How surface treatment and/or reactive agents allow closed loop recycling of PLA/Flax and PLA/Bamboo reinforced composites to be performed ?
Résumé
Polylactic acid (PLA) composites with 10 wt% flax (FF) and bamboo (BF) fibers were prepared by melt mixing. Alkali pretreated fibers were treated by 3-aminopropyltriethoxysilane (APTES)[1-2]. A grafted copolymer with epoxy groups (Joncryl ADR 4468[3], acting as chain extender was used alone or in combination with the silane treatment.The influence of silane and/or Joncryl on the composite materials was investigated on the mechanical, thermal and thermomechanical properties of injection molding biocomposites. The adhesion of the fibres to the matrix was shown using SEM and FTIR. XPS indicated that chemical bonds were formed between silane and fibers. The combined used of Joncryl and silane in the corresponding composites (PLAJ-SFF and PLAJ-SBF), allowed a significant improvement of the thermal stability and interfacial adhesion to be achieved. With the silane-treated fibers, both tensile modulus and strength of the corresponding composites were improved. When adding Joncryl alone or in combination with silane, these mechanical properties improved further.Closed loop recycling was performed after hygrothermal ageing to simulate the lifetime of the composites and before grinding and reprocessing.All composites without modified fibres exhibited pull-out phenomena after recycling steps. The presence of Joncryl seemed efficient to maintain tensile strength, but mainly for PLA/Flax composites. Only the silane/Joncryl combination allowed the tensile strength to be conserved beyond 2 cycles of ageing and reprocessing.
