Received: 26 th Feb-2014 Revised: 26 th March-2014 Accepted: 29 th March-2014 Research article INVESTIGATION ON WATER ABSORPTION PROPERTY OF WOOD PLASTIC COMPOSITE Alireza Dorostkar 1 , Ali Rafighi 2 and Mehrab Madhoushi 3 1 Former M.Sc. Student, Dept. Of Wood Science and Technology, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran alirezadorostkar311@gmail.com 2 Assistant Professor. Dept. of Wood Science and Technology, Gorgan University of Agriculture Science and Natural Resources, Gorgan, Iran ali.rafighi@gmail.com 3 Associate Professor. Dept. of Wood Science and Technology, Gorgan University of Agriculture Science and Natural Resources, Gorgan, Iran mehrabmadhoushi@gmail.com Correspondence Address tel. +98 171 2245882 email: alirezadorostkar311@gmail.com ABSTRACT: In this research, the effect of wood species & particle size water absorption property of composite made of four species Fir, Beech, poplar and Alder sawdust and high density polyethylene were investigated. Wood plastic composite was made from dried Fir sawdust as filler at 70% ratio by weight and high density Polyethylene in batch process at 185 ˚C temperatures, at two particle sizes mesh 40 and mesh 80. MAPP was as coupling agent then were determined and compared their water absorption property according to ASTM D570 after 2 & 24 hour immersion at distilled water. Water absorption percent decreased in 3-12% range with increasing particle size. There were differences between different species water absorption property, but this difference did not significantly affect. Keywords: Wood-plastic Composite, water absorption, Particle size, Wood species, High density Polyethylene. INTRODUCTION There have been considerable increases in recent years on the production and application of wood–plastic composites (WPCs). Their properties and environmental advantages have made them a good choice for many applications [1, 2]. WPCs are made by combining wood and thermoplastic polymer, which results in a composite that combines the best properties of both components [3]. Wood often imparts strength and stiffness and is biodegradable, while the plastics afford ease of formation and moisture resistance [4, 5]. Effective use of wood- based particles and fibers as fillers or reinforcements in thermoplastic composites requires a fundamental understanding of the structural and chemical characteristics of wood [6]. The various wood species have different anatomies. These structural differences impact the use of these materials in WPC. For example, fiber dimensions, strength, variability and structure are important considerations [7]. Using diverse wood species and also sawdust from these species is regarded as a good opportunity to produce wood compounds with demanded properties and to supply compressed wood panels. It is essential to determine the properties of this new product. The moisture percent of this product influence in its other properties such as dimensional stability, mechanical properties, resistance to decay and etc. [8, 9]. The wood hydroxyl content affect on its water absorption. But in wood-plastic compound, physical and mechanical properties depend on the mutual effects between wood and thermoplastic material within the compound. Physical and mechanical properties of wood plastic composites (WPCs) generally depend on the properties of their components and the ratio of these components. One of the factors affecting properties of a wood component is wood particle size. The effect of this factor on WPC mechanical properties was mainly evaluated for typical WPCs containing small wood particles (wood flour) or short wood fibers [10]. Multi construct water resistance is improved by higher polymer rate [11]. Two distinctive parameters of wood are species and particle size. When fill is increased, water absorption elevates due to higher hydroxyl group [12]. They concluded that higher particle size leads to increasing of water absorption. International Journal of Plant, Animal and Environmental Sciences Page: 633 Available online at www.ijpaes.com