Oak particles size effects on viscous-elastic properties of wood polyester resin composite submitted to ultraviolet radiation

The aim of this paper is to use dynamic mechanical analysis to examine the modifications of the elasto-dynamical properties of a composite made of small waste oak particles of various sizes (0.04 and 1 mm) and a polyester resin (440-M888 POLYLITE), subjected to photo-degradation by UV radiation and thermal degradations induced by temperature variations between 30 and 120 A degrees C. Oak (Quercus robur) waste particles used in this study were the unmerchantable by-product left after converting logs into lumber. The size of the waste oak particles significantly modifies the morphological and mechanical properties of lignocellulosic composites. On the other hand, UV radiation and thermal degradation are recognized as factors causing structural modification observed at the interface between the particles and the matrix. The rheological parameters (storage modulus E', loss modulus EaEuro(3) and damping tan delta) and the glass transition temperature were determined both before and after UV treatment with the DMA242 C Netzsch instrument. Structural morphological modifications related to the impact of photo-degradation on fibres and the matrix were observed with an atomic force microscope. A strong nonlinear effect of particle size on the mechanical and rheological properties of the composites was observed.