Effects of photo-oxidative degradation on low-density polyethylene (LDPE)

Exposure to solar rays can cause significant degradation in several substances. Photo-oxidative degradation due to the effect of UV radiation results in splitting of the polymeric chains, producing free radical and reducing the molecular weight of polymer, causing deterioration of its mechanical properties
and converting it into useless materials, after a certain period of time. The photo-oxidative nature of polyethylene has been investigated by FTIR, TGA, DSC, SEM, EDX, XRD and weight loss measurement. In the study performed an increase in carbonyl index, vinyl bond index, internal double bond index and percent crystallinity was observed after sunlight exposure. SEM micrographs revealed cracks and erosioned surface over the LDPE films after the treatment. Weight reduction and decreased carbon content was also observed in treated LDPE films. The results obtained clearly signify that LDPE undergoes a major degree of oxidation and an increase in crystalline fraction. If the LDPE is pretreated by an appropriate radiation they can become suitable for biodegradation without necessity of adding organic agents or photosensitizers. The photo-oxidative degradation of LDPE can be cost incentive and ecofriendly technique to deal with the plastic pollution in the future as the other methods available to deal with plastic waste such as incineration, ozonolysis and dumping of waste at landfill sites impose major threat to the environment.

Keywords – Carbonyl index, Vinyl bond index, Internal double bond index, Crystallinity, Enthalpy change.