Effect of organoclay loading on the crosslinking and degradation of irradiated ethylene(vinyl acetate) copolymer/natural rubber nanocomposites

The effects of organoclay loading and electron beam irradiation on the crosslinking and degradation of ethylene(vinyl acetate) copolymer (EVA)/natural rubber, grade Standard Malaysian Natural Rubber (SMR L) nanocomposites was studied. The nanocomposites were prepared through the melt blending technique with the ratio of EVA: SMR L fixed at 50:50 and organoclay loading varied from 0 to10 phr. The samples were irradiated using a 3.0 MeV EB machine with doses ranging from 50 to 200 kGy. At irradiation dose 50–150 kGy organoclay reduces the crosslinking yield significantly as evidenced from the gel fraction results and thus, storage modulus decreases and tan delta_max values increases for the nanocomposites compared to neat EVA/SMR L. However, at 200 kGy the crosslinking yield was not much affected by the organoclay and thus, the storage modulus increased and tan delta_max decreased. Scanning electron micrograph images show that different level of irradiation dose form different phase morphology on the nanocomposites. Analysis on Fourier transform infrared spectrums and carbonyl index values proved that the nanoscale dispersion and barrier effect of organoclay influence the crosslinking and degradation of the nanocomposites thus gives a significant effect on the dynamic mechanical properties.