Bio-composites for structural applications: Poly-l-lactide reinforced with long sisal fiber bundles

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The aim of the project was to prepare fully bio-based and bio-degradable composites for structural applications, ideally a competitor to structural timber. Composites of poly-L-lactide (PLLA) reinforced with sisal fibres were prepared. Matrix choice was obvious because of its glass transition temperature, reasonably good mechanical properties, low difference between glass and melting temperature important for processing heat energy consumption, bio-source and biodegradability. Sisal fibres were chosen for their low microfibril angle and were used in form of long fibre bundles aligned in the longitudinal axis of samples. It was important to modify compression moulding method to ensure proper fibre-to-matrix adhesion, even distribution of polymer among fibre bundles and prevent the polymer/fibre degradation during the processing. Resulting material outperformed wood (Douglas fir, Pine, Sitka spruce) and showed some quite impressive properties (high storage modulus, high flexural strength) outperforming the same class of materials (natural fibre reinforced polymers). .

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