Heterogeneity in the strength of interfacial bonds and the resultant synergism in promoting polyurethane/SBR adhesion strength

Abstract

Polymer adhesion and its evaluation are very important both from academic and industrial points of view. Adhesion phenomenon depends mainly on the strength of interfacial bonds and the deformability of adhering partners, which act as another energy absorbing term. Using a combination of acid-base interactions and a coupling agent at the interface of styrene-butadiene (SBR) -polyurethane system, a synergistic adhesion promotion was observed. The SBR surface was treated with an acidi ed aqueous solution of calcium hypochlorite to obtain polar groups, which can interact with the isocyanate groups of the polyurethane system. Aminopropyltriethoxysilane, a coupling agent, was also deposited at the SBR surface, after treating it with the aforementioned solution. The polar groups on the SBR apparently interact with the OH sites of the coupling agent at the surface and push the amino groups toward the polyurethane surface. This interesting nding, synergistic adhesion promotion, was attributed to the tortuous path for the crack growth at the interface, which was created by formation of the interfacial bonds with different strengths (heterogeneous bond strength). Furthermore, to obtain the highest synergistic effect, it seems that certain ratio of bonds with different strengths should be formed. The ratio itself depends on the deformability ratio of the adhering materials.

Practical work of crack growth and environmental stress cracking resistance of semicrystalline polymers

“…Sharif et al33 used the concept of heterogeneous bond strength to justify the observed synergism in promoting polyurethane/styrene‐butadiene rubber interfacial adhesion strength. The principle behind the concept was the tortuous path establishment of crack growth at the interface due to the formation of interfacial bonds with different strengths.…”

The role of joint viscoelastic function in the adhesion of low-density polyethylene to thermoplastic starch

“…Interfacial adhesion between two polymers is a complex phenomenon governed mainly by physicochemical and mechanical aspects [17]. Mutual inter-diffusion, interfacial physical and/or chemical bonding and compatibilizer localization at the interface could be mentioned as routes toward adhesion promotion [18,19].…”