Morphology and compressive behaviour of foams produced from thermoplastic protein

Novatein (R) is a patented thermoplastic biopolymer produced from denatured haemoglobin and serum albumin proteins, in blood meal. This material is biodegradable after processing, and when foamed could provide an alternative to expanded polystyrene and polyurethane for short-term applications such as packaging. This study aims to investigate the effect of processing temperature on foam density and morphology and how these properties effect compression behaviour. Unconstrained rapid expansion produced a range of foam densities, 0.28-0.45 g/cm(3), which were strongly dependant on temperature. The foams had compressive strengths between 200 and 600 kPa and an elastic moduli between 2.2 and 8 MPa. Under compression, high-density foams behaved like traditional plastic foams, while at low density they behaved more elastomeric. Models for open and closed cells successfully predicted the compression modulus and strength in the linear elastic region. The foams demonstrated a mixed mode morphology (open and closed cells) and an irregular distribution of cells, which explained the deviation from the models.