Improvement of the Processing of Polyurethane Reinforced by Glass and Cellulosic Fibres

摘要

Polyurethanes (PU) are well-known for their versatility in performance and processing which can be satisfied for various applications such as adhesive, coating, furniture, composite, etc. Depending on the type of monomers, formulation and processing used, PU products can be fabricated in different forms including panel, foam, fibre, and film, etc. In the composite market, PUs could take a more important place because several criteria have helped to increase its use relatively to other conventional thermosetting matrices such as unsaturated polyester or vinylester. Beside the great versatility of PU in term of processing the aspect of no volatile emission, such as styrene in polyester and vinylester resins, during processing and the ease of incorporation of renewable bio-based polyols in the PU resins are also the great advantages [1]. These research works on the processing of polyurethane composites have been conducted with two kinds of fibres. Glass fibres have been chosen because they are the most common used on the market and so are well documented. Cellulosic fibres, in this case flax fibres, are more and more considered for the reinforcement of polymers since they show many advantages in thermosetting composite including good mechanical properties, low density, biodegradability and a low energy consumption for composite fabrication. However, the structure of flax fibres is very complex. Each single flax fibre can be considered as a laminate composite reinforced by helical cellulosic fibres held in place by a matrix of non-cellulosic component (hemicelluloses, lignin, and pectin) [2]. Compared with glass fibres, which are continuous and isotropic, flax fibres are anisotropic and discontinuous (1 ≈ 30-40 mm)[3].