Morphology and permeability of bio-based poly(butylene adipate-co-terephthalate) (PBAT), poly(butylene succinate) (PBS) and linear low-density polyethylene (LLDPE) blend films control shelf-life of packaged bread

Abstract

Poly(butylene adipate-co-terephthalate) (PBAT), poly(butylene succinate) (PBS) and linear low-density polyethylene (LLDPE) were blended to produce bio-based packaging via blown-film extrusion. Blend ratios modified morphology, crystallinity and relaxation temperatures (T α ) of the films. Binary mixtures caused phase separation and non-homogeneous fibrous microstructures of immiscible polymers. Bio-based blend films containing LLDPE (LLDPE/PBAT and LLDPE/PBS) gave less homogeneous structures than PBAT/PBS films. The formation of oriented fibrous networks subsequently controlled mechanical and barrier properties of the blend films. LLDPE blending modified C=O carbonyl groups in PBAT and PBS, forming voids in topographic images indicating incompatibility. PBAT and PBS blends showed good compatibility and adhesion of polymer interface, causing smooth and compact structures with minimal surface roughness. Incorporation of PBAT and PBS sharply reduced crystallinity of LLDPE/PBAT and LLDPE/PBS films. LLDPE/PBAT blends had lower T α than neat PBAT and LLDPE, while T α of PBAT/PBS blends proportionally decreased at increasing PBS which indicated diverse polymer miscibility and molecular mobility. Water vapor permeability (WVP) and oxygen permeability (OP) fitted with polynomial and exponential equations, respectively and depended on blend ratios. Films containing higher PBS had combined higher WVP and lower OP, delaying fungal growth in packaged bread due to dehydration. Ratios of PBAT, PBS and LLDPE blend films clearly affected mold growth and crumb hardness during storage. Regardless of film components, the firmness of bread crumbs increased linearly with package WVP. Conversely, mold growth had insignificant correlation with OP. Moisture loss from bread crumbs due to high WVP showed dominant effects on microbial growth. Blending PBAT and PBS modified the morphology and permeability of bio-based films and increased the shelf-life of packaged bread. • Systematic investigations for packaging properties in bio-based PBAT/PBS/PE blends. • FTIR intensity ratios effectively monitor bonding and morphology modifications. • H 2 O and O 2 permeability in PBAT/PBS/PE blends fitted to cubic and exponential model. • Hardness of packaged bread linearly increased with water vapor permeability. • Water vapor permeability majorly affected mold growth and increasing crumb hardness.