Structural Adhesives

For joints that must carry loads, use structural adhesives, often two-part epoxies, which create a much stronger bond than an ordinary glue. For metal and fibreglass, a two-part epoxy is often the right choice. For working time, choose the 5-minute versions for small repairs or longer-setting ones for complex joints, as stated on the data sheets.

To repair boat hulls, panels and tanks in fibreglass, use a kit with resin, hardener and glass mat or cloth, laid up over the damaged area. The liquid or paste hardener sets the polyester resin and must be dosed as stated on the data sheet. Fibreglass filler fills imperfections before finishing. Prepare the surface by sanding and degreasing.

To fill cracks and fissures in concrete, use low-viscosity epoxy injection resins, which penetrate the cracks and restore the continuity of the material. For surfaces and pours, use a more viscous resin. The choice depends on the width of the crack, the temperature and the presence of moisture. Before injection, clean the crack and position the injection points as stated on the technical data sheet.

For bonding vehicle glass use one-part moisture-curing polyurethane adhesives, which react with the humidity in the air. On some surfaces a specific primer is needed, such as black polyurethane primer, to ensure adhesion to the glass and bodywork. Setting time and working temperature are stated on the data sheet. This work should be entrusted to trained personnel, as glass is a safety component.

Two-part epoxy putties fill holes, cracks and dents in metal, wood and cement, and are worked by hand like a paste. Once cured they can be sanded, drilled and painted. Mix the two components in the stated ratio until the colour is uniform. On metal surfaces, degrease and sand before application to improve adhesion.

A two-part adhesive cures only if the two components are dosed in the correct ratio: an excess of hardener or resin leaves soft or sticky areas. Working time, or pot life, is how long you have after mixing. Prepare only the quantity you can use, and never remix a product that has started to set. Measure carefully, using the supplied dosers or a scale.

Epoxy resins and polyurethane adhesives can cause skin or respiratory sensitisation. The isocyanates present in some polyurethanes are respiratory sensitisers. Once sensitised, even small amounts can trigger reactions. Use suitable gloves, goggles and a ventilated area, read the hazard statements on the safety data sheet and apply the chemical risk assessment under D.Lgs. 81/2008 (Italian Legislative Decree 81/2008 on workplace safety).