LAUSR

Abstract Lignocellulosic fibres such as hemp fibres have emerged as an attractive alternative to nonrenewable fibers in the reinforcements in polymer composites. These fibres are subjected to pretreatment prior fibre extraction. In hemp industry, the retting is the first treatment applied to the plant after harvesting in order to separate the fibres from the central woody part of the stem. This treatment is needed to be more understood because of its importance for the development of high-performance hemp biocomposites. In this study, the influence of field retting treatment and lab-scale retting treatment of hemp fibres harvested at the end of flowering (EF) and at the seed maturity (SM) respectively, on hemp fibres /polypropylene biocomposites was investigated. The results highlight that, regardless the harvest period (initial state of the fibres) and type of retting, the thermal stability of biocomposite increased gradually with retting duration due to the increase of thermal stability of the fibres. The decomposition temperature of the fibres harvested at EF and SM increased from 335 °C and 352 °C, respectively to 350 °C and 368 °C for fibres that retted during five weeks. Tensile strength and Young’s modulus of the biocomposites reinforced with fibres harvested at EF increase gradually until reaching a maximum (5 weeks) (46.0 ± 1.9 MPa and 4072 ± 196 MPa respectively), and then tends to decrease with a prolonged field retting (42.9 ± 1.6 MPa and 3627 ± 188 MPa respectively). In contrast, for biocomposites reinforced with fibres harvested at SM and retted in accelerated conditions, the tensile strength and Young’s modulus decreased rapidly from 44.9 ± 2.2 MPa and 3732 ± 291 MPa for unretted fibres to 39.9 ± 2.6 MPa and 3327 ± 183 MPa for five week retted fibres.