Water Absorption by Composite Materials and Related Effects

WATER ABSORPTION BY COMPOSITE MATERIALS AND RELATED EFFECTS 

One of the most remarkable features of composite materials is a relatively low water absorption compared to that of wood. This is one of the few properties due to which composites are clearly better than wood lumber. And better here is directly related to dimensional stability and a better durability of the material, first of all its resistance to microbial degradation. 

When a piece of wood is immersed in water, after 24 h its weight increases by about 25%. In other words, wood absorbs about 25% of water by weight for the said time period. After a much longer exposure time, wood can double its weight (100% water absorption). In trees, moisture content can range from about 30% to more than 200% by weight [I]. For wood-plastic composite (WPC) materials, these figures typically are 0.7-2% after 24 h, 1-5% after a week, and up to 18-22% after several months. 

Wood-Plastic Composites, by Anatole A. Klyosov Copyright 2007 John Wiley Sons, Inc. 

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