碱性白土PVC热稳定剂的表面改性及其表征

Surface modification and characterization of alkaline clay PVC heat stabilizers

以硬脂酸表面改性的碱性白土作为PVC热稳定剂,研究了在干法改性中改性剂硬脂酸用量、改性温度、改性时间对活化指数的影响。同时,利用XRD、FT-IR、DSC对其结构进行表征及分析。结果表明:活化指数提高,刚果红热稳定时间延长;最佳改性工艺条件为改性剂质量分数为2.5%,改性时间为2 h,改性温度为70℃,其活化指数达到了100%。硬脂酸对碱性白土的表面改性属于化学改性,生成了硬脂酸钙,蒙脱石层状结构未受影响,且能在高温下保持结构稳定。通过刚果红实验与铅盐、钙锌稳定剂进行对比,改性后碱性白土是高效的吸附型热稳定剂,安全无毒。

Alkaline clay is modified with stearic acid on the surface. It could be used as PVC heat stabilizer. The main factors affecting activation index have been studied in the dry modification. Meanwhile, the effect of modification is measured and characterized by XRD, FT-IR and DSC. The results indicate that when activation index is improved, thermal stability time is also extended. The optimum conditions are shown as follows：2. 5 wt. % of stearic acid,70℃ of reaction temperature and 2 hours of reaction time. Under the optimal condition, the activation index H can reach 100%. Surface modification of alkaline clays with stearic acid is a chemical reaction, which can produce calcium stearate. The layered structure of bentonite is not affected and the stable structure can be maintained at high temperatures. The alkaline clay is compared with lead salt and calcium zinc stabilizer by Congo red experiment. It indicates that the modified alkaline clay is an efficient heat stabilizer, safe and nontoxic.