Epoxy and resins are adhesives commonly used in home, auto, aircraft and boat building projects. Epoxy is stronger, sets quickly and has a longer shelf life. Resin is less durable and sturdy but easy to tint, and is more often used for repairs and laminating.
Epoxy has great bonding strength. It sticks at 2,000 lbs. per square inch. Vinylester resins stick at 500 lbs. per square inch. Polyester resins stick at less than that.
Epoxy is very moisture resistant. Vinylester is more sensitive to moisture and temperature, which can affect how it sets. Polyester resin is the least resistant to moisture, the least tough and fractures easily.
Bonding Different Materials
You can use epoxy to bond different materials. Vinylester is less able to do this. Use polyester resin only when working with fiberglass. It's much less versatile.
Epoxy is the most expensive. One quart costs about $40 as of October 2009. Vinylester is about $25. Polyester is about $17, making it very popular despite its inferior qualities.
Resistance to Fatigue
Epoxy is more resistant to wearing, cracking and peeling. Vinylester is midrange, and polyester is the most fragile.