Synthesis And Application Of New PVC Thermal Stabilizers And Study On Their Mechanism

Polyvinyle chloride(PVC) is one of the five most popular plastics. Since it has poor thermal stabilization and will degrade at 160～200℃in its processing, thermal stabilizer is used. There are plumbum salts, organic stannum and Ca/Zn Composite Stabilizer in traditional thermal stabilizer. However, Plumbum salts thermal stabilizers pollute environment with toxicity, using organic stannum costs too much, and the phenomenon of "zinc burn" will easily occur during the process of using Ca/Zn Composite Stabilizer. As the demand for environmental protection is becoming stronger and stronger, it will be quite significant and promising to develop a new kind of thermal stabilizer with high efficiency and low toxicity.Rare earth thermal stabilizer, with no toxicity and long stabilization, has been developed as a new type of thermal stabilizer in the past few years, but it can not protect PVC from discoloring at an early stage. In my research I synthesize several rare earth salts by testing and choosing, only to find that Lanthanum stearate is the best one. The mechanism of stabilization of lanthanum stearate is studied by a series of experiments and tests, which can also be well explained by concerted elimination mechanism. I find that lanthanum stearate can not restrain the increase of conjugated double bond effectively; however, it can interact with chlorine in PVC, so that it makes C-Cl bond more stabilized and 1,3 rearrangement of chlorine more difficult. Consequently, it can restrain the formation of conjugated polyene(-CH=CH-)n (n>2). This theory can explain well the reason why rare earth salts can not protect PVC from discoloring at an early stage.In my research, cooperativity and cooperativity Mechanism of cylohexanediol diglycidyl ether and Ca/Zn Composite Stabilizer are studied.We find that cylohexanediol diglycidyl ether turns out to possess the feature of harmonious cooperativity with Ca/Zn composite stabilizer. It restrains the phenomenon of "zinc burn" effectively during the process of using Ca/Zn composite stabilizer, and it has an advantage over epoxidized soybean oil after being remixed with Ca/Zn composite stabilizer. There are two aspects for the cooperativity mechanism compounded by cylohexanediol diglycidyl ether and Ca/Zn composite stabilizer: One is to remove HCl during the degradation of PVC by the reactions that epoxidized groups and ether bonds react with HCl; The other is that the oxide atom in the epoxidized group can combine with zinc in the presence of ZnCl2, making ZnCl2...