8 - Characteristics of Adhesive Materials

Abstract

This chapter discusses the characteristics of several adhesive types. Alloyed or modified (Two-Polymer) adhesives are important as structural adhesives, especially in metal bonding. They are comprised of a thermosetting and a thermoplastic polymer, including certain elastomers. Anaerobic Adhesives/Sealants are acrylate acid diesters (polyester-acrylic). They are essentially monomeric thin liquids that polymerize to form a tough plastic bond when confined between closely fitting metal joints. Cyanoacrylate adhesives are marginally thermosetting. They form strong thermosetting bonds between many materials without heat or an added catalyst. They are particularly useful in bonding metal to nonmetal. Elastomeric adhesives are natural or synthetic rubber-based materials, usually with excellent peel strength but low shear strength. Their resiliency provides good fatigue and impact properties. Epoxy-polysulfide adhesives are products of reaction between an epoxy resin and liquid polysulfide polymer, usually catalyzed by an additional tertiary amine. Phenolformaldehyde adhesives, are condensation products of formaldehyde and a monohydric phenol. Phenolics are also among the lowest-cost adhesives and may be formulated as water dispersions, to allow penetration into the cell structure of wood that is important for the formation of permanent bonds. Water-based additives are prepared from materials that can be dispersed or dissolved only in water. Some of these materials are the basis of solvent-based adhesives and are the principal materials used for liquid adhesive formulations.