Effect of Silica Nanopowder on the Properties of Wood Flour/Polymer Composite Biplab K. Deka, Tarun K. Maji Department of Chemical Sciences, Tezpur University, Assam-784028, India Low-density polyethylene (LDPE), high-density polyeth- ylene (HDPE), polypropylene (PP), and polyvinyl chlo- ride (PVC) (1:1:1:0.5) were solution blended by using a mixture of solvents consisting of xylene and tetrahy- drofuran (THF) (70:30). SiO 2 nanoparticles were modi- fied by cetyl trimethyl ammonium bromide (CTAB). Wood polymer composites (WPC) were prepared by using polymer mixture, polyethylene-co-glycidyl meth- acrylate (PE-co-GMA), wood flour, and modified SiO 2 . X-ray diffraction (XRD) studies showed that the inten- sity of the peaks of polymer mixture decreased due to incorporation of SiO 2 . The dispersion of SiO 2 nanopar- ticles and morphological characteristics were exam- ined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The interaction between SiO 2 nanoparticles, PE-co-GMA, polymer mix- ture, and wood was studied by Fourier transform infra- red spectroscopy (FTIR). Tensile and flexural properties of the composites improved significantly due to the incorporation of SiO 2 nanoparticles. Thermal stability, hardness, flame retardancy, and water resistance capacity were also found to enhance. Maximum improvement in properties was observed by the inclu- sion of 3 phr modified SiO 2 in WPC. POLYM. ENG. SCI., 52:1516–1523, 2012. ª 2012 Society of Plastics Engineers INTRODUCTION Wood polymer composite (WPC) covers a wide range of area in composite field [1]. These are eco friendly, low cost consuming, biodegradable, and renewable [2]. The consumption of plastic materials has increased enor- mously due to their various advantages. The disposal of post-consumer plastic materials in the form of carry bags, packaging films, boxes, etc. causes environmental pollu- tion. The majority of the waste plastic materials consist of a substantial amount of polyethylene, polypropylene and less amount of poly(vinyl chloride), polystyrene, poly(eth- ylene terephthalate), etc. Recycling and reusing is one of the processes to reduce the environmental pollution caused by post-consumer plastic materials. The use of recycled plastic materials is restricted due to their poor mechanical properties. The properties can be improved if the waste plastics are combined with cellulosic materials. The nonconventional plant materials can be transformed into value added products by treating with waste plastics. In solution blending, the knowledge regarding the propor- tion of different polymers in the waste plastic is essential to optimize the solvent ratio. The situation becomes fur- ther critical due to the problems like separation and segre- gation of different kind of plastics, labels of the container, adhesives in the packaging film, etc. To overcome all these problems, it has been decided to use virgin poly- mers such as high-density polyethylene, polypropylene, poly(vinyl chloride) of different ratio instead of waste plastics for making composites. Ordinary polymer compo- sites are lacking in dimensional stability, thermal stability, mechanical properties, etc. Incorporation of wood flour to the polymer matrix enhances all these properties [3]. The wood flour acts as reinforcing agent to the polymer and hence improves various properties. One of the major dis- advantages of WPC is the poor interfacial adhesion between inorganic wood flour and organic polymer. This results in poor compatibility among the constituents and hence decreases the properties of the composites. To improve the miscibility between organic and inorganic phase, certain compatibilizers are used. The compatibil- izer enhances interaction between hydrophilic wood fibers and hydrophobic polymers and at the same time improves the interfacial adhesion among different thermoplastic materials. The addition of a small amount of maleated polypropylene to PP/cellulose composite has improved the mechanical properties of the composites [4]. The uses of glycidyl methacrylate [5] and polyethylene-co-glycidyl methacrylate [6] as compatibilizer for making wood poly- mer composite have been reported. In the polymer composites, different types of fillers are used for improving the thermal, mechanical as well as other properties. Among them, nanopowder is widely used as filler. The surface characteristics of nanopowders play a key role in their fundamental properties from phase transformation to reactivity. Due to a large fraction of surface atoms and a higher surface area, a nanopowder would be expected to be more active. A dramatic increase Correspondence to: T.K. Maji; e-mail: tkm@tezu.ernet.in Contract grant sponsor: Council of Scientific and Industrial Research (CSIR)-New Delhi; contract grant number: 01(2287)/08/EMR-II. DOI 10.1002/pen.23097 Published online in Wiley Online Library (wileyonlinelibrary.com). V V C 2012 Society of Plastics Engineers POLYMER ENGINEERING AND SCIENCE—-2012