Isophthalic Polyester Resin

4.9 star rating

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  • Item
  • Description
  • Price
  • Qty
  • 90/69-F
  • 90/69-F
    Quart w/ hardener
  • $54.95
  • 90/69-A
  • 90/69-A
    Gallon w/ hardener
  • $109.95
  • 90/69-AK
  • 90/69-AK
    Case (4 Gallons w/ hardener)
  • $399.95

  • 90-F
  • 90-F
    Quart (2 lbs)
  • $49.95
  • 90-A
  • 90-A
    Gallon (9 lbs)
  • $104.95
  • 90-B
  • 90-B
    5 Gallon Pail (40 lbs)

    Quantity Discounts

  • $399.95


Build Strength and Stability for Tough Parts

#90 Isophthalic Polyester is perfect for fabricating dimensionally stable polyester molds and corrosive service parts. It is often used as a durable repair material for tank linings. This Iso polyester resin offers fast wet-out in spray-up or hand laminates. When spraying, we recommend using a 18" nozzle. The 225 degree F service temperature resists exotherm and post cure problems. #90 Isophthalic Polyester Resin has better strength properties than a general purpose polyester resin, which allow it to be used in more demanding applications.

Properly fabricated parts may be used in food contact, electrical and military applications.

#90 Isopthalic Polyester resin is formulated for 1.25% MEKP catalyzation. This resin can be purchased alone or as part of a Resin and Hardener Kit.

#90/69-F kit contains (1) QUART RESIN, (1) #69-A.

#90/69-A kit contains (1) GAL RESIN, (2) #69-A.

#90/69-AK kit contains (4) GAL RESIN, (8) #69-A.

Isophthalic Polyester resin, also known as Isophthalic Polyester, is a type of thermosetting resin commonly used in composite materials. Here is some information about Isophthalic Polyester resin:

  1. Composition: Isophthalic Polyester resin is a combination of polyester resin and isophthalic acid. It is a thermosetting resin, which means it undergoes a chemical reaction when mixed with a catalyst and hardens or cures to a solid state.
  2. Properties: Isophthalic Polyester resin exhibits excellent mechanical properties, including high tensile strength, impact resistance, and dimensional stability. It also has good resistance to chemicals, moisture, and UV degradation, making it suitable for various applications. The chemical components are listed under FDA 177.2420 Title 21 making it usable in food and beverage contact applications.
  3. Application: Isophthalic Polyester is commonly used for applications that require superior strength, durability, and resistance to environmental conditions.
  4. Corrosion Resistance: Isophthalic Polyester resin offers enhanced corrosion resistance compared to standard orthophthalic polyester resin. It is often chosen for applications where the composite part will be exposed to corrosive environments, such as marine, chemical processing, and infrastructure industries.
  5. Versatility: Isophthalic Polyester resin can be used in various manufacturing processes, including hand lay-up, spray-up, filament winding, and infusion. It can be applied to create a range of composite products, such as tanks, pipes, boat hulls, automotive parts, and architectural components.
  6. Compatibility: Isophthalic Polyester resin is compatible with different reinforcement materials, such as fiberglass, carbon fiber, and aramid fibers like Kevlar. It can be used with various types of reinforcements to create composites with specific mechanical properties and performance characteristics.
  7. Curing: Isophthalic Polyester resin requires a catalyst or hardener to initiate the curing process. It will also need an air inhibitor like styrene wax or Duratec High gloss additive if used outside of a mold.

Here are some more details about Isophthalic Polyester resin:

  1. Improved Water Resistance: Isophthalic Polyester resin exhibits enhanced water resistance compared to orthophthalic polyester resin. This makes it suitable for applications where the composite part will be exposed to moisture, such as in marine environments or water storage tanks.
  2. Chemical Resistance: Isophthalic Polyester resin has good resistance to a wide range of chemicals, including acids, alkalis, and solvents. It is often selected for applications that require resistance to chemical corrosion or exposure to aggressive substances.
  3. Heat Resistance: Isophthalic Polyester resin has moderate heat resistance.
  4. Low Shrinkage: Isophthalic Polyester resin typically exhibits low shrinkage during the curing process. This can help minimize the development of internal stresses in the composite, resulting in improved dimensional stability and reduced likelihood of cracking or warping.
  5. Gel Time: The gel time of Isophthalic Polyester resin refers to the time it takes for the resin to reach a gel-like consistency after the catalyst is added. The gel time can vary depending on the specific resin formulation and ambient conditions. It is an important consideration for process control and workability during composite fabrication.
  6. UV Stability: Isophthalic Polyester resin has moderate resistance to UV degradation. However, prolonged exposure to direct sunlight may lead to color fading and surface degradation over time. To enhance UV resistance, the use of UV-resistant coatings or topcoats is recommended for composite parts exposed to outdoor or UV-rich environments.
  7. Styrene Emission: Isophthalic Polyester resin, like other polyester resins, contains styrene, which is a volatile organic compound (VOC) with a distinct odor. Proper ventilation and personal protective equipment (PPE) should be used when working with Isophthalic Polyester resin to minimize styrene exposure and ensure a safe working environment.
  8. Storage and Shelf Life: Isophthalic Polyester resin should be stored in a cool and dry place, away from direct sunlight and heat sources. It typically has a limited shelf life and may undergo changes in viscosity or other properties over time.

