Effect of mechanical stretching and low amount of silica adding on gas transport properties of poly(butylene succinate-co-adipate) films

This work aimed at studying the influence of a post drawing process on the morphology and the gas permeability of a PBSA (Polybutylene succinate-co-adipate) film. Two films were studied, one of neat PBSA and one filled with 1%wt of silica. The influence of silica was also studied. Reference films of PBSA and PBSA + Si presented a spherulitic morphology despite a difference of spherulites sizes and long period. After stretching, this isotropic morphology changed to an oriented one, as shown by WAXS measurements. SAXS analysis revealed that stretching led to a lamellae organization in the stretching direction, with lamellae oriented perpendicular to the stretching direction. Thermal characterizations have shown that stretching did not modified the degree of crystallinity for both systems. The helium, carbon dioxide and oxygen permeability increased with stretching, mainly due to the orientation of crystalline lamellae, decreasing the diffusion path. Moreover, for PBSA + Si stretched films, small non-percolating voids were evidenced around the silica particles which could also make gas transport easier. Thus, for both systems, this increase in gas permeability happened in a different way.