Investigation of surface properties of biocomposite materials modified by corona plasma treatment

Studies aimed at determining the features of printing on biocomposite polymer materials were carried out. It has been found that the untreated composite films have a low adhesion strength at the composite film-paint interface, the surface tension did not exceed 28 mN/m, and the contact wetting angle was greater than 80 degrees. When the surface is activated by the "corona" discharge method, the adhesion properties appear to a greater extent, and with an increase in the processing stress of the "corona" discharge, the adhesion strength also increases. Thus, in a 25 kV surface treatment, the surface tension for the test composites was estimated to be above 40 mN/m and the contact wetting angle was less than 45 degrees. For BHA based on LDPE and TPC of various bases (corn, pea, rice), adhesion strength was evaluated in the range from 2.9 to 3.5 N/cm2, for PCM based on LDPE and ORD - 29 N/cm2. The result of this work is an increase in surface tension due to the appearance of polar groups on the surface of composite films, in particular oxygen-containing C-O and C = O, as confirmed by Fourier IR spectroscopy. Although the adhesion strength at the film-paint interface is increased when the surface of the composite films is activated, it has been observed that for LDPE-based BHC and thermoplastic starch, the adhesion properties are not constant and decrease over time. After two weeks, adhesion strength was evaluated, on average, 1.4 N/cm2. Most likely, BHCs do not transition to the electret state when the surface is activated by "corona" discharge, and external factors such as temperature and humidity act, as a result of which the number of polar groups on the surface decreases. On the contrary, a slight decrease in adhesion strength from 29 to 27 N/cm2 was observed for PCM based on LDPE and OPD, which is due to the chemical nature of the starting components.