In the last decade there has been a remarkable growth world-wide in the production of biomaterial-based composites. In this context, so-called wood plastic composites (WPCs) are today mainly used in outdoor applications, e.g. as replacement for traditional preservative treated wood. In outdoor conditions, moisture sorption combined with temperature induced movements of the polymer matrix may cause e.g. warping, cupping and bowing of the composite boards, as well as microscopic wood polymer interfacial cracks. The objective of this presentation is to highlight some recent research results about the micromorphological effects of moisture sorption and durability to attack by fungi of WPCs made from chemically modified wood. The modification methods used were acetylation and heat treatment. The technique used for studying the composite micromorphology was based on LV-SEM (low-vacuum scanning electron microscopy) combined with a specially design specimen preparation technique by UV-laser ablation. The results show that the UV laser technique is a very powerful technique for preparing surfaces of WPC for micromorphological studies without adding critical physical artefacts due to the preparation technique itself. Results also show that a water uptake and drying cycle in the WPC results in severe inner micro-cracks and wood-polymer interfacial debonding. These effects are, however, greatly reduced for WPCs made from the modified wood. Results also show that WPCs with modified wood are highly resistant to decay by fungi.
Keywords: Acetylation, heat treatment, thermoplastic composites, decay, moisture sorption, UV laser, micromorphology, soil tests
Authors
Segerholm B.K.
KTH, Royal Institute of Technology, Building Materials, Stockholm, Sweden
Rowell R.M.
USDA, Forest Service, Forest Products Laboratory, Madison, USA
Larsson-Brelid P.
SP Technical Research Institute of Sweden, Borås, Sweden
Wålinder M.E.P.
KTH, Royal Institute of Technology, Building Materials, Stockholm, Sweden
SP Technical Research Institute of Sweden, Borås, Sweden
Westin M.
SP Technical Research Institute of Sweden, Borås, Sweden
Söderström O.
KTH, Royal Institute of Technology, Building Materials, Stockholm, Sweden
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