A STUDY OF POLY (LACTIC ACID) SELF-REINFORCED BIODEGRADABLE COMPOSITES

Recent concerns over the harmful effects on the ecology of long-lasting plastics have led to heightened interest in the commercial development of more environmentally sustainable materials. Attention has been paid to the biodegradable thermoplastic polymers, such as poly (lactic acid) (PLA). Furthermore, due to the difficulty in separating fibre and matrix of commercial composite for recycling after end-use, the concept of self-reinforced composite (SRC) has been developed in the last two decades. This study combines the biopolymer, PLA, with the concept of self-reinforced composite to design and manufacture biodegradable PLA self-reinforced composites. Differential scanning calorimeter is used to find a suitable processing temperature range of 140-160°C based on the melting behaviours of the PLA yarn and film. Since PLA is thermally unstable and lose molecular weight at high temperature, the weight loss of PLA fibre and film during the processing condition was examined by thermogravimetry. The results from thermogravimetry showed that there was no obvious weight loss found under processing temperature (140-160°C). Unidirectional PLA self-reinforced composites were produced under various processing conditions by means of fibre and film stacking method. Composites with sandwich and non-sandwich structures were tested by a desktop Instron tensile machine. The tensile properties of non-sandwich structure did not show significant change by increasing the processing temperature due to the high variation. However, the tensile strength and strain at yield of sandwich composites were decreased as the processing temperature increase; and the peak values of Young’s modulus and tensile stress at yield were reached at 147°C. Moreover, the intermediary film in the sandwich composite reduced the delamination and provided better matrix wetting, comparing to the non-sandwich one.