The Best Fiberglass Glue: A Comprehensive Guide

When working with fiberglass and carbon fiber composites, choosing the right fiberglass glue is crucial for achieving strong, reliable bonds. This article will explore the best adhesives for performance bonding, including surface preparation techniques to ensure a successful bond.

Top Adhesives for Fiberglass and FRP Composites

Three of the adhesives I use most frequently for bonding carbon fiber and fiberglass reinforced polymers (FRP) are:

Hysol E120 HP

Viscosity similar to honey Bonds to a wide variety of substrates, including metals Not specifically noted for elasticity or thixotropy

ProSet ADV 175/276 and 176/276

These adhesives are known for their:

LV viscosity (viscous texture like Vaseline) Super toughened version with more elasticity (176/276) Thixotropic nature, hanging well on vertical surfaces without sagging Soft and easy to work with, spreading well

Lord Chemical’s T21

Thixotropic viscosity similar to peanut butter Excellent gap filling properties Harder cure than other adhesives mentioned Effort-intensive to mix and apply, especially in cold conditions

For bonding fiberglass to fiberglass or wood to fiberglass, ProSet 176/276 would be my top choice due to its performance. However, all of these adhesives are of excellent quality when used correctly.

Surface Preparation: The Key to Strong Bonds

Surface preparation is paramount for achieving strong bonds, especially with metals. If not adequately prepared, the bond may fail due to oxidation or contamination. Here are the steps for preparing surfaces:

Metal Surfaces

1. Remove Processing Oils: Clean the metal surface with warm soapy water to remove any processing oils.

2. Wire Brush: Use a steel brush on a Dremel tool to wire brush the surface, removing any oxide layer.

3. Ultrasonic Cleaning: Place the metal part in an ultrasonic cleaner with a mild soap solution for 10–20 minutes.

4. Final Cleaning: Dry the part completely and re-clean it with acetone (MEK or lacquer thinner) to ensure a fresh, dust-free surface.

FRP Surfaces

1. Remove Contaminants: Clean the surface with solvents or soap and water to remove any wax surfacing agents or contaminants.

2. Grinding: Sand the surface to provide a fresh clean surface.

3. Cleaning: Use clean paper towels and acetone, MEK, or lacquer thinner to ensure the surface is dust-free before bonding.

Best Adhesive for Hidden Fasteners and Axles

In my work on custom boarding ladders for mega yachts, I often use threaded inserts bonded into G10 blocks of fiberglass/epoxy. These blocks are then bonded to the inside of carbon fiber rails, requiring a strong, trusted bond.

Foam inserts are a common solution, but I prefer to use Lord T21 Fusor adhesive. Its viscosity holds the inserts in place and forms a very strong, solid bond when cured. This is particularly important for high-value custom projects like my ladders, which can cost up to $35,000.

Conclusion

Choosing the right fiberglass glue and ensuring proper surface preparation are key to achieving successful and long-lasting composite bonds. Take the time to follow these guidelines, and your projects will perform to your expectations, even in demanding environments.