Degradation of Poly(3‐Hydroxybutyrate) by Potassium Phosphate

Poly(3‐hydroxybutyrate) (PHB) is a biodegradable polymer that represents a potential replacement for some traditional plastics. The properties of PHB are impacted by many variables including its molecular weight. There are many applications that can be fulfilled by low molecular weight PHB (LMWPHB). We have investigated the use of potassium phosphate (K 2 HPO 4 ) as a catalyst for degrading PHB. Potassium phosphate was demonstrated to degrade the polymer in a concentration‐dependent manner. Low concentrations (0.2%) of K 2 HPO 4 decreased the thermal stability of the polymer and rapidly reduced the molecular weight. Comparisons to related chemicals (potassium sulfate, potassium chloride, calcium phosphate, and sodium phosphate) demonstrated that the K 2 HPO 4 had the greatest effect on thermostability. Low amounts of K 2 HPO 4 , but not other salts, led to a decrease in the crystallization temperature and bimodal melting behavior, indicative of the formation of smaller crystallites. This is the first report of the use of K 2 HPO 4 to convert PHB into lower molecular weight species.