18 TH INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS 1 General Introduction Wood Plastic composites(WPCs) market is going strongly around the world. It is commonly used as substitute or alternate for the natural wood which is wildly prohibited or legally controlled by many countries. Most applications of WPCs are as structural and decorative materials such as outdoor deck, floors, windows and doors. The main ingredients of WPC consist of thermoplastic polymer matrix and natural fiber reinforcement. The most common matrices are PVC, PP and PE. The wood flour obtained from timber milling is commonly used. The characteristic of the product varied depend largely on type of matrix and reinforcement. However, the commercially available wood composite has some incompetency such as low mechanical properties compare to those hardwoods. Therefore, the improvements of the long term properties have been explored by many researchers and engineers. The main techniques used for diversifying of WPCs include grafting, cross linking and blending of the matrix and reinforced with other high performance filler(s)[1, 5, 6]. Silane grafting and water crosslinking of polyolefin have received much attention in industrial applications and fundamental research, because of its provide the obvious advantages, such as easy to process, low capital investment, and favorable properties in the processed materials[4]. Silane group is grafted onto the polymer chain by, firstly, addition of peroxide to initiate free radicals that can induce the grafting of a silane group onto the polymer backbone. The resultant silane grafted polymer matrices is then hydrolyzed and condense to create –Si–O–Si– bonds between the chains. The bonds between wood and plastic have been suggested to comprise a mix of silane bridges and hydrogen bond[3]. This network results in the outstanding performance properties. In this studied, WPC based on crosslinked polypropylene and wood flour reinforcement was performed. As the crosslink structure of polymer chain enhances the properties of material such as higher in resistance to heat and outdoor degradation. Accordingly, it will give rise to superior in dimensional stability and durability. The statistical approach by mean of design of experimental(DOE) on the given constituent parameters that effect to the properties of WPC will be the prime interests. 2 Experimental 2.1 Materials Commercial grade isotactic polypropylene homopolymer(PP700J) for injection molding application(MFI = 12g/10min @230/2.16) supplied from SCG Chemical Co., Ltd. was used as the composite matrix. Vinyltrimethoxysilane(VTMS), Silquest A 171, as crosslinker or coupling agent was purchased from Optimal Tech Co., Ltd. General commercial grade Dicumyl peroxide(DCP) was employed as free radical initiator. Talc(JetFine 3CA) manufactured by Luzenac with the particle size of 1.1 µm was added as filler. Wood flour from timber mill was ground by hammer mill machine into fine powder with particle size, by mean of sieve size, less than 1 mm. Mixture of powders, Irganox 1076 and Irgafos 168, at weight ratio of 1:1 were used as thermal/processing stabilizer and available from Ciba specialty chemicals Co., Ltd. DESIGN OF EXPERIMENT: WOOD COMPOSITES BASED ON CROSSLINKED POLYPROPYLENE A. Khongrit 1,2 *, U. Meekum 1,2 1 School of Polymer Engineering, Suranaree University of Technology, Nakorn Ratchasima, Thailand 2 Centre of Excellence for Petroleum, Petrochemicals, and Advanced Materials, Chulalongkorn University, Bangkok, Thailand *holly2frozen@hotmail.com Keywords: Wood polypropylene composites, Crosslinked polypropylene, Design of experiment, sauna treatment