Glycerol-based additives of poly(3-hydroxybutyrate) films

Abstract

Glycerol (G), polyglycerols (PGs), glycerol triacetate (GTA), and glycerol tributyrate (GTB) were studied as additives of poly(3-hydroxybutyrate) (PHB). The effect of different concentrations (5–30%) of these compounds on microstructure and final properties of PHB films were evaluated. Microscopic studies revealed that samples with GTA and GTB presented uniform microstructure, meanwhile those containing G and PGs evidenced additives exudation. PHB exhibited a ring banded spherulitic structure and these additives, mainly G and PGs, induced modifications during polymer isothermal crystallization. All studied additives decreased PHB melting temperature, facilitating its thermal processability. GTA and GTB addition induced a reduction in PHB glass transition temperature, demonstrating their plasticizing effect. PHB films with GTA and GTB showed the best mechanical performance since they presented the highest deformation at break and the lowest maximum tensile strength, especially those with 30% GTB. Otherwise, G and PGs addition decreased films mechanical properties due to a prodegradative effect induced by them. GTB and PGs increased films water vapor permeability, meanwhile G and GTA decreased this barrier property.