Improved barrier properties of biodegradable PBAT films for packaging applications using EVOH: Morphology, permeability, biodegradation, and mechanical properties

Oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) of poly(butylene adipate-co-terephthalate) (PBAT) were improved by poly(ethylene-co-vinyl alcohol) (EVOH). PBAT/EVOH blends at varying amounts of EVOH were prepared through melt mixing and characterized by OTR, WVTR, SEM, DSC, FTIR, biodegradation in soil, hydrolytic degradation, and tensile tests. EVOH considerably improved the barrier properties of PBAT, example, 77% reduction in OTR and 40% reduction in WVTR at 50 wt% EVOH. Four models of Maxwell, Higuchi, Chiew & Glandt, and Levy were used to evaluate morphology and mechanism of transmission. A high elongation at break of 730% was observed for PBAT/EVOH blends up to 20 wt% EVOH but after that it severely dropped to 350% due to limited compatibility between the two polymers. Limited hydrogen bonding between PBAT and EVOH was observed by FTIR. EVOH accelerated the hydrolytic degradation of PBAT due to its high-water absorption capacity. This was not observed for biodegradation in soil suggesting that EVOH may retard microbial activity. After 540 h of hydrolytic degradation, the melting point and crystallization temperature of remaining PBAT increased by 5 and 10 & DEG;C due to more degradation in adipate rubbery domains and less degradation in terephthalate hard segments.

Automated summary

Poly(butylene adipate-co-terephthalate) (PBAT) was improved in terms of oxygen and water vapor barrier properties by incorporating poly(ethylene-co-vinyl alcohol) (EVOH). The addition of 50 wt% EVOH resulted in a 77% reduction in OTR and a 40% reduction in WVTR. The compatibility between PBAT and EVOH limited the elongation at break of the blends, with a decrease observed after 20 wt% EVOH. FTIR analysis confirmed limited hydrogen bonding between PBAT and EVOH. EVOH accelerated the hydrolytic degradation of PBAT but had no effect on biodegradation in soil.