Effect of recycling on mechanical behaviour of biocompostable flax/poly(l-lactide) composites

Abstract

The biocompostability of natural fibre-reinforced biopolymers, also known as biocomposites, makes them attractive alternative to glass fibre-reinforced petrochemical polymers. The aim of this work is to study the capacity of flax/PLLA (poly(l-lactide)) biocomposite (20% and 30% fibres by weight) to be recycled. Mechanical properties were evaluated initially, and shown to be similar to those of glass/PP and superior to hemp/PP and sisal/PP composites. Then after repeated injection cycles tensile properties were shown to be conserved until the third cycle. Matrix degradation and fibre aspect ratio were followed using molecular weight measurements, thermal and rheological analyses, image analysis of sections and SEM fractography. These techniques revealed a lower molecular weight, lowering of glass transition temperature, reduction of fibre length, and separation of fibre bundles with injection cycles. Nevertheless, the property retention after three cycles under extreme recycling conditions (100% recycling with no added virgin polymer) indicate the promising recyclability of these materials.

Disposal Options of Bamboo Fabric-Reinforced Poly(Lactic) Acid Composites for Sustainable Packaging: Biodegradability and Recyclability

“…Moreover, the shortened fiber length might result in more strain concentrations and a higher risk of debonding [27]. This occurrence can be observed in the ESEM micrographs of composites.…”

“…A decrease of tensile properties and an increase of flexural properties were observed in recycled BF-PLA composite, when compared to the BF-PLA composite (initial material). The loss of tensile properties might be due to the alteration of composite matrices during the recycling process, including granulation, extrusion and injection [27]. Alternatively, the increased flexural properties (strength and modulus) might be because of shortened and dispersed bamboo fabric yarn in the composites during injection molding.…”

“…It can be clearly seen that the elongation at break of recycled BF-PLA composites decreased compared to BF-PLA composite, consequently reducing the impact strength of the recycled BF-PLA composites. However, recycled material is always mixed with virgin material in an industrial situation [27]. Due to the reduction in the length and diameter of the yarn, fiber pull out can occur.…”

Influence of reprocessing on fibre length distribution, tensile strength and impact strength of injection moulded cellulose fibre-reinforced polylactide (PLA) composites

“…In the case where fibre bundles are opened to smaller bundles or single fibres the aspect ratio may increase during reprocessing, in contrast to single glass fibres which have a decreasing aspect ratio. The lower decreasing aspect ratio of flax fibres leads to a lower decrease of the composites' tensile strength after reprocessing when compared to glass fibre-reinforced composites [9]. Moreover the interface quality influences the fibre breakage.…”

“…Some approaches exist for the mechanical reprocessing of composites and the further processing by injection moulding, e.g. for flax fibre-reinforced PP [4,8], flax fibre-reinforced polylactide (PLA) [9], hemp fibre-reinforced PP [2,3], sisal fibre-reinforced PP [2,3], wood fibre-reinforced PP [4,10], wood fibrereinforced high density polyethylene (HD-PE) [11] or alfa fibre-reinforced polyvinylchloride (PVC) [12]. A decrease in fibre length during reprocessing was found for all cited studies.…”