Effect of Wood Content on The Thermal Behavior and on The Molecular Dynamics of Wood/Plastic Composites Gisele C. X. Valle, * 1 Maria I. B. Tavares, 1 Leandro Luetkmeyer, 1 Giovanni C. Stael 2 Summary: In the last decades, the growing environmental awareness has resulted in a renewed interest in the use of natural materials for different applications. In this context, the use of wood in plastic to obtain composites has grown significantly. In the present work, heartwood and sapwood from Angelim Pedra (Hymenolobiun petraeum) were used to prepare PVC/wood composites. To study the composites with different wood types and filler contents the molecular dynamic was investigated through low field NMR by poton spin- lattice relaxation time measurements (T 1 H) and the thermal behavior was characterized by means of differential scanning calorimetry (DSC) focusing the glass transition temperature and thermogravimetric analyses (TGA) observing the changes in the thermal stability. It was found that increasing addition of wood flour (sapwood and heartwood) caused a small but progressive improvement of the decomposition temperature of the composites, whereas the glass transition temperature remains practically unchanged. In the molecular dynamic behavior, a gradual decrease in T 1 H values was observed with increasing sapwood and heartwood content, indicating that the composites became less rigid. The distribution curves of the domains showed a better interaction and phase dispersion between the composite components with higher filler content. Keywords: composites; NMR; PVC; thermal properties Introduction Wood is a natural polymeric composite, made up mainly of cellulose, hemicellulose, lignin, and a small amount of extractives with approximately 45%, 22%, 25% and 8% of composition, respectively. [1–3] The use of wood as reinforcing filler in polymer composite has made significant gains in popularity due to their many advantages including economic, technical and ecological aspects. Their main benefits are: low cost, low density, high relative strength and stiffness, flexibility during pro- cessing with no mechanical harm to the equipment and because it is from natural renewable source, biodegradable and it provides a solution to environmental pollu- tion by finding new uses for waste wood. [4,5] To produce wood plastic composites (WPCs) both thermosets and thermoplas- tics polymers are attractive as matrix materials, however, thermoplastics offer advantages over thermosets: low processing cost, design flexibility and ease of molding complex parts are some examples. [4] The most commonly used thermoplastics are polyethylene (PE), polypropylene (PP) and poly(vinyl chloride) (PVC), representing 83%, 7% and 9% respectively of the whole markets in North America. [6,7] PVC is in particularly one of the most important commercial thermoplastic polymers and is Macromol. Symp. 2007, 258, 113–118 DOI: 10.1002/masy.200751213 113 1 Instituto de Macromole ´ culas Professora Eloisa Mano – Universidade Federal do Rio de Janeiro (IMA/ UFRJ). Centro de Tecnologia, Bloco J, Ilha do Fun- da ˜o. PO Box: 68525, CEP 21945-970, Rio de Janeiro, RJ- Brazil E-mail: gisele@ima.ufrj.br 2 Observato ´ rio Nacional – MCT, Rua Gal. Jose ´ Cris- tino, 77, CEP 20921-400, Sa ˜o Cristo ´ va ˜o, Rio de Janeiro, RJ- Brazil Copyright ß 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim