Enhancing the thermo-oxidative stability of PLA through the use of hybrid organic–inorganic coatings

PLA samples have been coated with organic–inorganic hybrid films containing SiO2as inorganic phase and two different types of organic phase PEO or PCL. Sol–gel solutions, spin coating deposition, and mild thermal treatments have been used to form thin protective coatings. Coated and uncoated PLA samples have been submitted to accelerated thermo-oxidative stresses at 120 °C in air up to about 400 h. The extent of the damage induced by this treatment has been evaluated by different techniques. Coated samples of both compositions are able to increase the resistance to thermo-oxidation of PLA as proved by the smaller reduction of molecular weight. This effect is probably deriving from the reduced oxygen permeability, as well as from the constrained outward diffusion and recombination of the cyclic oligomers produced by intramolecular transesterification reactions of polyester chains. Data so far collected underline also a long-term stability and adherence of the hybrid coatings during the entire aging process and hint at the possibility of using PLA in more demanding applications than that of packaging (i.e., electric industry, automotive field, or housewares). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43897.