Self-Adhesion (Autohesion) of Polyisobutylene. II

Abstract

Abstract In accordance with our concepts, the autohesion of polymers is caused by diffusion of segments of chain molecules from one layer into another layer of the same polymer brought into contact with the first. This conclusion was drawn by us from generally known facts and modern concepts concerning the nature of high-molecular substances. The present work represents an attempt to confirm experimentally the diffusional theory of autohesion. Polyisobutylene with a molecular weight of 150,000 was used to investigate autohesion. Polyisobutylene was chosen as the material for study because its molecules contain no double bonds. This renders them sufficiently stable in regard to oxidation at ordinary temperature. The strength of autohesion was characterized by the stress necessary to delaminate two laminated fabric strips treated before laminating with the polymer solution. For the preparation of splices subjected to delamination in determining the autohesion of polyisobutylene, use was made of strips of unsized technical cotton fabric with a smooth surface. The working length of the specimen was always 10 cm.; its width was usually 5 cm. The polyisobutylene was applied to the specimens in the form of 6.0–7.5 per cent solution. The polyisobutylene solution was made up in a low-boiling fraction of aviation gasoline, which left no dry residue upon evaporation. The quantity of polyisobutylene, in grams per square centimeter of specimen surface was established from the weight of the absolutely dry initial fabric and of the polymer coated material after drying.