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以硫代乙酰胺、硝酸铋、硝酸镍、钼酸铵为主要原料,采用回流法合成了热敏催化剂MoS_2/Bi_2S_3/Ni_3S_4,将其与低密度聚乙烯(LDPE)熔融共混制得复合薄膜,并置于黑暗烘箱中热催化降解。通过SEM、EDS、AFM、TG、GPC、FTIR及力学性能测试,对热敏催化剂的结构和复合薄膜的热降解性能进行了考察。结果表明:纯聚乙烯薄膜在黑暗条件、55℃下热降解60 d后,热分解温度仅降低2.3℃,相对分子质量减小了17 451;而复合薄膜的降解效果明显优于纯聚乙烯薄膜,添加质量分数4%热敏催化剂的复合薄膜的热分解温度下降了20.5℃,相对分子质量减小了92 408,断裂伸长保留率低于5%,拉伸强度保留率低于20%,表面粗糙度明显增加且周围出现了不同程度的褶皱与鳞片状结构,甚至于剥落现象。此外,添加热敏催化剂的聚乙烯膜在降解过程中会出现大量的活性基团(·OH和HOO·等),可使聚乙烯发生链段降解,从而导致其分解温度降低。
The thermosensitive catalyst MoS_2 / Bi_2S_3 / Ni_3S_4 was synthesized by refluxing method with thioacetamide, bismuth nitrate, nickel nitrate and ammonium molybdate as the main raw materials, and then melt-blended with low density polyethylene (LDPE) , And placed in a dark oven thermo-catalytic degradation. The structure of the thermosensitive catalyst and the thermal degradation of the composite films were investigated by SEM, EDS, AFM, TG, GPC, FTIR and mechanical properties tests. The results showed that the thermal decomposition temperature of pure polyethylene film decreased only by 2.3 ℃ and the relative molecular weight decreased by 17 451 after being thermally decomposed at 55 ℃ for 60 d under dark conditions. The degradation of composite film was obviously better than that of pure polyethylene film , The thermal decomposition temperature of the composite film with 4% mass fraction of heat-sensitive catalyst decreased by 20.5 ℃, the relative molecular weight decreased by 92 408, the retention of elongation at break was less than 5%, the retention of tensile strength was less than 20% Surface roughness increased significantly and around the emergence of varying degrees of folds and scale-like structure, and even the phenomenon of spalling. In addition, a large amount of active groups (· OH and HOO · etc.) appear in the polyethylene film with thermal catalyst added during the degradation process, which can cause segment degradation of the polyethylene, resulting in a decrease of its decomposition temperature.