Effect of food additives on the microstructure, mechanical and water transport properties of polyurethane films

The objective of this work is to study the effects of common food preservatives (BHT, α-tocopherol, EDTA-Na and potassium sorbate) on the morphological, mechanical and water transport properties of polyurethane (PU) as films or coatings. The influence of these additives on the polymer structure and the polymer-additive interaction was evaluated by using SAXS, FTIR and DSC. The addition of additives results either in the formation of aggregates or modification of the polymer microstructure, depending on the molecular size and nature of additive, i.e. number of polar groups, hydrophilicity, etc. The addition of BHT molecules seems to break the typical hard segments interactions in PUs, leading therefore to a good incorporation of the molecule in the polymer matrix, however, α-tocopherol does not incorporate onto the PU matrix leading to an evident phase separation and not affecting therefore the microrange of heterogeneities of the PU matrix. On the contrary, films doped with EDTA-Na or potassium sorbate showed important changes in both soft and hard segments domains. As consequence, the water transport properties were greatly affected by the incorporation of these food additives in the polymeric matrix. Films with potential antimicrobial or antioxidant activity were obtained, with a moderated decrease in the mechanical properties.