Fully biodegradable composites: Use of poly-(butylene-succinate) as a matrix and to plasticize l-poly-(lactide)-flax blends

• Injected PBS–flax fiber composites were elaborated and mechanically tested.
• Efficient tensile or impact properties were shown due to the fiber individualization.
• In situ nanoindentation evidenced the interest of PBS to preserve the fiber integrity.
• Fully biodegradable PLLA–PBS–flax composites with optimized elongation were developed.

To take advantage of the mechanical performance of plant fibers and avoid their degradation, it is necessary to develop biocomposites by working on the least aggressive process conditions possible. The use of thermoplastic polymers with low processing temperatures is one possible way. In this study, tests were performed on poly-(butylene-succinate) (PBS) flax composite, extruded and injected at 140 °C. They have a good level of tensile or impact properties compared to poly-(propylene) (PP) or l-poly-(lactide) (PLLA) based biocomposites. Nanoindentation measurements were performed in situ on the composites. Despite the low Young's modulus of PBS, it was shown that the use of a moderate process temperature limits the downward stiffness of the flax cell walls. Finally, it was demonstrated that the PBS could be associated with PLLA for making flax fiber reinforced biocomposites. The introduction of PBS, with adjustable volume fractions, improves elongation at break and impacts on the behavior of PLLA–flax composites, whilst retaining high performance mechanical properties. Thus, it is possible to elaborate fully biodegradable composites with the desired mechanical properties.