亚临界流体与高剪切应力对EPDM废胶粉脱硫反应的影响

Effects of High Shear Stress and Subcritical Fluids on the Devulcanization Reaction of Waste EPDM Rubber

在废旧三元乙丙橡胶粉(WEPDM)与未硫化三元乙丙橡胶(EPDM)混合物的熔融挤出过程中,采用改变亚临界流体品种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与高剪切应力对脱硫共混物DEPDM/EPDM的凝胶含量、门尼黏度、溶胶红外光谱及脱硫共混物共混三元乙丙橡胶与原EPDM共混再硫化材料EPDM/(DEPDM/EPDM)力学性能的影响,对再硫化材料的试样断面形貌也进行了扫描电镜观察。结果表明,亚临界流体水或醇的存在均能促进脱硫、解交联反应的进行,特别是在以亚临界乙醇水(7∶3)混合物作为反应介质的条件下,脱硫反应中交联S-S键断裂选择性明显增大,所得产物凝胶含量降低,门尼黏度增大,其再硫化材料力学性能也明显增加。挤出机的螺杆转速和脱硫反应温度均存在最佳值(220℃,600~800 r/min)。在以醇水混合物为反应介质的最佳条件下(220℃,600~800 r/min),其脱硫共混物共混EPDM再硫化材料EPDM/(DEPDM/EPDM)的拉伸强度和断裂生长率分别达到26.7 MPa和606.3%。

The devulcanization reaction of waste ethylene-propylene-diene monomer rubber(EPDM) during melt extruding process of the mixture with unvulcanized EPDM was investigated through compound-induced reaction in a twin screw extruder by increasing the screw rotation speed and in the presence of different subcritical fluids. The effects of subcritical fluids and high shear stress on the gel content,Mooney viscosity and FT-IR spectra of the devulcanized ethylene-propylene-diene monomer rubber blends(DEPDM/EPDM) sol were measured,and the mechanical prosperities and microstructure of the revulcanized devulcanized ethylene-propylene-diene monomer with EPDM blends(EPDM /(DEPDM/EPDM)) were characterized. The results show that subcritical water or subcritical alcohol can promote devulcanization reaction and increase selectivity of the crosslink breakage,particularly,when the subcritical mixture of ethanol and water(7∶ 3) acts as reaction medium,which decrease the gel content and increase the Mooney viscosity of the devulcanized blend and further increase the mechanical properties of the revulcanized blend EPDM /(DEPDM/EPDM). The screw rotation speed and devulcanization reaction temperatures exist the optimum value(220 ℃,600 r/min to 800 r /min). Using the subcritical mixture of ethanol and water as reaction medium(220 ℃,600 r/min to 800 r/min),the tensile strength and elongation at break of revulcanized blend EPDM /(DEPDM/EPDM) reach 26. 7 MPa and 606. 3%respectively.