Fast vs Slow Hardening Marine Epoxy Resin

Choosing the correct ratio mix for Marine Epoxy Resin helps ensure the Best Results

When you embark on a project using epoxy resin, in order to get optimal results, it is imperative to have a good idea of the amount of time you have to manipulate the polymer before it begins the thermosetting process and becomes unpliable. Once the epoxy/hardener bonding process begins; you should be finished with your resin application, shaping, filling and coating process well before the bonding and hardening/sealing procedure - so proper curing can take place to your satisfaction.

This is true of course for all epoxy resin products – not just marine grade. There are however, several reasons to select slow versus fast-setting epoxies, and the results vary as well. Slow-setting epoxy resin creates a stronger bond than fast-setting – but the difference may not be dramatic enough to be an issue depending upon the application. Slow-setting epoxy does of course, provide greater time to manipulate and shape the material - about 30 minutes - versus the 12 or so for fast-setting resin.

A variety of factors will affect epoxy resin curing time; hardener ratio, ambient temperature and the use of heating tools (heat guns and lamps) all play a part in epoxy resin’s transition from liquid to gel to solid. Epoxy resin will cure faster in a warmer than cooler environment - so in cooler conditions, using a fast hardener may be advisable – while the opposite may be warranted while working in warmer temperatures.

When it comes to marine repair and maintenance, noted boating repair expert and author on the subject, Don Casey has this to say from a column titled, ‘Polyester or Epoxy Resin,’

“However, when you are doing a repair, you need for the resin to also function as an adhesive — gluing the patch to the surrounding surface. Polyester is an adequate adhesive but not as good as epoxy. As a general rule, the tensile strength of a polyester bond will be around 20 percent weaker than the same bond made with epoxy. That makes epoxy resin usually the best choice for fiberglass repair work.” We agree!