Study on the Influence of the Hardener over the Properties and Structure of Adhesives Based on Chloroprene Rubber

Polychloroprene solvent based contact adhesives are a substantial part in bonding the different substrates in the shoe, due to some peculiarities in the structure of chloroprene rubber. To increase the adhesion of the bonding of some materials, two-component polychloroprene adhesives are used. As a second component or hardener, polyisocyanate in solution is used. The aim of this study is to investigate the influence of the hardener (polyisocyanate) in the adhesive compositions based on chloroprene rubber on the properties and overmolecular structures during the formation of adhesive joint. It has been a comparison between the data from mechanical tests with data from microscopic studies of these adhesives to clarify the reasons for the formation of adhesive joint in the presence and absence of a hardener. Microscopic observations show that the crystalline texture of the adhesive composition improves in the presence of hardener. It also leads to increased cohesion forces within the adhesive film as it crosslinks the elastomeric macromolecules and creates a stronger bond between them, but in contrast, it weakens the adhesion forces between the adhesive and substrate. Mechanical tests confirm the conclusion of morphological studies on improving the cohesion and weakening the adhesion forces in the presence of hardener in the adhesive compositions.