Thermal, mechanical and biodegradation studies of biofiller based poly-3-hydroxybutyrate biocomposites

Biodegradable poly-3-hydroxybutyrate [P(3HB)] and natural fillers - clay, peat, and birch wood flour - were used to prepare powdered composites to form pellets and granules. Pellets were produced by cold pressing of polymer and filler powder whereas granules were produced from the powders wetted with ethanol. Characterization techniques like IR spectroscopy, differential scanning calorimetry, X-ray analysis, mechanical analysis and electron microscopy were employed to study the properties of the initial P(3HB) and fillers and the composites. Analysis of the IR spectra of the composites showed the absence of chemical bonds between the components, i.e. the composites were physical mixtures. Young's moduli of the pellets prepared from initial materials varied considerably, and the highest value was obtained for P(3HB) pellets (350 MPa). Studies of biodegradation of composite pellets and granules in the soil for 35 days showed that the residual mass of the pellets had decreased to 68% for P(3HB); 56.4% for P(3HB)/peat; 67% for P(3HB)/wood flour, and 64% for P(3HB)/clay; granules exhibited a similar mass loss, residual mass of the granules of P(3HB) was 68.4%, P(3HB)/peat 46.4%; P(3HB)/wood flour 77%, and P(3HB)/clay 74%. This shows the significance of the material as an eco-friendly composite without sacrificing its mechanical properties.