Effect on Moisture Content and Water Absorption

Obviously, the higher the density, the lower the moisture content in WPC boards, the lower water absorption by the boards, and the less swell and buckling, the less are the microbial contamination and microbial degradation. 

For the most dense GeoDeck deck boards (specific gravity 1.24-1.25 g/cm ), moisture content is aronnd 0.4-0.5% (brushed boards). For GeoDeck boards with much lower density (specific gravity 1.10 g/cm ) moisture content is around 1.7%. 

Generally, water absorption by composite materials depends on their porosity, amount of cellulose fiber, and their availability for incoming water. Because wood fiber in WPC is exposed into pores, it also increases water absorption by WPC. 

One can see that swelling is more pronounced with lower density boards than with high density boards, and the difference is even higher at a short-term water absorption. 

TABLE 6.9 Water absorption by GeoDeck tongue-and-groove boards having different density (specific gravity) and being submerged for a total of 28 days 

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