Improvement of barrier properties of bio-based polyester nanocomposite membranes by water-assisted extrusion

Hybrid membranes made of a biopolymer matrix poly(butylene succinate) (PBS) or poly(butylene succinate-co-butylene adipate) (PBSA) loaded with 5 wt% of native (CNa) or organo-modified (C30B) montmorillonites were successfully extruded using new extrusion conditions where liquid water was introduced into the extruder barrel to improve the nanofiller dispersion and exfoliation levels. The C30B incorporation in both matrices leads to the degradation of polymer chains and the reduction of the thermal stability while the CNa introduction combined with the water injection presents no effect on the polymer molecular weight and the thermal stability. The water-assisted extrusion process enables the increase in CNa dispersion and exfoliation levels in both matrices, which improves barrier properties to gases and water by tortuosity effects. In the case of C30B, the positive effect of dispersion induced by water injection was much less pronounced since C30B particles were already well dispersed and exfoliated in both matrices. The use of the water injection at high pressure during the extrusion process was found really efficient for native montmorillonite and so appears as a promising process for dispersing hydrophilic particles in polymers having a low hydrophilic character, without preliminary chemical modification of the fillers.