Study of water behaviour of chemically treated flax fibres-based composites: A way to approach the hydric interface

Abstract

Please cite this article as: Alix, S., Lebrun, L., Morvan, C., Marais, S., Study of water behaviour of chemically treated flax fibres based composites: a way to approach the hydric interface, Composites Science and Technology (2011), doi: 10.1016/j.compscitech.2011 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractSilane (Si) and styrene (S) treatments were applied on flax fibres in order to improve their adhesion with a polyester resin and to increase their moisture resistance. The water sorption and permeation kinetics of the composites were correlated with the water sorption behaviour of untreated and treated fibres. An increase of the water barrier effect was observed in treated fibres-based composites in comparison with untreated ones. This was related to the shift-down of water solubility and to a decrease of the water diffusivity in treated fibre-based composites. In the case of (S) treatment, the presence of styrene increased the moisture resistance of the treated fibres and made compatible the fibres and the matrix. In the case of (Si) treatment, a good hydric fibre/matrix interface was obtained due to crosslinking reactions and hydrogen bonding between water molecules and free hydroxyl groups of (Si) treated fibres. In order to interpret water permeation behaviour of composite films, a simple illustrated model is suggested and represented by a schematic view.

Environmental resistance of flax/bio-based epoxy and flax/polyurethane composites manufactured by resin transfer moulding

“…When the composites are reinforced with flax unidirectional fibres (UD) or textiles, the fibre volume fraction usually drops to 30-35%. At maximum, the fibre volume fraction can reach 40% [11,12,14,17,58]. The challenge is to increase the fibre volume fraction and use tailored textiles to improve the mechanical properties of flax fibre composites and reduce the impact of fibre defects [50].…”

“…In fact, a hydrophobic matrix adheres poorly with hydrophilic natural fibres. To improve the strength at the interface, different chemical pre-treatments have been applied to natural fibres; however the results were mitigated [6,11,45,[51][52][53][54]. Mercerization, acrylation, acetylation and the grafting of coupling agent such as silane, maleic anhydride, peroxide or permanganate are the most studied pre-treatments.…”

“…Several studies have shown that the mechanical properties of natural fibres composites are strongly affected by moisture absorption [3,4,[11][12][13][14][15][16][17][18][19][20][21][22][23][24], but for now there is no clear understanding of the exact combination of water absorption mechanisms. Strong bonds between the fibres and the matrix will maximize the mechanical performance of the composite as well as preventing the infiltration of water at the interface [20,25].…”

“…Thereafter or maybe simultaneously, the fibres will diffuse/absorb water due to their hydrophilic nature (3). Fibres can also act as "water tank" by trapping water into micro-and macro-voids of the fibre bundle [11]. Because the core of the fibres is hollow, we can wonder if some of the absorbed water would be able to flow inside the fibres, which could act as channels for water (4).…”

Effect of jute fibre treatment on moisture regain and mechanical performance of composite materials

“…The surface of natural fibers is generally chemically modified to minimize the wetting of fibers in addition to improve the interface between the matrix and the reinforcement. Some chemical surface modification techniques include treatment with sodium chlorite [4], methaacrylate [5], isocyanate [6], silane treatment [7], mercerization, acetylation [7], etherification [9], enzymatic treatment [10], peroxide treatments, benzoylation [8], dicumyl peroxide treatment [6], plasma treatment [11], ozone treatments [12], and grafting. The oxidation of polyolefins [13], has also been described to improve the incompatibility between the surfaces of natural fiber and polymer matrix.…”