Electron Beam Irradiation: A Method for Degradation of Composites Based on Natural Rubber and Plasticized Starch.

Polymeric composites based on natural rubber (NR) and plasticized starch (PS) obtained by peroxide cross-linking have been subjected to electron beam irradiation in order to investigate their degradation. The amount of PS ranged from 10 to 50 phr and the irradiation dose from 150 to 450 kGy. Irradiation was performed in atmospheric conditions using a linear electron accelerator of 5.5 MeV. Changes in chemical, physical, structural, and morphological properties of composites were correlated with variables, such as PS loading and irradiation dose. Thus, mechanical properties, gel fraction, cross-linking degree, water uptake, weight loss in toluene/water were compared with those obtained before irradiation. The changes in structure and morphology were studied by Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy. Both PS loading and irradiation dose were found to be responsible for the degradation installing. Moreover, it has been shown that at the dose of 450 kGy, chain scission is dominant over cross-linking.