Characterization of Environmentally Friendly Polymers by Inverse Gas Chromatography: II, Poly(3-hydroxybutyric acid)

Abstract

The surface thermodynamics of poly(3-hydroxybutyric acid) (PHBA) as a biodegradable polymer, was characterized using the inverse gas chromatography method. Gel permeation chromatography and differential scanning calorimetry method was also used to measure the molar mass, polydispersity, glass and melting temperatures. Twenty-seven solutes (solvents) with different families having a variety of chemical natures were used to measure the strength of the interaction forces of these solutes with PHBA. All these solutes showed an endothermic interactions which varied from one family to another. All families showed a chemical dependence on the interaction coefficients, a successful correction was used to eliminate the chemical dependence which resulted in exothermic interactions. Retention diagrams of all solvents showed no crystallinity occurred at the temperature range used. The molar heat of sorption of all solutes was measured from the retention diagrams ranged from − 19.41 for acetone to − 90.38 kJ/mol for cyclohexane. The dispersive component of the surface energy of PHBA was measured using alkanes which ranged from 24.42 mJ/m² at 80 °C to 13.94 mJ/m² at 120 °C. The decrease in surface energy attributed to the weakening of the surface at a higher temperature due to the melt and expansion of the surface.