Influence of thermal oxidation on surface and thermo-mechanical properties of polyethylene

Blown low density polyethylene (LDPE) films added with oxo-biodegradable additive containing pro-oxidant were subjected to thermo-oxidation in an oven at 70 °C for varying time periods. The changes in mechanical and surface properties were studied using tensile strength, elongation at break, wettability, surface morphology using SEM, surface topology by AFM, functional groups by FTIR spectroscopy, absorbance spectra by UV-Vis spectroscopy. The thermally aged films with pro-oxidant additive added polyethylene (PE) exhibited a higher level of oxidation as revealed by increase in their carbonyl index than the pristine PE. In addition to it, the DSC melting behavior showed a slight increase in crystallinity (%C) and melting temperature (Tm) of the polymer containing oxo-biodegradable additive. The SEM micrograph reveals the increase in the size of cracks and grooves, according to the increase in the concentration of pro-oxidant additive. The surface roughness also supports the same through AFM image. The increase in the wettability and surface free energy of the thermally aged samples were attributed to the formation of hydrophilic groups on the polymer surface by thermo-oxidation. The pro-oxidant additive offers a new insight into the thermo-oxidation strategy for PE and can be widely used in packaging industry.