pyrolytic products because of the homolytic cleavage of C-C and C-O. Aliphatic terminated products and phenyl terminated products originate from homolytic cleavage of C-C and hydroxy terminated products from homolytic cleavage of C-O. Final pyrolysis products are mainly all kinds of phenol, including bisphenol A having the highest yield. The final product is bisphenol A and dimethyl carbonate when PC react with methanol in methylene chloride. Firs, PC degraded into oligomers with Methyl and hydroxyl end capping. Than oligomers react with methanol to generate bisphenol A. Pyrolysis method requires high temperature conditions, high energy consumption and complex means of separation but the products have high value. Methanolysis method need low energy consumption and the products are easy to recycled.(2)Methods of chemistry and extrusion are used to realize controllable degradation of PC. Hydroxyl-terminated PC oligomer was prepared by reaction of PC and ethylene glycol or by extrusion of PC and bisphenol A or glycerol. Degradation products would have different glass transition temperature and crystallization by different dosage of bisphenol A or glycerol. Chemical method needs to use organic solvent, but the reaction temperature is low. Extrusion method needs high temperature with side effects but little reaction time.(3)PC-PDMS copolymer was synthesize through hydroxyl terminated PC oligomer and Chlorine terminated polysiloxane. Copolymer has better thermal stability compared with oligomer. After blended with copolymer, PC has better processing property and improved notched impact strength. Zinc borate was added to the blends as synergistic flame retardant to improve flame retardant of the material. When the ratio of PC, PC-PDMS and zinc borate was 100:3:4, Vertical Burning Test of the material can reach V0 but the notched impact strength and tensile strength decreased obviously.更多还原