Effect of Organoclay on Photo-oxidation of Mulching Films Based on Low Density Polyethylene (LDPE)/ Ethylene-Vinyl Acetate (EVA) Containing Ca- stearate as a Pro-oxidant

Polymer materials have been increasingly accumulated in the environment and led to an interest in solving waste disposal problems through replacement of inert and non-biodegradable materials by biodegradable alternatives. A very high demand on low density polyethylene (LDPE)/ethylene-vinyl acetate (EVA) copolymers as suitable film materials applicable in the agricultural industry, because of their flexibility and high quality features, has particularly increased concerns over the degradation of these films. The effect of organoclay Cloisite15A and calcium stearate on the photo-degradation behavior of lowdensity polyethylene (LDPE)/ethylenevinyl acetate (EVA) (70/30) films was investigated in this study. First the best feeding sequence was found by X-ray diffraction (XRD) for nanoclay dispersion, and the extruded cast films of LDPE/EVA (60-80 μm) containing 2% w/w calcium stearate and 2% w/w organoclay were prepared. Photocatalytic degradation of the LDPE/EVA composite films was carried out under ultraviolet (UV-A) light irradiation for 72 h. The progress of degradation was followed by monitoring the changes incurred in the samples using Fourier transform infrared spectroscopy (FTIR) and carbonyl index calculation, thermogravimetric analysis (TGA) and tensile properties (tensile strength and elongation-at- break). It was observed that the LDPE/EVA samples with no additives did not exhibit significant changes when subjected to photooxidation but calcium stearate showed a strong accelerating effect on the rate of photooxidation of films. The presence of organoclay, in enhancing the mechanical, thermal and barrier properties, did not influence the photooxidation mechanism significantly. In other word, the susceptibility of LDPE/EVA composite containing calcium stearate and organoclay to photooxidation was similar to that of LDPE containing Ca-stearate.