Oxidative Ageing and Structural Characterization of Naturally Weathered Low Density Polyethylene Films

Natural weathering was performed in a Saharan region to characterize its effect on low-density polyethylene (LDPE) films used for greenhouse coverings. The morphological changes, followed by differential scanning calorimetry (DSC), showed that the damages caused by the oxidation of tie molecules increased the lamellae thickness, its distribution and the crystallinity. Wide-angles X-ray diffraction (WAXD) was used to follow both the structural and morphological changes of the film. The WAXD crystallinity increase had the same trend as that determined by DSC. Field emission scanning electron microscopy (FESEM) of the films surfaces and cross-sections showed that the degradability increased with exposure time. Atomic force microscopy (AFM) analysis was used to evaluate changes in the surface morphology and roughness. Ageing caused a change of the surface topography of the LDPE films as observed by the increase of surface roughness which is indicated by the increase of the roughness parameters. Simultaneously the peaks-spacing (d) over bar decreased.