Biodegradable Poly(hydroxyalkanoate) Foams

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a member of the bacterial polyester family of poly(3-hydroxyalkanoates) (PHAs) known for its ability for enzymatic degradation and good mechanical properties.  The use of biodegradable polymers for producing sustainable materials has received increasing attention, and PHBV is an excellent candidate, shown to have similar properties to polypropylene (PP), known to be a tough and robust material.  Specifically, PHBV could be a useful material for construction materials such as insulation foam.  Current insulation foams are made primarily of polyurethane, polystyrene and polyethylene which are derived from non-renewable (petroleum) feedstock. 

However, processing of the PHBV into foam is limited by its low melt elongational viscosity and narrow thermal processing window.  Low melt elongational viscosity contributes to cell coalescence and collapse, resulting in undesirable high density foam.  The poor foamability of PHBV could be addressed via the addition of a nucleating agent and careful tuning of processing parameters.  Here, we discuss the potential use of orotic acid as a nucleating and a method for optimizing processing parameters based on solubility.