[TOP 8 Difference] Polyester Vs Epoxy Resin

Polyester Vs Epoxy Resin

The first thing to note is that anytime a craftsman wants to use any resin form, they consider the kind of job they intend to carry out. This is a question that keeps recurring because many people do not understand the difference between epoxy and polyester resin.   If one is building a boat, the best resin is Polyester because of the fiberglass lay-up.

This is contrary to repairs where even though Polyester resin would still work, it is not as effective as epoxy, and in such cases, epoxy is more recommended. This is because it is 20% stronger than polyester resin and, as such, highly recommended for any repair work done with fiberglass.

It can be tricky to say that this is the exact difference, but this should not be a cause to worry because this article will review more on the differences.

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Let’s find out:

Resilience To Wearing Out

Since Epoxy is stronger than Polyester, it automatically turns out that it is resistant to wearing out, peeling, cracking, destruction from any chemical reaction, or any environmental effect. Polyester, on the other hand, is fragile and mainly used for the temporal fixing of surfaces.  But on the same note, Polyester is UV resistant, and one does not require to topcoat it. It is not affected by degradation from sunlight or yellowing.

Curing Time

The curing time for epoxy resin and polyester differs, but this depends on the temperatures they are exposed to. However, polyester takes a shorter time to cure under normal temperatures.

Epoxy resin, on the other hand, is determined by both the hardener used and the temperature. For instance, an epoxy of 300 resins with 21 hardeners can take 24 hours to cur if exposed to temperatures of about 70 degrees Fahrenheit. One can still decrease the curing time by raising the temperature to over 70 degrees Fahrenheit, but this should not go beyond 100 degrees Fahrenheit.

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Bonding Strength

Epoxy is known to have extremely strong bonding capabilities and exceptional flexural strength. From a practical point of view, it can hold at least 2,000lbs per square inch, as opposed to Polyester, which can hardly hold anything above 500 lbs.


Epoxy is way too high in terms of cost than polyester. It ranges between three to five times more than the price of polyester. This is because of its bonding strength and formulation, where it takes long without wearing out. DIY craftsmen consider using polyester resin mainly because they use it in jewelry making or minor repairs, which do not need much bonding strength. However, the bottom line lies with the user depending on the job requirements.


Epoxy has a little better pleasant smell than Polyester.  But on the other hand, it’s easier to set it up through the stinking rate, which puts one-off from using it.  Therefore, it’s recommended that whenever you are using any of the resins, always work on it from an area that is well-ventilated to avoid any health effects.

Moisture Resistance

So long as Epoxy is well cured, it has stronger moisture resistance than polyester. This makes it possible for some specific formulations to be applied even when the surface is underwater. On the other hand, polyester has less resistance to moisture, and since it is more absorbent to water, it fractures easily because of its flaccidity rate in it.

ALSO READ: How to Add Color to Epoxy Resin?


Epoxy is known to have a longer shelf life in comparison to other resins.  The average guarantee is six months, but in a real sense, if appropriately stored on the shelves, it can take more years than one would expect.

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On the other hand, the polyester resin becomes more fragile over time and does not last long on the shelves.


Epoxy does not shrink even after curing. This does not apply to polyester resin which is prone to shrink once it has cured, and since it is water permeable, once cured, water easily passes through it.

Also read: UV Resin vs Epoxy Resin – Which One Is Better for You?

Vinylester VS Polyester

Adhesives come in different names depending on their strength of each other.

Vinylester is an ungraded epoxy resin that is known to be stronger than normal Epoxy. It adds more power, adhesion, rigidity, and high resistance to chemicals and water. It’s preferable when the surface being applied to is a wood material.

This means that the cross bonding of the vinyl ester is of a higher nature than that of polyester adhesives and therefore meant for more strenuous applications.

Also read: What Is The Difference Between Epoxy and Resin?

Fiberglass Epoxy vs Polyester Resin

Fiberglass epoxy is an adhesive that is reinforced and woven using glass fibers. The plastic matrix model could be a thermoset polymer matrix that is centered on thermosetting polymers. An example of such is Epoxy. Polyester resin is that what is used for the fiberglass lay-up.  Its strength is not as strong as that of Epoxy and does not last long as well.

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Polyester Resin vs Epoxy Resin

The significant difference that exists between polyester resin and epoxy resin is its resistance to wearing. Whereas Epoxy is very strong and more resistant to wearing, peeling, corrosion, cracking, and even environmental degradation, Polyester is more fragile and mostly used for temporary bonding of surfaces.

Also read How To Polish Epoxy Resin?

Frequently Asked Questions

Q. Which is better, Epoxy resin or polyester resin?

A. Both of these are suitable adhesives, but then epoxy resin is stronger, thus more recommended for permanent applications and making it a better choice for fiberglass repairs. Polyester does well for less temporary applications.

Q. What is Polyester Resin Used for?

A. It’s mainly used in surfboards made from a polyurethane material where the fiberglass cloth is wrapped, primarily to give the board protection and have a stiff structure.

Q. What is a good substitute and a cheaper alternative to resin?

 A. One of the best-known substitutes for epoxy is concrete or hard plaster. These can act as tough casting materials, and they are cheaper than any resins on the market.  Artisans and contractors use concrete instead of resin when working with larger pieces whose cost would go too far from the expected.

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