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.