Preparation and characterization of plasticized poly(lactic acid) with epoxidized palm oil

Conventional plastics such as polyethylene, polypropylene, and polyethylene terephthalate persist for many years after disposal. They are inappropriate for applications intended for short time such as packaging, which increases the plastic waste disposal. The accumulation of plastic waste in landfills results in long-term environment, economic and waste management problems which need immediate resolution. Rising environmental concerns have directed research to the development of biodegradable polymer materials. Poly(lactic acid) (PLA) has a large potential as a biodegradable plastic. However, PLA has low toughness, low tensile elongation and high brittleness which limited its applications. In this research PLA was incorporated with three different samples of epoxidized palm oil (EPO). The plasticized PLA were prepared by melt blending technique using Brabender internal mixer. The effects of three different samples of EPO and their loadings on plasticized PLA were studied. Further, the optimum EPO loading with enhanced properties of PLA were determined. Results displayed the overall properties of PLA were improved with the addition of EPO. The optimum EPO loading with enhanced mechanical and thermal properties of PLA is 1 wt%. PLA/1 wt% EPO(3) showed excellent properties compared to PLA/1 wt% EPO(1), PLA/1 wt% EPO(2) and neat PLA. The tensile strength, flexural strength, impact strength and elongation at break were improved by 13%, 25%, 23% and 77%, respectively compared to neat PLA. This reveals good stress transfer of the material. Addition of 1 wt% EPO(3) also significantly decreased the storage modulus while increased the loss factor of DMA analysis. XRD analysis reveals an increase in the amorphous phase of the PLA/1 wt% EPO(3), whereas an increase in the crystalline phase of PLA/1 wt% EPO(1) and PLA/1 wt% EPO(2). Thermal properties of the plasticized PLA were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). From the results, there is significant improvement about 27% on the thermal stability of plasticized PLA with the addition of 1 wt% EPO. Further, the DSC results illustrate a decrease in the glass transition temperature due to plasticizing effect of EPO. The surface morphology of the PLA/1 wt% EPO(3) fracture surface obtained from tensile test shows a smooth surface without voids and aggregation, indicating good interaction between PLA and EPO(3). This is in agreement with the significant improvement of mechanical properties. The environmental degradation behaviors on the physical properties of plasticized PLA were studied with special reference to the influence of ageing conditions like water sorption and biodegradability. From water uptake analysis, it can be inferred that the 1 wt% plasticized PLA absorb lesser water than neat PLA. The soil burial test was carried out for 6 months, and the results indicate that EPO loading slightly promotes degradation of the plasticized PLA. Thus, PLA/1 wt% EPO(3) can be considered as an alternative to the conventional plastics used. Additionally, EPO can be seen as a potential useful plasticizer.

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