How to Choose the Resin

Resin selection can vary from fabric compatibility, service conditions, 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)

A Simple Female Mold Construction with Fiberglass

Composite materials offer ability to be molded to complex shapes is perhaps the most popular. When a shape needs to be reproduced numerous times, it is most efficient to build a tool or mold within which the part can be fabricated. Molded parts emerge perfectly shaped every time and require little post-finishing work.

Molding or “stamping” has been used for years to shape metal products like car bodies, home appliances, and industrial fixtures. Metal stamping dies are cumbersome and cost thousands of dollars to produce. Only large companies can afford to build, operate, store, or even move these tools. Composite materials offer a cost effective way for anyone to make even large production runs of identical plastic parts in molds they can produce themselves.

Female molds or cavity molds offer numerous advantages for medium to large production runs. Finishing time is significantly reduced because every part emerges with a smooth outer surface.

PRODUCTS FOR MOLD CONSTRUCTION 

Duratec Gray Surfacing Primer

Modeling Clay

Parting Wax

PVA Release Film

Tooling Gel Coat

Chopped Strand Mat

Tooling Fabric

Woven Roving

10 oz Fabric

Polyester Molding Resin