Investigation the photo-degradation of low-density polyethylene containing pro-oxidant and photo-catalyst

Research subject:

Low biodegradation rate of plastics, especially different grades of the polyethylene leads to many environmental problems. To reduce these effects, pro-oxidant added to the polyethylene to increase the photo-degradation and subsequently the bio-degradation rate of the polymer matrix. Besides the pro-oxidant, it seems that the photocatalysts can affect on the photo-degradation of the polyethylene and the subject of this study is to examine this idea.

Research approach: 

Photodegradable films of LDPE were prepared by melt blending of the polymer with cadmium selenide (CdSe) and trisilver phosphate (Ag3PO4) as photo-catalysts and manganese stearate as pro-oxidant. The samples were irradiated with visible and ultra-violet light. Scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC) and viscometry measurements were used to investigate the microstructure of the films.

FTIR spectra indicated to increment of the carbonyl index (CI) and vinyl index (VI) of the samples with photo-catalysts. In addition, SEM imaged confirmed higher and more homogeneous photo-degradation for these samples in comparison with other ones. Also, the dynamic-mechanical-thermal analysis showed that the polyethylene samples without the additives had higher modulus compared to other samples. However, the crystallinity of the samples with photo-catalysts increased due to nucleating agent effects of their particles. The viscosity of the samples containing the photo-catalysts and  pro-oxidants decreased significantly and the modeling results showed that this decrement  was due to the polymer chain degradation and reduction of their molecular weights. In general, the results showed that the combination of the photo-catalysts and the pro-oxidants had synergistic effect on the photo-degradation of the LDPE and accelerates its degradation process a lot more in comparison when only the pro-oxidant was used.