Thermoplastic composites based on biopolymers and natural fibres

The objective of the present research is to utilise the advantages offered by renewable resources for the development of biodegradable composite materials. Two types of biocomposites using flax fibres as a reinforcement and poly[(R)-3-hydroxyalkanoates] (PHA) as a biodegradable polymer matrix were manufactured: First, natural-fibre-mat-reinforced thermoplastics (NMTs) using a compression moulding method and needle-punched nonwoven flax fibre mats and secondly, injection moulding compounds based on short flax fibres. The influence of fibre content and processing method on the tensile and impact properties of these composites was studied. Results indicated that the addition of (cheap) flax fibre to poly(3-hydroxybutyrate) (PHB) could be advantageous as far as cost-performance of these materials is concerned. For example, the addition of flax fibres to the relatively brittle PHB matrix offers the chance to obtain cheaper products together with improved toughness, while retaining biodegradability of the resulting polymer composites. Especially in the case of relatively long fibres as in the case of NMTs the improvement in impact resistance is significant. Regarding the influence of processing method it was observed that, with the exception of impact resistance, injection moulded samples possessed similar properties to NMT samples, indicating that for some applications injection moulding might be advantageous over NMT because of the more versatile production process.