Soil Burial, Hygrothermal and Morphology of Durian Skin Fiber Filled Polylactic Acid Biocomposites

INTRODUCTION Durian husk or skin is the waste product after the consumption of the durian fruit, which is known by local as the “King of fruits” [1]. The disposal of durian husk especially in landfill has caused various environmental issues such as soil contamination and disease spreading. The utilization of the natural fiber obtained from durian husk is seen as a potential solution to reduce the waste disposal and to diversify the usage of agricultural waste. The natural fiber is more eco-friendly and is seen as a suitable replacement for synthetic fiber. The natural fiber is lightweight, non-abrasive, renewability and biodegradability, which found applications in many fields ranging from a consumer product to the automotive industry. The examples of natural fibers are fruit fibers, wood, silk, ramie, jute, hemp, kenaf, sisal, coir, flax and bamboo [2]. The natural fiber obtained from agricultural waste such as durian skin fiber (DSF) is inexpensive and can be used as a reinforcement agent in a polymer matrix to form biocomposite. Biocomposite can be referred to a multi-phase material in which reinforcement fillers are added and integrated into a polymer matrix, resulting in synergistic properties that cannot be achieved from either component alone [3]. Polylactic acid (PLA) is one of the most common biopolymers which is derived from a renewable resource. PLA has attracted much attention due to its advantages such as high strength, high modulus, compostable and regarded as a safe material for food packaging application [4]. However, the disadvantages of the PLA are having low thermal stability and low elongation property. Previous works have been carried out to improve the performance of the PLA by adding reinforcement agent or filler to form biocomposites. Sun et al. [5] reported the good interfacial adhesion between the PLA and treated coir fiber was attributed to the pretreatment of fiber, which led to the improvement in tensile modulus and impact strength. According to Koay et al. [6], the addition of untreated DSF increased the tensile strength and modulus of the recycled polystyrene foam/DSF composites but decreased the elongation at break. The good interfacial adhesion between the natural fibers and the matrix is important for the superior properties, and this can be achieved via physical or chemical methods. Physical methods include plasma and heat treatment of natural fiber. Meanwhile, chemical methods include alkaline treatment, acetylation and the use of coupling agent [7]. In this study, DSF was obtained from durian husk and treated with an alkaline solution (sodium hydroxide) to remove lignin, hemicellulose, wax, and oil covering the external surface of the fiber cell wall [8]. The chemical composition of the DSF was Abstract