Natural and controlled photo aging of LDPE: Changes in structural, molecular and surface characteristics

Environmental degradation of UV-stabilized low density polyethylene (LDPE) film was observed by mounting the film on model greenhouse and aluminum exposure racks. The performance characteristics of weathered film in terms of drop in percent elongation was observed by testing mechanical property. The variations at molecular chain level were recorded by the Gel Permeation Chromatography (GPC) and the surface and morphological changes were monitored by Scanning Electron Microscopy (SEM). The results clearly reveal that the polyethylene film mounted on the model greenhouse has presented higher rate of degradation as compared to the film mounted on racks. The controlled environment inside the greenhouse partially prevent the dissipation of thermal energy from the greenhouse plastic film during cool night hours and create a unique environment which influence higher thermal degradation in the mechanically strained plastic film from inside. The overall hostile parameters inside the greenhouse contributes as a dual degradation factor in the deterioration of polymeric film. The chain scission reaction was predominant during the degradation phenomenon in terms of drop in elongation and molecular weight. Surface characteristics also support higher degradation process in the film mounted on the greenhouse.