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

Abstract

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.

Improving the properties of reclaimed waste tire rubber by blending with poly(ethylene‐co‐vinyl acetate) and electron beam irradiation

“…Upon 200 kGy irradiation, no changes were observed in the position and height of tan delta peak; however, broadening of the tan delta curve was obvious. This might be due to increased free side chains as a result of chain scission or oxidation of EVA (Giri et al, 2012, Munusamy et al, 2012 which introduces micro heterogeneity.…”

“…These nano sized fillers or substances could increase the stiffness of EVA matrix resulting in decreased ductility of the blends (Tadiello et al, 2015). Furthermore, nano fillers such as nanoclay (Munusamy et al, 2012, Munusamy et al, 2009) and carbon nanotubes , Jung et al, 2013 The following degradation process observed is associated with the intensive thermal depolymerization of the rubber backbone . The first degradation peak (Tmax1) was observed at 390 °C whereas the second degradation peak (Tmax2) was observed at 444 °C in derivative TGA curve which corresponds to two types of rubber in the RTR.…”

Thermochemical compatibilization of reclaimed tire rubber/ poly(ethylene-co-vinyl acetate) blend using electron beam irradiation and amine-based chemical

“…Migration of nano sized fillers or substances (indicated by arrows) from RTR into EVA phase was also noted both before and after irradiation. Some studies proved that nano filler such as nanoclay [36] and carbon nanotubes [37,38] can lower crosslink network density in samples at lower irradiation doses. Figure 15b, d show EVA phase entrapped within the RTR phase as indicated by the arrows.…”