Crystal formation of polyisobutylene induced at metallic interface

Polyisobutylene (PIB) is used as a nonpolar adhesive, but its mechanism of adhesion is still under discussion. Because the adhesion process of PIB requires no chemical reactions, the changes of physical properties induced at the interface play important roles in the mechanisms of the adhesion. PIB is known as an amorphous polymer, but can be crystallized by external stimulus such as stretching. Differential scanning calorimetry was carried out for thin films of PIB contacting with silver to investigate the interfacial properties and their contribution to the mechanism of adhesion. An endothermic peak appeared at the temperature which has been reported to be the melting point of PIB crystals, and this peak became clearer by thinning the PIB film. This thermal behavior can be explained by the crystal formation of PIB at the metallic interface. The formation of the crystals of PIB may contribute the good adhesive behavior of PIB. The rubbery amorphous phase of PIB with the glass transition temperature lower than room temperature can be spread on the surface, and the induced rigid crystalline phase prevent PIB from flowing. Copyright © 2011 John Wiley & Sons, Ltd.