Factors that Affect Decay of Wood-Plastic Composites

7 FACTORS THAT AFFECT DECAY OF WOOD-PLASTIC COMPOSITES 

2 Wood Particle Size and Wood/Plastic Ratios 

WPCs containing large particles tend to experience more severe decay at similar wood ratios ( 50% wood) [23]. Large wood particles create more pathways into the plastic matrix, exposing more surface area to water and fungal hyphae. Simonsen et al. [45] noted similar effects using polyethylene and polypropylene. While small particles are preferable for slow moisture uptake, they are more costly to produce and therefore increase the final cost of the product. 

Mankowski and Morrell [10] examined the influence of the wood/plastic ratio and wood particle size on the decay of commercial WPCs made with pine and HOPE. A 20% wood weight loss was observed in the WPCs made with 70% wood (small wood particles) after exposure to a brown-rot fungus. In contrast, little or no degradation was observed in two samples of WPCs made with 50% wood content, despite the use of larger wood particles. These results suggest that the amount rather than size of the wood particles may have a greater effect on WPC durability [13, 22], 

Differences between the hydrophilic wood and the hydrophobic thermoplastic during processing can limit bond development, resulting in poor adhesion between wood fibers and the plastic polymer. Without chemical or physical bonding, failures on the wood-polymer interface and interfacial voids can develop because of poor processing or as a result of external factors, such as moisture uptake or UV degradation. These failures in the wood-polymer interface 

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