Pressure-sensitive adhesive physical properties

Block copolymers are widely used industrially. In the solid and rubbery states they are used as thermoplastic elastomers, with applications such as impact modification, compatibilization and pressure-sensitive adhesion. In solution, their surfactant properties are exploited in foams, oil additives, solubilizers, thickeners and dispersion agents to name a few. Particularly useful reviews of applications of block copolymers in the solid state are contained in the two books edited by Goodman (1982,1985) and the review article by Riess etal. (1985). The applications of block copolymers in solution have been summarized by Schmolka (1991) and Nace (1996). This book is concerned with the physics underlying the practical applications of block copolymers. Both structural and dynamical properties are considered for melts, solids, dilute solutions and concentrated solutions. The book is organized such that each of these states is considered in a separate chapter. 

Kokubo, T., K. Sugibayashi, and Y. Morimoto. 1991. Diffusion of drug in acrylic-type pressure-sensitive adhesive matrices. I. Influence of physical property of the matrices on the drug diffusion. /. Contr. Rel. 17 69-78. 

Stabilization of Carboxylated Styrene Butadiene (X-SBR) Latices Carboxylated SBR latices are used as adhesives in applications where durability and flexibility are desired. Some of the major uses for X-SBR latex are in tufted carpet backing, paper coatings, wall and vinyl floor tile adhesives, and pressure-sensitive adhesives. Typically, discoloration is the first measure of the degradation of an X-SBR latex. Discoloration of a dried latex film can often be related to a loss of the physical properties and subsequently, to inferior performance in an adhesive formulation. Figure 9 illustrates the effects of adding an effective antioxidant system to an X-SBR latex on the level of discoloration as a result of static oven aging at 150°C (300°F). The addition of AO-4 alone... 

Because of the unique properties of pressure-sensitive adhesives, special tests not applicable to other types have been developed. While standard physical tests such as nonvolatile content, viscosity, and specific gravity are performed to ensure consistency of application, these tests do not predict adhesive performance. For pressure-sensitive adhesives, three critical performance characteristics are usually measured tack, peel, and shear strength. 

The particular category of Pressure-Sensitive Adhesives (PSA s) where the polymer exhibit visco-elastic properties able to develop adhesion during the bonding step as well as cohesion to resist to the debonding. No physical or chemical transformation of the adhesive is required to form the bonded joint. 

We may now make some quantitative estimates, using plausible numbers for the physical and mechanical properties that are involved. For a fibril drawn from the adhesive of a pressure-sensitive tape, we may assume an order of magnitude for rf, of about 0.01 mm, and ryy -5 rf, i.e. about 0.05 mm. We assume the substrate to be hard, strong and smooth, and that "physical" forces act across the interface, so that AG will be of the order of 100 ergs/cm = 0.10 j/m. The shear strength of the polymer, for a practical rate of elongation, may be about 1.0 X 10 N/m ( ) or about 140 psi. Then 0.004. 

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