Role of acid-base interfacial bonding in adhesion

TLDR

Macroscopic polymer adhesive strength is directly proportional to microscopic interfacial energy changes measured by Dupre's work of adhesion, and the strongest acid–base bonds are hydrogen bonds whose energies depend on donor acidity and acceptor basicity. Understanding the acid–base character of polymers and substrate or filler surface sites is important because interfacial acid–base bonding can appreciably increase work of adhesion and thus bond strength. The acidic or basic sites of polymers and inorganic substrates can be determined spectroscopically or calorimetrically, enabling prediction of adhesive bond strengths. Predictable enhancement of interfacial bonding is achieved by surface modification of inorganic surfaces to strengthen acid–base interactions.

Abstract

The strength of macroscopic adhesive bonds of polymers is known to be directly proportional to the microscopic exothermic interfacial energy changes of bond formation, as measured by Dupre's 'work of adhesion'. Since the work of adhesion can be very appreciably increased by interfacial acid-base bonding with concomitant increases in adhesive bond strength, it is important to understand the acid-base character of polymers and of the surface sites of substrates or of the reinforcing fillers of polymer composites. The best known acid-base bonds are the hydrogen bonds; these are typical of acid-base bonds, with interaction energies dependent on the acidity of the hydrogen donor and on the basicity of the hydrogen acceptor. The strengths of the acidic or basic sites of polymers and of inorganic substrates can be easily determined by spectroscopic or calorimetric methods, and from this information one can start to predict the strengths of adhesive bonds. An important application of the new knowledge of interfacial acid-base bonding is the predictable enhancement of interfacial bonding accomplished by surface modification of inorganic surfaces to enhance the interfacial acid-base interactions.