Techniques for increasing the thermal stability of poly[(R)-3-hydroxybutyrate] recovered by digestion methods

Abstract This work deals with the thermal stability of poly[(R)-3-hydroxybutyrate] (PHB) obtained by different isolation methods. PHB was recovered from bacteria by digestion with three different reagents (acid, base, surfactant) and by chloroform extraction as a reference. Thermal stability of the samples was investigated by differential scanning calorimetry, isothermal degradation with hot press, and gel permeation chromatography and was compared with the stability of commercially available PHB. PHBs recovered by digestion with alkaline reagents were found to be thermally unstable, compared to the extracted polymer and the commercially available one. Two different techniques for stabilization of PHB obtained by digestion methods were tested wash with acid solution or addition of carboxylic acid or anhydride before heating. Both methods proved to significantly increase the thermal stability.