Guide to Marine Epoxy Resin

Epoxy resin has been used in the marine industry for decades. It was extremely expensive and only used on high-performance boats, but over the years it has become more affordable and is now used more extensively. 

Marine epoxy resin fiberglass boat

Epoxy resin remains the most expensive marine resin type because it provides the strongest adhesion and bond. It’s also compatible with the widest range of materials, and effectively bonds dissimilar materials to form incredibly strong structures. Marine epoxy resin can be used for just about anything, from boat building to repairing, reinforcing, fabricating and attaching components. 

Epoxy Resin Bonding and Strength

Epoxy adheres to and bonds with just about any material, including wood, metals and cured polyester and vinylester laminates. It’s suitable for building and repairing fiberglass, wooden and metal boats. 

Epoxy resin fiberglass boat repair

Marine epoxy resin makes it possible to combine different materials, such as adding fabricated fiberglass stringers to a wooden hull. Cured epoxy has a far higher tensile strength than polyester or vinyl ester, so a bond made with epoxy offers more structural reliability, making it the best option for repair work.

Epoxy has two distinct drawbacks: poor resistance to UV rays, and that gelcoat won’t adhere to it. This means epoxy is not the ideal resin to use as an external top surface. Epoxy can be painted or varnished to protect it from UV rays, but if gelcoat is to be applied after the repair work is completed, polyester or vinylester resins may be better options. 

Fiberglass boat damage epoxy resin

When curing, marine epoxy resins shrink less than polyester or vinylester resins. So if a large area is being repaired, epoxy is the best option. With less shrinkage, the repaired area won’t be put under additional stress, which is important if the area being repaired is a deck.

Mixing Epoxy Resin

Unlike polyester and vinylester resins, which use catalysts to cure and harden, epoxy resin uses a hardener to enable the curing process. 

West System 105 marine epoxy resin

West System 206 epoxy hardener

Different hardeners can be used to speed up or slow down the curing process, but the ratio of resin to hardener must be precise. Epoxy is also more sensitive to temperature and humidity when curing than other marine resins. So larger jobs may require the work be carried out within a workshop or similar enclosed area.

As with all marine resins, once epoxy resin has been mixed with the hardener, the curing process can’t be stopped. The mixed epoxy must be used or discarded. Epoxy resin has the longest shelf life of all the marine resins, and can be stored for several years before use, so it can be bought in bulk and then used when the need arises. The higher cost of epoxy resin is perhaps the only reason it’s not as popular as polyester resin

 

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