As with any composite material, it is crucial to follow the guidelines, safety precautions, and processing recommendations specific to the Isophthalic Polyester resin being used. This ensures optimal performance, proper handling, and desired results in the final composite product.

warning WARNING: This product can expose you to chemicals including Styrene which is known to the State of California to cause cancer. For more information go to


Isophthalic Polyester Resin quart (#90-F) and gallon (#90-A) units and kits can be shipped via standard ground service without hazard charges within the 48 contiguous United States. 5-gallon quantity (#90-B) is considered hazardous (flammable) and will be subject to a hazard charge if shipped by standard ground. All sizes of #90 (quart, gallon, and 5-gallon) will be subject to a hazard charge if shipped by air. Please see our Hazardous Shipping Chart for more information about hazard fees. We will consolidate items whenever possible to minimize these fees.


Isophthalic Molding Resin This resin is available in a variety of sizes that include: One quart (#90-F) One gallon (#90-A) A five-gallon pail (#90-B) One drum (#90-DRUM) *Quantity discounts are available on the five-gallon pail only, when four or more units are ordered at one time. This resin can be purchased as part of a kit that includes MEKP catalyst. You should purchase the kit unless you already have hardener in your workshop. The kits include: One quart of resin, with one 1 oz. bottle of hardener (#90/69-F) One gallon of resin, with two 1 oz. bottles of hardener (#90/69-A) One case of four gallons, with eight 1 oz. bottles of hardener (#90/69-AK)


4.9 star rating

Iso resin

Feb 2, 2024  |  By Greg Geren

Most excellent product

No title

Aug 1, 2022  |  By Edward

Fast delivery, well packaged, great product...

Precision racecars

Mar 31, 2021  |  By Joe Gambino

Service is great. Prices are fair. Great company. I will be using for all my comp needs
Precision racecars
Mar 31, 2021  |  By Joe Gambino
Service is great. Prices are fair. Great company. I will be using for all my comp needs

Mold building
Mar 3, 2018  |  By CLIFF DE LA CERDA
This product works great, as advertised. I used this resin for building my canoe mold. Can be used in cooler temps, highly recommended.

Iso polyester resin
Feb 11, 2018  |  By michael sherman
This was one of my smallest orders, using this to repair CenTek exhaust collector on a customers boat. Have used over 30 gallons of FibreGlast supplied resins in the past, always impressed by the high quality, ease of wet out and the tech support. Always feel bad for the people I see in the marine chain store,purchasing that jelly like, almost unusable stuff off the shelf.

Easy for this novice to use
Dec 14, 2016  |  By Jim
I bought the quart size for a small project. I like that the container is suited for pouring; other products I've used came in quart "paint-style" containers with a lip that makes it messy to pour, or dip. Instructions on the can include the amount of catalyst needed for 1 ounce of resin, which is what I sometimes need for small projects. Set time was as expected for the temperature.

Great product/Difficult online ordering
Aug 20, 2015  |  By Kate W
Your service is great, your product (isophthalic resin) was exactly what I needed and it came quickly. Your online purchasing was difficult, however. It is apparently not possible to purchase something and have it sent to an address other than the billing address - at least I couldn't figure out how to do it. I had to have the resin shipped to the account because her name was on the credit card - a minor but unnecessary inconvenience. The second time I tried to order from you, I couldn't figure out why your site wouldn't let me complete my order. Fortunately, your sales person was pleasant and efficient.

Polyester resins
May 29, 2015  |  By Phillip P
I was pleased to return to my favorite composite website and order my preferred resin for use in building giant scale model RC aircraft. You used to have a name for glass cloth compatible with epoxy and/or polyester resins. What happened to this important distinction?

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