亚临界流体挤出法复合诱导EPDM废胶粉脱硫化及动态交联热塑性弹性体制备

Effects of Shear Stress and Subcritical Fluids on Devulcanization of Waste EPDM Rubber and Preparation of Dynamically Crosslinked Thermoplastic Elastomers

在三元乙丙废胶粉(W-EPDM)与未硫化的三元乙丙橡胶(EPDM)熔融挤出过程中,采用注入亚临界流体和提高双螺杆挤出机螺杆转速的方法,研究了亚临界流体品种(水,乙醇/水混合物,丙醇)、螺杆转速、脱硫促进剂品种(烷基酚多硫化物450、二烯丙基二硫醚)对脱硫共混物(DGTR/EPDM)凝胶含量、门尼粘度、溶胶红外吸收光谱及脱硫共混物共混PP动态交联热塑性弹性体((DEPDM/EPDM)/PP)力学性能的影响,对动态交联热塑性弹性体材料的试样断面形貌也进行了SEM观察。实验结果表明:亚临界乙醇/水混合物(7/3)或亚临界丙醇条件对脱硫反应中S—S键的断裂具有较好的选择性,可引起废胶粉交联网络中S—S交联键断裂反应增加,而主链断裂反应下降,所得脱硫产物制备的动态交联热塑性弹性体材料中未熔融的凝胶颗粒尺寸较小,材料的力学性能明显增大;脱硫促进剂烷基酚多硫化物450具明显的促进脱硫反应的作用。在亚临界正丙醇的最佳挤出反应条件下(220℃,600rpm,促进剂450),所得脱硫共混物(DEPDM/EPDM)制备的动态交联热塑性弹性体材料(DEPDM/EPDM)/PP的拉伸强度和断裂伸长率分别达到17.1MPa和443%,其力学性能和断面形貌结构明显优于以传统罐式脱硫法所得的相应材料。

The devulcanization reaction of waste ethylene-propylene-diene monomer rubber(W-EPDM)during melt extruding process mixed with unvulcanized EPDM was investigated through a compound-induced reaction by increasing the screw rotation speed and being in the presence of different subcritical fluids in a twin screw extruder.The effects of subcritical fluids(water,ethanol/water mixture and propanol),screw rotation speed and devulcanizaion accelerators(alkylphenol polysulfides 450 and DADS)on the gel content,mooney viscosity,FT-IR spectra of the sol of devulcanized blends(DEPDM/EPDM)and the mechanical properties of dynamically crosslinked thermoplastic elastomer((DEPDM/EPDM)/PP)prepared by devulcanization blends and PP were measured,and fracture surface morphology of dynamically crossinked thermoplastic elastomer(DEPDM/EPDM)/PP was also observed by SEM.The results show that subcritical ethanol/water mixture or propanol has a better selectivity on S—S bond cleavage,leading to increase of the cleavage reaction of crosslinked S—S bonds and decrease of cleavage reaction of the main bonds in crumb rubber crosslinked network.The size of unmelted particles in dynamically crosslinked thermoplastic elastomer becomes smaller.The mechanical properties of revulcanized material increased significantly. The devulcanization accelerator alkylphenol polysulfides 450 has significant role in promoting devulcanization.The tensile strength and elongation at break of dynamically crosslinked thermoplastic elastomer(DEPDM/EPDM)/PP reaches to 17.1MPa and 443% respectively when the screw rotation speed and devulcanization reaction temperatures exist optimum value(220℃,600rpm)in the presence of subcritical propanol.The mechanical properties and facture surface morphological structure of it was significantly better than those of the corresponding material obtained by conventional devulcaniztion tank.