Polyurethanes or epoxy adhesives work well with RIM polyurethane systems. The adhesion area of the joint should be at least three times the wall thickness. Bonds can have high strength in both tension and bending. Clean and roughen the adhesion areas to promote good bonding.
|Moderately priced||Some bonding materials have poor temperature resistance|
|Excellent toughness and flexibility||Sensitive to moisture both in cured and uncured state|
|Good flexibility at low temperatures||Two component mixing or single component toxicity|
|Excellent adhesives for a wide range of polyurethanes||Short pot life|
|One/two component, room temperature or heat-cute adhesives are available||Require special equipment to mix and dispense|
|Varying cure times|
Adhesives have been used to assemble composite components, such as inserts to assemblies and secondary brackets, and are sometimes used to join structural components. Bond reliability of adhesive joints is sometimes questioned for some composite applications.
Three adhesives are often used to bond composites: epoxies, acrylics, and urethanes. Epoxies are especially reliable when used with epoxy-based composites because they have similar flow characteristics. Careful preparation of the adhesion surfaces is essential to making a quality adhesive bond, but it varies depending on the adhesion and adhesive used.
Recommended preparation of many composite adhesion consists of a solvent wipe, to remove loose surface dirt and oil, and an abrading operation. Abrasion should be done carefully to avoid damaging composite surface fibers. In some cases, primer is required to coat the composite before applying the adhesive.
When bonding composites to metals, the metal substrate can be prepared by blasting with sand, grit, or metal oxides; abrading with a wire brush; and machining or scoring with cutting tools. Metal surfaces can also be prepared chemically. To protect freshly prepared metal surfaces from corrosion and contamination, adhesive should be applied as soon as possible.