How to Choose the Resin

Resin selection can vary from fabric compatibility, service conditions,fiberglass chopped strand mat and desired characteristics of the finished part. There are generally three types of thermosetting resin to consider when approaching your project: Epoxy, Vinyl Ester, and Polyester. Let’s take a look at each of the choices, their characteristics, and what they should be used for.

1. Epoxy Resin

For composite parts that demand the ultimate strength, fabricators will use an Epoxy Resin. In addition to increased strength properties, epoxies also generally outperform polyester and vinyl ester for dimensional stability and increased bonding with other materials.

Pros: 

Epoxy Resin, High Strength Properties, Can be used in vacuum infusion applications, Easy to handle, Medium viscosity

Cons: 

Cannot be used with chopped strand mat

Not UV stable. This must be paired with a top coat when exposed to UV rays

2. Polyester Resins

Polyester Resins are the most widely used resins in the composites industry. Polyester Resins are less expensive, offer some corrosion resistance, and are more forgiving than epoxies. The majority of all fiberglass parts are constructed using Polyester Resins because they are easy to use, fast curing, and tolerant of temperature and catalyst extremes. Fibre Glast carries two different types of Polyester Resins, each with their own strengths and uses.

POLYESTER MOLDING RESIN

Pros:

Inexpensive, Easy to handle, Rapid wet-out, High thixotropic index (product won’t run on vertical surfaces)

Cons:

lower physical properties compared to more expensive resins

ISOPHTHALIC POLYESTER RESIN

Pros:

Dimensionally stable (minimal shrinkage), resists post cure problems, can be used in food contact applications

Cons:

Slightly more expensive than general purpose polyester resins

3. Vinyl Ester Resin

Vinyl Ester Resin is considered a hybrid of polyester and epoxy—meaning its handling characteristics, properties, and price generally fall just between the other two. It is important to note that, Of the three, vinyl ester resin will provide the highest corrosion resistance, temperature resistance and elongation (toughness.) Because of this, they are typically used when high durability, thermal stability, and corrosion resistance is needed.

Pros:

Vinyl Ester Resin, Extremely tough, corrosion resistant, heat resistant

Cons:

Short shelf life (3 months)