Gas transport and characterization of poly(3 hydroxybutyrate) films

Renewable biodegradable films of poly(3-hydroxybutyrate) (PHB) were produced via thermo-compression and casting method (specimens 1 and 2). On specimens 1, gas permeability coefficients with CO2, O2, N2, and C2H4 gases were measured at 277 K, 288 K and 296 K. The physicochemical characteristics of PHB based on calorimetric, mechanical, and thermal examination were performed for both specimens. SEM and probe ESR technique showed the dramatic differences in their surface morphology and segmental motilities in polymer bulk. In the selected temperature range, the gas permeability ranking (Pi) for the thermo-compressed films is as follows: P(CO2) > P(O2) > P(N2) ≈ P(C2H4). The gas diffusion coefficients were considered to be dependent on the gas critical volume, in accordance with the semi-logarithmic function, consistent with a free volume model. The activation energies of permeability, diffusivity and spin probe rotation, as well as the apparent heat of sorption equilibrium, forecast the values of PHB barrier characteristics in the range of foodstuffs stored temperatures.