Choosing your resin or mastic

Epoxy or polyester?

Epoxy resin is more expensive but surpasses polyester in terms of waterproofing and mechanical strength for structural repairs.

However, polyester resin may be sufficient for many applications, but do not apply it to an epoxy laminated substrate under penalty of having a poor structural and/or aesthetic result.

What is its purpose?

Laminating fabrics such as fiberglass, carbon fiber, Kevlar; sealing; bonding; making sealants with added fillers (silica, microballoons, carbon powder, etc.)

Choosing your resin or mastic

Finishing

Use a finishing putty of the same type as the resin. To paint over epoxy, use a two-component paint, or a primer if using a gelcoat finish.

A single-component or direct application of gelcoat will suffice on polyester.

Choosing your resin or mastic

What temperature?

Ambient temperature affects polymerization: work above 15°C, or buy winter resin with the appropriate hardener (polymerization from 5°C)

Choosing your resin or mastic

Price

Epoxy resin is more expensive than polyester resin, and the price can quickly escalate for large areas. Expect to pay around thirty euros for 1.5 kg of epoxy, compared to around fifteen euros for polyester.

Small repair kits are affordable and avoid the waste of large containers that harden over time.