Mechanical properties, gas permeability and biodegradation mechanism of biobased poly(ester amide)s from 2,5-furandicarboxylic acid and amido diols for sustainable food packaging

The aim of this work was to evaluate the functional properties of a family of poly(ester amide)s (PEAs) for flexible food packaging applications. The polymers under study were previously synthesized via random copolymerization of furan 2,5-dicarboxylic acid (2,5-FDCA) with different amounts of 1,10-decanediol and an amido diol (AD 46). Poly(decamethylene furanoate) (PDF) and poly(ester amide) 46 (PEA 46) were the reference homopolymers. PEA copolymers were compression molded into films and subjected to WAXS, DSC, SEM analyses and water contact angle, mechanical, gas barrier tests. The results showed a remarkable improvement in the functional properties of PEAs compared to those of PDF, with a decrease up to about 50% of O2 and CO2 transmission rates, which were found to be comparable to those of commercial PET. The mechanical properties of PEAs were also improved in comparison with PDF because of the increased toughness and higher resistance to plastic deformation, paired with elongation at break up to 650%. In order to assess the effects of contact with food, the prepared films were treated with food simulants. Moreover, the films were stored in conditions of controlled temperature and humidity, chosen to replicate real scenarios of application involving aggressive environmental conditions. After contact with food simulant liquids, the materials became more rigid and less ductile, but their gas barrier properties remained superior to those of commercially widespread polyolefins. Finally, films were subjected to composting tests: the higher the amido diol content, the faster the degradation rate, which occurred via a mechanism of bulk hydrolysis, because of the higher hydrophilicity of amide groups. Overall, the results highlighted the potential of PEA copolymers for the production of biobased, sustainable, flexible food packaging.