Surface Properties of Modified Cardboard

Abstract

The influence of cardboard modification on the complex of its surface properties is studied. The cardboard surface properties were calculated based on the contact angle values of five different liquids. The samples absorbency was determined by the methods of full immersion and drop infusion. The effect of cardboard processing with polylactide and starch coatings on its wetting ability and absorbency was assessed. It was found that free surface energy changes when applying biodegradable polymers to cardboard; it decreases by approximately 37 % when applying polylactide coating, and it slightly increases (by approximately 3 %) when applying starch coating. The absorbency of completely immersed cardboard decreases in approximately 1.7 times when applying polylactide coating; this cardboard characteristic slightly increases (by approximately 6 %) when applying starch coating. Similar dependences were observed in the study of dripping absorbency of cardboard. Polylactide coating prevented the absorption of a drop of water, and the absorption time of the cardboard decreased during processing with starch coating. The changeability of properties of pulp and paper materials with the use of a unipolar corona discharge is shown. Imparting an electretretic state to pulp and paper materials was evaluated by the surface potential values, electrostatic field intensity, and effective surface electric charge density. The surface energy decreases by 20-25 % on average while processing with the permanent corona discharge of the initial samples of cardboard and cardboard modified with starch or polylactide. As a result, the absorbency of the modified cardboard with full immersion grows less than that of the original cardboard, and the absorption time of a drop of water increases in approximately 1.3 times.