COMPARATIVE STUDY ON DEGRADATION OF POLYLACTIC ACID/ SYZYGIUM AROMATICUM COMPOSITES AGEING IN OUTDOOR ENVIRONMENT AND SOIL BURIAL

Abstract

Major environmental problems resulting from non-degradable components of plastic wastes have awakened great attention to bioplastic as an alternative material. Among various bioplastic materials, polylactic acid (PLA) is recognised as a promising material especially as a food packaging material. The development of PLA composites using various fillers has extensively been in focus in order to preserve the high quality, safety, and extended shelf-life of packed food. Among the interesting fillers is Syzygium aromaticum (SA). SA, also known as clove, has biological activities such as antibacterial, antifungal, insecticidal, and antioxidant properties. This work investigated the effects of SA filler on the degradations of virgin PLA (VPLA) and recycled PLA (RPLA). The VPLA/SA composites and RPLA/SA composites were prepared using the solvent casting method. The content of SA filler varied in the range of 0 to 20 wt%. The composites were aged in outdoor environment and soil burial. The results revealed that the degradation rate was increased with the increase of SA filler in both ageing environments. After 10 weeks of ageing in the outdoor environment, the weight loss of VPLA/SA composites and RPLA/SA composites containing 20 wt% of SA were 7.7% and 12.8% respectively. Whereas in soil burial, the weight loss of VPLA/SA composites and RPLA/SA composites with similar SA content were 25.6% and 38.3% respectively. The degradation rate was observed to be more rapid in the soil burial as compared to the outdoor environment. Comparably, RPLA and RPLA/SA composites experienced higher degradation rates than VPLA and VPLA/SA composites. The degradation rate was consistent with scanning electron microscope (SEM) images which observed the formation of holes, cavities, cleavages, and grooves on the surfaces of the samples. Thermogravimetric analysis (TGA) results on aged samples showed that VPLA/SA composites and RPLA/SA composites that had aged in soil burial decomposed at lower temperatures. The shortening of degradation time of the VPLA/SA composites and RPLA/SA composites could increase their potential to be used as food packaging materials