Improved properties of thermoplastic wood flour composites

Sammanfattning: In this study the properties of composites made of wood flour and thermoplastics have been investigated. In order to improve the interfacial adhesion between hydrophobic and nonpolar thermoplastics and hydrophilic and polar wood flour different additives have been used as compatibilizers in composites systems. The interaction between a wood filler and thermoplastic matrix, with and without compatibilizers, has been studied using conventional mechanical testing, impact testing, dynamic mechanical thermal analysis (DMTA), electron microscopes and infrared spectroscopy. Tests of mechanical properties, such as maximum tensile strength, tensile modulus and impact strength have shown that maleic anhydride grafted styrene-ethylene/butylene-styrene triblock copolymer (SEBS-MA) acts as a compatibilizer in the composite system. The SEBS-MA improves the stress transfer from the matrix to the wood particles and forming an flexible interphase around the wood particle and therefore improves the impact properties. The DMTA measurements indicated that there is an interaction between the wood surfaces and the maleic anhydride part of the SEBS-MA copolymer, and also between PS and wood. Morphological studies with SEM and TEM showed that the addition of SEBS-MA improved the adhesion between the wood particles and polymer matrix and that the compatibilizer is located at the interphase region between them. An infrared spectroscopy study indicated that the MA in the SEBS may react with the wood by forming hydrogen- and esterbonds and also possibly interaction between PS and wood.