Protein Plastic Foams

The development of protein-based biopolymers has been driven by the increasing global demand for polymer products, the need for sustainable practice within this industry and the availability of low cost by-products, such as high protein content meals. The continuing development of new and existing protein-based biopolymers will enable these materials to help supplement the increasing global demand for polymer products and to develop new markets with their niche applications. To date various compositions of protein-based biopolymers have been successfully used to produce injection moulded articles, films and foams. Biopolymers typically display poor foaming behavior and commonly produce foams with irregular morphology and high densities. Protein-based biopolymers are no exception, therefore it is important to fully understand how the foaming mechanisms of bubble nucleation, growth and stabilization are affected by the inherently different properties of these materials. This chapter aims to review the production of stable protein-based foams for use in applications such as cushioning, insulation and packaging through a variety of methods. The review specifically focuses on the production of protein-based foams through thermosetting, the emerging role of proteins as a renewable substitute in polyurethane production and the application of thermoplastic foam technologies to protein-based thermoplastics, with an emphasis on batch and extrusion foaming methods. The similarities and differences between the production of traditional foams and those produced from proteins are highlighted here. Discussion of foam morphologies, properties and processing conditions is also included. Overall, this chapter intends to provide the reader with a greater understanding of the existing research and the current challenges associated with the production of protein-based thermoplastic and thermoset foams.

Keywords: Batch foaming, Extrusion foaming, Polyurethane foams, Protein biopolymers, Protein foams, Thermoplastic proteins, Thermoset foams.