Photoinitiated crosslinking of EPDM/inorganic filler blends and characterization of related properties

Photoinitiated crosslinking of ethylene-propylene-diene terpolymer (EPDM) blends filled with calcium carbonate, talc and calcined kaolin (CK) in the presence of benzil dimethyl ketal as photoinitiator and trimethylolpropane triacrylate as crosslinker and their related properties have been studied by different analytical methods. The results from gel content and heat extension determination show that the efficiency of photocrosslinking of EPDM increases with increasing the content of diene and its molecular weight. The EPDM blends with 100 phr different inorganic fillers can be photocrosslinked to gel content of above 60% by 5 s UV-irradiation under optimum conditions. Under the same conditions of irradiation, the orders of photocrosslinking rate and final gel content are EPDM/CaCO3 > EPDM/talc > EPDM/CK. The data from thermogravimetric analysis, dynamic mechanical thermal analysis, electrical properties, mechanical tests and scanning electron microscopy show that UV irradiation crosslinking apparently enhances the thermal stability, mechanical properties and electrical properties of the photocrosslinked EPDM/inorganic filler samples. Although the attenuated total-reflection FTIR data show that inorganic fillers can promote the surface photo-oxidation of EPDM/inorganic filler samples with increasing the irradiation time, the above related properties of the photocrosslinked EPDM blends irradiated within 5 s are enough to satisfy many applications in the cable industry.