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Polyester Resin v. Epoxy Resin

January 24, 2018

 Epoxy resin makes a strong and durable tabletop.

We frequently get asked about the difference between epoxy resin and polyester resin. Often, people say “resin” without specifying which resin. It all depends on what your project is as to whether you would choose epoxy resin or polyester resin. Here’s a quick breakdown on the differences between epoxy resin and polyester resin.

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Epoxy Resin Characteristics:

  • Epoxy is extremely strong and has great flexural strength. Our 300/21 and 400/21 epoxy resins have a flexural strength of 17,500 psi. Our 300/11 and 400/11 epoxy resins have a flexural strength of 12,800 psi.
  • Epoxy has a great shelf life. While we guarantee our epoxy resins for 6 months, you can reasonably expect the epoxy to last at least a year when properly stored on the shelf.
  • You cannot vary the cure time of epoxy resin. Epoxy resin’s cure time is determined by the hardener and the ambient temperature. Our 300 resin with 21 hardener has a cure time of 24 hours at 70 F. Our 5 Minute Epoxy has a cure time of 60 minutes at 70 F. Adding more hardener will not make it cure more quickly! Too much hardener will actually make the cured epoxy rubbery. You can decrease the cure time by raising the ambient temperature around the epoxy resin. For every 10 F the temperature is raised above 70F, you can cut the cure time by 10%. However, don’t raise the temperature over 100 F.
  • A gallon of epoxy generally costs slightly more than polyester resin.
  • Epoxies like ours that are 100% solids are low to no VOC. They have little odor. Epoxy is also non-flammable.
  • Epoxy cures fully when applied as a thin film, making it ideal for adhesive applications.
  • Epoxy does not shrink when cured.
  • Epoxy is very resistant to wear, cracking, peeling, corrosion and damage from chemical and environmental degradation.
  • Once cured, epoxy is moisture resistant.
  • Epoxy is not, on its own, UV resistant. Some epoxies have a UV resistant additive added to them that works moderately well. However, the best way to ensure that your epoxy doesn’t yellow or breakdown from UV rays is to top coat it with clear UV resistant urethane. Then, you will have the strength and durability of the epoxy and the UV protection of the urethane.
  • Epoxy generally has a bonding strength of up to 2,000 psi.
  • Epoxy will not bond to polyethylene, polypropylene, EPDM, anodized aluminum, Teflon or Tedlar.

Polyester Resin Characteristics:

  • Polyester resin is brittle and prone to micro-cracking.
  • The shelf life of polyester resin is about 6 months – 1 year.
  • You can vary the cure time of polyester resin by adding more or less of MEKP catalyst.
  • Polyester resin generally costs slightly less than epoxy resin.
  • Polyester off-gases VOCs and has strong, flammable fumes.
  • Polyester resin does not cure well as a thin film, so it doesn’t work well as an adhesive.
  • The larger the pour, the more polyester resin shrinks when cured.
  • Polyester resin is UV resistant and does not need to be top coated to prevent yellowing or degradation from sunlight.
  • Once cured, polyester resin is water permeable, meaning water can pass through it eventually.
  • The bonding strength of polyester resin is generally less than 500 psi.
  • Polyester resin will not bond to epoxy resin.

Epoxy Resin Uses:

With its strength, glossy finish and durability, epoxy resin is ideal for things like:

  • Bar tops, table tops, and counter tops
  • Building and repairing wooden and fiberglass boats
  • Making fiberglass and carbon fiber parts
  • Coating wood and concrete
  • Casting small objects
  • Flooring
  • Potting electronics
  • Bonding wood, metal, concrete and many types of plastic
  • Sealing and patching wood that has dry rot
  • Pebble paving, and many more applications where thorough bonding, strength, glass-like finish and durability are required.

If you have any questions about what product would be best for your project, send us an email at [email protected] or give us a call, toll-free, Monday -Friday 9am- 4pm Pacific time at 877-342-8860. We are always happy to answer any questions you may have!

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