交联聚乙烯回收料填充高密度聚乙烯的发泡特性

Foaming Characteristics of Recycled Crosslinked Polyethylene Filled High Density Polyethylene

采用机械粉碎法制备得到的交联聚乙烯回收料(RXLPE)填充高密度聚乙烯(HDPE)以提高其熔体强度,并用偶氮二甲酰胺(AC)作为发泡剂在烘箱实现了无压发泡。结果表明,RXLPE加入HDPE后界面相容,部分解交联RXLPE微团分散在HDPE中形成微观"网络"结构,减小了HDPE熔体流动性,但提高了熔体强度和拉伸黏度及"应变硬化"效应。加入发泡助剂氧化锌(ZnO)和硬脂酸锌(ZnSt2)时,AC分解温度从205℃降低到160℃左右,可在低温发泡形成更均匀、粒径更小的泡孔。低于30%含量,增大RXLPE用量可制备发泡率高和强度大的发泡品;RXLPE/HDPE为30∶70时,发泡倍率最高可达6倍多。RXLPE/HDPE同HDPE发泡体受压呈现典型的小变形线弹性、中变形塌陷和大变形密实化的三区行为;适量添加RXLPE和发泡助剂可改善后两区性能;过多RXLPE导致泡孔壁曲折而大变形时响应小。

High density polyethylene(HDPE)was filled with mechanical grinded cross-linked polyethylene recycled(RXLPE)to increase its melt strength.Such RXLPE/HDPE was foamed by agent azodicarbonamide(AC)to achieve free foaming in the oven.The results show that their interface is compatible when RXLPE is added to HDPE such that partially decrosslinked RXLPE microclusters are dispersed in HDPE forming micro-network structures,which reduces the melt fluidity of HDPE but improves the melt strength and extensile viscosity and the corresponding strain-hardening effect.When the foaming additives of zinc oxide(ZnO)and zinc stearate(ZnSt2)are added,the decomposition temperature of AC decreases from 205℃to 160℃,which renders the cells of foaming products more uniform and smaller.The foam products with higher foaming expansion ratios and higher compressive resistance can be prepared by increasing the content of RXLPE when being lower than 30%.The highest expansion ratio is more than 6 times for 30∶70 RXLPE/HDPE.RXLPE/HDPE foams behavior like HDPE’s showing typical three zones’behavior of linear elasticity at small strain,collapse plateau at middle strain and compaction at large strain.The performance of the latter two zones can be improved by adding appropriate amount of RXLPE and foaming additives.