Modifications de l’interface pour des composites recyclés fibres naturelles/PLA

National audienc

Modifications de l’interface pour des composites recyclés fibres naturelles/PLA

National audienc

How surface treatment and/or reactive agents allow closed loop recycling of PLA/Flax and PLA/Bamboo reinforced composites to be performed ?

International audiencePolylactic acid (PLA) composites with 10 wt% flax (FF) and bamboo (BF) fibers were prepared by meltmixing. Alkali pretreated fibers were treated by 3-aminopropyltriethoxysilane (APTES)[1-2]. A graftedcopolymer with epoxy groups (Joncryl ADR 4468[3], acting as chain extender was used alone or incombination with the silane treatment.The influence of silane and/or Joncryl on the compositematerials was investigated on the mechanical, thermal and thermomechanical properties of injectionmolding biocomposites. The adhesion of the fibres to the matrix was shown using SEM and FTIR. XPSindicated that chemical bonds were formed between silane and fibers. The combined used of Joncryland silane in the corresponding composites (PLAJ-SFF and PLAJ-SBF), allowed a significantimprovement of the thermal stability and interfacial adhesion to be achieved. With the silane-treatedfibers, both tensile modulus and strength of the corresponding composites were improved. Whenadding Joncryl alone or in combination with silane, these mechanical properties improvedfurther.Closed loop recycling was performed after hygrothermal ageing to simulate the lifetime of thecomposites and before grinding and reprocessing.All composites without modified fibres exhibitedpull-out phenomena after recycling steps. The presence of Joncryl seemed efficient to maintain tensilestrength, but mainly for PLA/Flax composites. Only the silane/Joncryl combination allowed the tensilestrength to be conserved beyond 2 cycles of ageing and reprocessing

Influence of surface treatments and addition of a reactive agent on the properties of PLA/flax and PLA/bamboo composites

International audiencePolylactic acid (PLA) composites reinforced with 10 wt% of flax (FF) or bamboo (BF) fibers were prepared via an internal mixer and/or twin-screw extrusion. Alkali pretreated fibers were soaked in silane to improve adhesion between fibers and matrix. 0.8 wt% of Joncryl™, a grafted copolymer acting as PLA chain extender, was also used alone or in combination with silane treatment of fibers to improve interfacial adhesion. The influence of silane treatment and/or Joncryl on the composite materials on mechanical, thermal and thermomechanical properties of materials processed through injection molding was investigated. Improved adhesion of the fibers to the matrix was shown using a scanning electron microscope. Fourier Transform Infrared Spectroscopy indicated that chemical bonds were formed between the silane coupling agent and fibers. X-ray Photo-electron Spectroscopy confirmed that fibers and silane derivatives were effectively coupled. XPS also highlighted that silane coupling agent reacted in higher amounts on bamboo than flax fibers, probably due to a higher amount of lignin in the case of bamboo fibers. Thermogravimetric analyses indicated that silane-treated flax and bamboo increased the thermal stability of the corresponding composites (PLA-SFF and PLA-SFB) compared to non-treated fiber composites. The incorporation of Joncryl alone entailed a degradation of the thermal stability of the corresponding composites (PLAJ-FF and PLAJ-FB) but enhanced the PLA/fibers interfacial adhesion. The combination of Joncryl and silane treatment resulted in strong improvements of thermal stability and interfacial adhesion for the PLAJ-SFF and PLAJ-SBF composites. Increase in tensile moduli and decrease in tensile strengths with the incorporation of the pristine fibers were noted. For silane-treated fibers, the tensile modulus and the strength of the corresponding composites were improved when adding Joncryl alone or in combination with silane. From also rheological and molar weight measurements, it could be concluded that Joncryl acts both as PLA chain extender and coupling agent

How surface treatment and/or reactive agents allow closed loop recycling of PLA/Flax and PLA/Bamboo reinforced composites to be performed ?

International audiencePolylactic acid (PLA) composites with 10 wt% flax (FF) and bamboo (BF) fibers were prepared by meltmixing. Alkali pretreated fibers were treated by 3-aminopropyltriethoxysilane (APTES)[1-2]. A graftedcopolymer with epoxy groups (Joncryl ADR 4468[3], acting as chain extender was used alone or incombination with the silane treatment.The influence of silane and/or Joncryl on the compositematerials was investigated on the mechanical, thermal and thermomechanical properties of injectionmolding biocomposites. The adhesion of the fibres to the matrix was shown using SEM and FTIR. XPSindicated that chemical bonds were formed between silane and fibers. The combined used of Joncryland silane in the corresponding composites (PLAJ-SFF and PLAJ-SBF), allowed a significantimprovement of the thermal stability and interfacial adhesion to be achieved. With the silane-treatedfibers, both tensile modulus and strength of the corresponding composites were improved. Whenadding Joncryl alone or in combination with silane, these mechanical properties improvedfurther.Closed loop recycling was performed after hygrothermal ageing to simulate the lifetime of thecomposites and before grinding and reprocessing.All composites without modified fibres exhibitedpull-out phenomena after recycling steps. The presence of Joncryl seemed efficient to maintain tensilestrength, but mainly for PLA/Flax composites. Only the silane/Joncryl combination allowed the tensilestrength to be conserved beyond 2 cycles of ageing and reprocessing