Characterization of photo-oxidative degradation process of polyolefins containing oxo-biodegradable additives

The effects of oxo-biodegradable additives on the photo-oxidation of four types of polyolefin polymers, namely high-density polyethylene (HDPE), low-density PE (LDPE), linear low-density PE (LLDPE), and isotactic poly-propylene (itPP) were investigated. Scanning electron microscopy, infrared spectroscopy, differential scanning calorimetry, and wide-and small-angle X-ray scattering were employed to gain insights into the chemical and structural modifications induced by the degradation process. The photo-oxidation preferentially occurred at the sample surface and was favored in the amorphous region of the polymers. The carbonyl index calculated for the neat and additive-containing samples suggested that the additives promoted the photo-oxidative degradation, particularly of the PE polymers, which are intrinsically resistant to oxidation, without altering their degradation pathways. The overall degradation rate of the additive-containing polymers was in the order of itPP > LDPE > LLDPE > HDPE.