Ultra-tough polylactic acid/poly(butylene adipate-co-terephthalate) blend for food packaging applications

In this research, a polymer blend of polylactic acid (PLA), poly (butylene adipate-co-terephthalate) (PBAT), and methylene diphenyl diisocyanate (MDI) compatibilizer was developed for food packaging applications. Considering the importance of flexibility in food packaging materials, the effect of different parameters on the elongation of the polymer blend was investigated and the conditions for producing a polymer blend with the highest elongation were predicted using response surface methodology (RSM). The RSM results showed that sample with 8 wt% PLA, 8 wt% PBAT, and 1 wt% MDI has the greatest elongation. Spectroscopy results verified that the chemical interaction is established between the isocyanate groups of MDI and the hydroxyl end groups of polymers. DSC showed that adding compatibilizer reduces the crystallinity by 67% and tensile test confirmed that adding compatibilizer increases the elongation by more than 110%. Biodegradation assay disclosed that compatibilizer does not have a negative effect on the biodegradation, and rheology analysis displayed that compatibilizer increases the melt strength and processability of the polymer blend. In summary, PLA/PBAT/MDI blend made in the present research with remarkable flexibility, high melt strength and acceptable biodegradability is a good choice for making food packaging.