Polyester vs Vinyl Ester Resins

Vinyl Ester vs Polyester Resin



Poly or Vinyl? The resin you choose can have a big impact on your project. When working with composites, there are a wealth of materials and tools to work from, and each of them have their strengths and weaknesses. Having a lot of choices is great, but only when you are informed enough to make the informed choice. So how do you know which ones are right for you?

This week’s blog will cover Polyester and Vinyl Ester Resins. What each of these are, their strengths and weaknesses and information on what each might potentially be used for. We’ll also cover resins in general, and how they are used.

When combined with a reinforcement fabric, resins serve two primary purposes. First, the resin will hold the reinforcement fabric together while helping it conform to the desired shape. Without a hardened resin to provide shape, reinforcement fabrics are shapeless and can be easily separated.

Second, resins help transfer mechanical loads from individual fibers or fiber bundles across the entire fabric. While the reinforcement fibers provide the primary strength for a laminate, the role of the resins, transferring that load across an array of fibers, is also paramount to the overall strength and stability of the part.

Polyester Resins

Polyester Resins

Polyester resins are far and away the most common resins you will find within the composite industry. Polyester resins are naturally UV resistant, are generally viewed as easy to use, fast curing, tolerant of temperature and catalyst variations, and are less expensive than the alternatives.

Of course, Polyester resin does have some drawbacks. For one, you will not see the corrosion resistance in Polyester Resin that you will in Vinyl Ester, nor will you see the level of strength and durability you’d get from an Epoxy Resin. Thin coats of polyester resin also have a tendency to become tacky when exposed to air. This can be countered by adding a Styrene Wax to your resin when you know you’ll be working with thin coats. (Note, the wax will rise to the surface after use, and will need to be sanded off before your next layer can be applied.)

Being the most common type of resin in the industry, it is difficult to narrow down its applications. That said, you can expect to find polyester resins used in the marine industry, used for boat hulls and other applications, as well as general part fabrication, automotive applications, and for low-cost molds.

Fibre Glast carries two types of polyester resin, our #77 Polyester Molding Resin, as well as the #90 Isopthalic Polyester Resin.

Vinyl Ester Resins

Vinyl Ester Resins

Vinyl Ester resins are often considered a cross between the common polyester resin, and the more expensive epoxy resin. While this is somewhat oversimplified, it does help convey the qualities of the resin in laymen terms. Price wise, Vinyl ester will fall between polyester resin and epoxy, as well as with most physical and handling properties. Where vinyl ester truly exceeds is in its corrosion, and heat resistance, along with elongation (toughness.)

Due to this, vinyl ester resins are typically used when high durability, thermal stability, and extremely high corrosion resistance is needed. This can include the rebuilding of chemical storage tanks. Increasingly, the marine industry is exploiting these properties by using vinyl ester resins to produce and repair fiberglass boat hulls.

A drawback of Vinyl Ester resins is its limited shelf life. Many vinyl ester resins only have a three month shelf life, meaning that fabricators will typically want to order this on a project to project basis, instead of keeping a supply on hand.

For Vinyl Ester Resins, Fibre Glast has the #1110 Vinyl Ester Resin.

Polyester vs Vinyl Ester resin

So, how do the two weigh up against each other? By far the favorite for every day projects is the Polyester Resin. It’s ease in handling and affordable price make it a quick pick for most fabricators. However, in parts that have a high risk of corrosion, Vinyl ester is highly recommended. For those looking to stock up on resins for future projects, Polyester resin is much preferred, due to the short shelf life of vinyl ester.

Other questions? Let us know your thoughts in the comment section below. For more information on laminate resins, check out Fibre Glast’s White Paper on Resins, where we cover everything you need to know on Polyester, Vinyl Ester, and Epoxy Resin. Be sure to check out our Facebook, and follow us on twitter @Fibreglast for more information the composites industry.

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