Abstract: When it is added in poly(vinyl chloride)(PVC),lignin has the potential to improve the thermal stability of PVC due to its sterically hindered phenol structure.However the thermal stability of PVC-lignin blends is practically worse than that of PVC due to the poor miscibility between lignin and PVC.A novel method was adopted to improve the miscibility between lignin particles and PVC matrix in PVC-lignin blends.A copolyacrylate,poly(ethyl acrylate-co-acrylic acid)was prepared.Lignin was treated with the copolyacrylate,and blended with PVC.The results showed that the thermal stability of PVC-lignin blends was well improved after lignin was treated with the copolyacrylate.The temperature of onset decomposition was about 13℃ higher than that of control PVC and the temperature of rapidest decomposition was about 27℃ higher than that of control PVC.Microscopic morphology analysis confirmed that the miscibility between lignin and PVC matrix was well improved.The combination between hydroxyl of lignin and carboxyl of EA-AA copolymer and the smaller lignin particles in the blend weakened the dehydration of lignin.Therefore,the acceleration of lignin's dehydration on autocatalytic dehydrochlorination of PVC was retarded and the inhibition of lignin's sterically hindered phenol structure on the autocatalytic dehydrochlorination of PVC was strengthened.

Key words: polyvinyl chloride, lignin, blend, thermal stability, copolyacrylate

摘要： 木质素分子中含有阻碍酚结构,可抑制基于自由基连锁机理的反应。而聚氯乙烯(PVC)的热降解属于自由基反应,因此用木质素与PVC共混,共混物的热稳定性应高于PVC,但PVC与木质素直接共混物的热稳定性一般都劣于PVC。制备了丙烯酸乙酯(EA)-丙烯酸(AA)共聚物乳液并用其对木质素粉末进行包覆处理。用处理后的木质素与PVC进行共混制备成PVC-木质素共混物。用热重分析法研究了共混物的热稳定性,并据扫描电子显微镜观测结果,结合木质素分子结构推测了共混物热稳定性的改善机理。结果表明,木质素用EA-AA共聚物处理后,共混物的热稳定性得到了明显改善,且优于PVC参照样(其初始分解温度和最大分解速率温度分别比PVC参照样高13℃和27℃左右)。扫描电子显微分析表明,木质素经丙烯酸酯共聚物处理后,与PVC的相容性改善显著,在PVC基体中分散良好。木质素羟基与EA-AA共聚物羧基的结合和分散颗粒的减小有效减弱了木质素的脱水作用,抑制了它对PVC的自催化脱氯化氢的促进作用,从而有效发挥了它的阻碍酚结构对PVC自催化脱氯化氢过程的抑制作用。

关键词: 聚氯乙烯, 木质素, 共混物, 热稳定性, 丙烯酸酯共聚物