Analysis of the role of the main constitutive polysaccharides in the flax fibre mechanical behaviour

摘要

The role of the main cell-wall polysaccharide-constituents of flax fibres on their mechanical behaviour has been investigated. One sample of scutched flax fibres underwent a successive sequence of extractions (boiling water, EDTA, HCl, NaOH), and tensile tests on elementary fibres were carried out after each step. Results indicated a role of the primary cell-wall in the tensile performance of the fibres. Indeed, an increase of the TIII mechanical behaviour proportion was observed after the boiling water extraction. Furthermore, after EDTA extraction, a significant decrease of the strength at the tangent modulus threshold (312-153 MPa) and a significant increase of the strain at rupture (2.3-2.9%), occurred. Additionally, it was highlighted that the strength at rupture and the Young's modulus of flax fibres decreased after each extraction. In the secondary cell-wall, it was deduced that the matrix polysaccharides were involved in the load transfer whereas structuring polysaccharides enhanced the cohesion between cellulose microfibrils. At the end of the extraction sequence, fibres still had mechanical performances close to those of regenerated cellulose ones and exhibited a typical non-linear mechanical behaviour. Thus, it was hypothesized that microfibril reorientation phenomena can still occur after a NaOH extraction when fibres are mostly composed of cellulose. (C) 2015 Elsevier B.V. All rights reserved.