Hydrophilic flax fibers

Fibers are widely used in polymeric materials to improve mechanical properties. Vegetable fibers (e.g., cotton, flax, hemp, jute) can generally be classified as bast, leaf or seed-hair fibers. Cellulose is the major substance obtained from vegetable fibers, and applications for cellulose fiber-reinforced polymers have again come to the forefront with the focus on renewable raw materials [198 - 200]. Hydrophilic cellulose fibers are very compatible with most natural polymers. 

For instance, Soykeabkaew et al. (2004) prepared cellulose liber-reinforced starch-based composite foams (SCFs) by baking process. SCFs were prepared successfully by baking starch-based batters incorporating either jute or flax fibers inside a hot mold. Starch is an alternative material for making foams. Batters of starch and water can readily be baked in a closed, heated mold where the starch granules gelatinize and the evaporation of water causes the starch to foam out and take up the shape of the mold. Foams made from pure starch have major drawbacks on their brittleness and sensitivity to moisture and water. Since both the fibers and the starch matrix were naturally polar and hydrophilic, strong interaction between them was expected. 

Moisture relations in textile polymers are concerned mostly with the hydrophilic fibers, such as the cellulose groups of cotton, flax, hemp, jute, viscose, modal, and acetates. This is not to say however that the essentially hydrophobic fibers, which fall into the synthetic polymer group (see Fig. 1) have zero moisture imbibition or are totally unaffected by moisture, although this will be true for some of the fibers in this group. 

It is well understood that proper fiber-matrix bonding is crucial to the performance of flax composites (Mustata 1997). This drawback is due to the hydrophilic nature of flax, caused by the hydroxyl groups in the fiber s cellulose and lignin (Nevel and Zeronian 1987), and resultant poor interaction with polymers, which... 

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