Interfacial properties of PET and PET/starch polymers developed by air plasma processing.

The main goal of this paper was to determine interfacial properties of base untreated PET (polyethylene terephthalate) and starch modified PET as a function of time of air plasma processing. Air plasma was applied to improve the interfacial adhesion of starch to PET as an effect of oxidation and cross-linking changes. In turn, starch was used because the poor oxygen permeability of its layer can have a potential for the preservation of numerous food and pharmaceutical products. Wettability of the surfaces and work of adhesion on the basis of measurements of advancing and receding contact angles for the probe liquids on the PET plates base and covered with a starch film were obtained. The short plasma treatment was immediately followed by a sharp decrease of contact angle. Largely, in the course of longer plasma acting the contact angle of all liquids slightly increases due to the reorientation of polar groups towards the surface layer of polymer. Moreover, thermal and mechanical properties of base PET and those modified with air plasma were determined. Significant differences in elongation at break, but small differences in thermal stability and flexural properties of PET after plasma modification were observed. The starch film surface was characterized by FTIR measurements which confirm the contact angle results. Changes of time of plasma treatment and/or starch modification combination led to improvement of PET interfacial properties and biocompatibility. The obtained results expand the characteristics of PET/starch materials, which is of significant importance, particularly to formulate new starch coatings with controlled release and new biocompatible packaging PET/starch films with special properties. [ABSTRACT FROM AUTHOR]