The role of molecular diffusion in the adhesion of elastomers

Abstract

Butyl rubber (polyisobutylene‐co‐isoprene) mixed with polyisobutylene was crosslinked to yield elastomeric macromolecular networks containing dissolved linear macromolecules. Adhesion of these materials to themselves (self‐adhesion) and to an inert substrate was investigated over a wide range of peel rates and test temperatures. Greatly enhanced self‐adhesion was found when linear polyisobutylene molecules of high molecular weight were present, but the strength of adhesion to a rigid inert substrate was hardly affected. The enhancement of self‐adhesion is attributed to interdiffusion of polyisobutylene molecules. It was greatest at intermediate peel rates and temperatures, becoming insignificant at extremely low rates, probably because the diffusing species can then migrate readily, and at high effective rates of peel when the polymer approaches the glassy state and the strength of adhesion is high in all cases. A transition to somewhat lower levels of adhesion at relatively high rates of peel is tentatively ascribed to the onset of molecular fracture in place of pullout. The presence of large amounts of low‐molecular‐weight polyisobutylene (M̄v = 50,000 g/mol) increased the level of self‐adhesion and of adhesion to an inert substrate to a similar degree, over a broad range of peel rates. This effect is attributed primarily to enhanced viscous losses in the elastomeric layer during separation. Application of these results to crack and weld‐line healing in glassy plastics is discussed.

Efficacy of Novel Nanoclay in Autohesive Tack of Brominated Isobutylene-co-p-Methylstyrene (BIMS) Rubber

“…The D value of sample B has been estimated as 9.1 × 10 −21 m 2 /s. This value shows some cor- [36]. From Table 3 it is seen that the self-diffusion value of BIMS rubber decreases with the addition of nanoclay, which is ascribed to the restriction in molecular mobility [longer terminal relaxation time (τ te )] due to the nanoclay reinforcement.…”

Hot tack of metallocene catalyzed polyethylene and low-density polyethylene blend

“…Similar findings have been observed by other researchers. 5,6 Other studies have been conducted to understand why mPE has the higher hot tack at lower sealing temperatures and how it affects the hot tack of its blends. In one, the higher hot tack of mPE film at lower temperatures is attributed to its unique molecular structure and melting behaviors.…”

Adhesives

“…Another basis for obtaining a strong joint between such materials for polymer-polymer adhesion is the phenomenon of interdiffusion (12)(13)(14)(15). In many cases, interdiffusion between polymers is difficult because of poor entropy gain.…”