COMPATIBILISERS IN WOOD-POLYETHYLENE COMPOSITES AND THERE INFLUENCE ON THE MECHANICAL PROPERTIES AND WATER ABSORPTION
In this paper the improvement of the compatibilisation between wood particles and HDPE-matrix composites was investigated. A series of methods of compatibilisation and modification of the composite were performed and compared. The objective was to find the most suitable method for industrial up scaling, based on mechanical properties obtained. The tensile test of samples was performed, before and after water absorption investigation. Water absorption of composites was studied at two different temperatures: 25°C and 50°C. The water absorption kinetics was studied and it was found that water is absorbed in composites following the kinetics described by the Fick`s diffusion theory. After absorption, an important loss of properties was observed, due to the destruction of the wood structure due to the water absorbed.
Thermoplastics Reinforced with Wood Fillers: A Literature Review
Abstract Problems concerning the processing of thermoplastics reinforced with wood fillers are discussed. The high level of moisture absorption by the filler, its poor wettability, as well as the insufficient adhesion between untreated filler and the polymer matrix are reasons for the low tensile strength and high moisture sorption of composites. These shortcomings of composites can be prevented by the modification of the interface. The fiber-matrix compatibility and the composites properties can be improved by using some physical (e.g., steam explosion, corona, cold plasma) and chemical (cross-linking and acetylation of cellulose, grafting, use of coupling agents) methods. Modified wood-polymer interaction mechanisms are complex and specific for each definite system and processing conditions. Cellulose cross-linking and acetylation reduce hygroscopicity and swelling of wood and wood composites. Grafting of styrene to wood is effective for wood-polystyrene systems. The best coupling agent for wood-thermop...
Effects of material parameters on the diffusion and sorption properties of wood‐flour/polypropylene composites
Composites of wood in a thermoplastic matrix (wood–plastic composites) are considered a low maintenance solution to using wood in outdoor applications. Knowledge of moisture uptake and transport properties would be useful in estimating moisture-related effects such as fungal attack and loss of mechanical strength. Our objectives were to determine how material parameters and their interactions affect the moisture uptake and transport properties of injection-molded composites of wood-flour and polypropylene and to compare two different methods of measuring moisture uptake and transport. A two-level, full-factorial design was used to investigate the effects and interactions of wood-flour content, wood-flour particle size, coupling agent, and surface removal on moisture uptake and transport of the composites. Sorption and diffusion experiments were performed at 20°C and 65 or 85% relative humidity as well as in water, and diffusion coefficients were determined. The wood-flour content had the largest influence of all parameters on moisture uptake and transport properties. Many significant interactions between the variables were also found. The interaction between wood-flour content and surface treatment was often the largest. The diffusion coefficients derived from the diffusion experiments were different from those derived from the sorption experiments, suggesting that different mechanisms occur. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 752–763, 2007