Properties of Kenaf Fiber/Polylactic Acid Biocomposites Plasticized with Polyethylene Glycol Razaina Mat Taib, 1 Suganti Ramarad, 1 Zainal Arifin Mohd Ishak, 1 Mitsugu Todo 2 1 School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, Nibong Tebal 14300, Penang, Malaysia 2 Research Institute for Applied Mechanics Kyushu University, Fukuoka 816-8580, Japan Biocomposites of kenaf fiber (KF) and polylactic acid (PLA) were prepared by an internal mixer and compres- sion molding. PLA was plasticized with polyethylene glycol (PEG) (10 wt%) and evaluated as the polymer matrix (p-PLA). Fiber loadings were varied between 0 and 40 wt%. The tensile, dynamic mechanical, and morphological properties and water absorption behav- ior of these composites were studied. Reinforcing effect of KF was observed when fiber loading exceeded 10 wt% despite of the inferior fiber-matrix adhesion observed via scanning electron microscopy (SEM). Un-plasticized PLA/KF composite exhibited higher tensile properties than its plasticized counter- part. Fiber breakage and heavily coated short pulled-out of fibers were observed from the SEM micrographs of the composite. The presence of PEG might have dis- turbed the fiber-matrix interaction between KF and PLA in the plasticized composites. Addition of PEG slightly improved the un-notched impact strength of the compo- sites. Dynamic mechanical analysis showed that the storage and loss moduli of p-PLA/KF composites increased with the increase in fiber loading due to increasing restrictions to mobility of the polymer mole- cules. The tan delta of the composites in contrast showed an opposite trend. p-PLA and p-PLA/KF compo- sites exhibited non-Fickian behavior of water absorp- tion. SEM examination revealed microcracks on p-PLA and p-PLA/KF surfaces. POLYM. COMPOS., 31:1213–1222, 2010. ª 2009 Society of Plastics Engineers INTRODUCTION Conventional and traditional fiber reinforced compo- sites are composed of carbon fibers or glass fibers in thermosets like unsaturated polyesters or epoxy [1] or other thermoplastic polymers like polypropylene (PP) and polyamide. These composites have been used for a variety of applications from structural to nonstructural such as those used in consumer products for casing, packaging, etc. Because composites are made using two dissimilar materials, they cannot be easily recycled or reused [2] resulting in disposal problems after their intended life. An option to overcome these problems is to develop compo- sites that are environmentally friendly, fully biodegradable and sustainable by combining natural fibers as reinforcing materials (or fillers) for biodegradable polymers to form biocomposites. Biocomposites may be used effectively in many applications such as mass-produced consumer products with short life cycles or products intended for one-time or short-term use before disposal [2]. At the end of their service life, biocomposite products can be com- pletely degraded in the environment or in waste infra- structures such as composting units without harming the environment [2–4], or can be alternatively incinerated for energy recovery [4]. Natural fibers such as flax, hemp, sisal, jute, and kenaf have long been realized as potential reinforcing materials or fillers in thermoplastics as well as thermosets. Natural fibers are of interest because of their advantages such as renewability, low density, nonabrasiveness during process- ing, high specific mechanical properties and more impor- tantly biodegradability. The main drawback of using natu- ral fibers is the lack of adhesion with the hydrophobic thermoplastic matrices which can be overcome with physical and chemical modification of either or both materials or by the use of compatibilizers [5]. It should be noted that the effectiveness of natural fibers to improve composite properties depends on various factors such as the fiber-matrix interfacial adhesion; type, aspect ratio, concentration, and orientation of the fibers, etc [6]. Now, the use of natural fibers has established in thermoplastic industry. Most of the present applications are in the trans- portation industry as more internal and only few external automotive components, building materials, and house- hold products. Correspondence to: Razaina Mat Taib; e-mail: razaina@eng.usm.my Contract grant sponsor: Universiti Sains Malaysia; contract grant num- ber: 304/227/PBAHAN/6035231. DOI 10.1002/pc.20908 Published online in Wiley InterScience (www.interscience.wiley.com). V V C 2009 Society of Plastics Engineers POLYMERCOMPOSITES—-2010