Consolidation of Naturally Occurring Polymers

The idea of self-reinforced fibre composites is not limited to the use of synthetic polymers as precursors. In the early 1990s, Wyler et al. reported the creation of a 

More recently, cellulose fibres have been investigated as potential precursors for self-reinforced polymer composites, as well summarised in a review by Eichhom et al. [191]. Numerous authors have reported the use of cellulose fibres from various sources, including wood pulp fibres [192, 193], filter and Kraft paper [194-197], microcrystalline cellulose fibres [198-202], sisal fibres [203, 204], ramie fibres [205], cotton fibres [206], regenerated cellulose (Lyocell) and cellulose fibres spun from an anisotropic phosphoric acid solution (Bocell) [207], and fibres from bacterial cellulose [208]. Two main technologies have been presented to produce these so-called self-reinforced cellulose or all-cellulose composites, and these are, first, the conventional impregnation of cellulose matrix into cellulose fibres and, second, a novel selective dissolution method in which the cellulose fibre surfaces are partially dissolved to form a matrix phase that bonds fibres together. 

Unlike the thermal processing methods for the consolidation of polymers such as PP, which may use selective fibre surface melting, selective dissolution of cellulose fibres partially dissolves the surface layer of cellulose fibres to form a matrix phase of the all-cellulose composites. Analogous to thermal processing methods described earlier, only the surface of the fibre is intended to be affected by the solvent processing and the core of the fibres maintain their structure in order to provide mechanical reinforcement for the final composite. If performed in a controlled manner, this selective surface dissolution concept can result in a continuous 

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