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