42 通过高温聚合超支化生产聚苯乙烯 An experimental investigation of the free-radical high-temperature (>300 °C) polymerization of styrene/divinyl benzene in a steady-state continuous-stirred tank reactor is reported. Under these conditions, backbiting followed by β-scission, which is the dominant chain degradation mechanism, is very aggressive. This allows for utilization of large amounts of cross-linker, thus producing hyperbranched polymers with high cross-link density, without the formation of gel. We have also shown experimentally that the propensity of the system to gel depends on the ratio between the rate of propagation and the rate of backbiting/β-scission, which can be controlled by the operating conditions, such as reaction temperature, average reactor residence time, and solvent level. Thus, through these parameters, it is possible to control the polymer molecular weight and cross-link density, as well as the occurrence of gelation.Therefore, high-temperature polymerization in a continuous-stirred tank reactor provides an economic and reliable technique for producing polymers of hyperbranched nature that can find various unique applications in polymer technology.
49 Expanded poiystyrene（EPS）is an excellent iight filied material Expanded poiystyrene（EPS）is an excellent iight filied material. EPS has a lot of good properties，such as light mass，high strength，good chemical stability，nice watery stability，wonderful mechanical properties and convenience in construction，which is widely used in road engineering in foreign countries. Utilizing EPS can decrease excessive subsidence and discrepant subsidence of soft subgrade，reduce lateral pressure and dispiacement of bridge pier，and so on. Less researches and appiications of EPS have been carried out in China.
50 EPS应用于道路建设的特性分析1.密度小EPS 的密度由成型阶段聚苯乙烯颗粒的膨胀倍数决定，介于 kg / m3 之间，工程中常用密度为15和30 kg / m3 之间的EPS。2.耐久性EPS 在水中和土壤中化学性质稳定，不能被微生物分解，也不会释放出对微生物有利的营养物质。但在特定条件下白蚁可对EPS 造成破坏。EPS 在紫外线（UV）照射下一段时间后表面由白色变为黄色，材料在某种程度上呈现脆性。