Tributyl citrate as an effective plasticizer for biodegradable polymers: effect of the plasticizer on the free volume, transport and mechanical properties

Abstract

The effectiveness of tributyl citrate (TbC) as plasticizer for polylactide (PLLA) and poly(hydroxybutyrate) (PHB) was analyzed in order to improve the ductility of these polymers and make them good candidates for food packaging applications. Although the thermal and mechanical properties have been widely studied in literature the effect of the plasticizer on free volume and transport properties have not been deeply analyzed. The free volume was characterized by positron annihilation lifetime spectroscopy observing its linear increase with the TbC content. The permeability to water vapor, oxygen and carbon dioxide was determined and the obtained results were related to the changes on glass transition temperature, the crystallinity level of the samples and free volume. This work would allow a better understanding of the effect of the plasticizer on the barrier and mechanical properties of polymers allowing the development of competitive materials for packaging applications.