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Source for liquid thermosets: silicones, moldmaking urethanes, casting urethanes, polyester resins, epoxy.
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All products available in small quantity.

EP4117 General Purpose Polyester Laminating Resin



GENERAL DESCRIPTION:  EP4117 is a room temperature curing, rigid, translucent, polyester resin for use with fiberglass fabric. It is an air-inhibited resin so additional layers can be applied without sanding between layers.  Consequently, EP4117 is often called bonding resin or laminating resin. Successful applications include boat-building, auto body construction, mother mold production and other reinforced plastic parts by hand lay-up or chopper gun.


MIX RATIO: The gel time and cure time are both dependent on three parameters: (1) the percentage of MEK-P catalyst used; (2) the temperatures of all ingredients and the surrounding environment; (3) the mass concentration of the resin, i.e., a solid-cast shape vs. thin film. A good starting point, at 72°F, is 1-1/4 % catalyst by weight. This is equivalent to 10 drops catalyst per ounce of resin, or 1 teaspoon catalyst per pint of resin. This level will result in a 15 min pot life and a 24-hour cure. As temperatures rise above 72°F, decrease catalyst, and vice-versa. Polyester resins will not cure below 60°F. Experiment until the correct ratio is determined for your specific application. In general, mix what you can use in 10 minutes. Remember to always wear eye-protection when working with polyester resin and catalyst.


The strength of a fiberglass composite comes from the glass fibers. Thus, in making a strong fiberglass part it is crucial to use the correct amount of resin. Using a fiberglass roller will help saturate all the fabric with a minimum amount of resin. Please refer to our information sheet on making a fiberglass part for more detailed information.



The resultant room temperature cured plastic has these properties:


                                Viscosity                               650 cps

                                Specific Gravity                    1.11  (9.2 lbs./ gallon)

                                Tensile Strength                   10,000 psi

                                Compressive Strength         20,000 psi

                                Flexural Strength                  15,000 psi

                                Max. Use Temperature        180°F     


EP4117 is available in the following sizes:

                                Quart Kit                                2-1/4 lb

                                Gallon Kit                              9 lb

                                5 Gallon Kit                           45 lb

                                55 Gallon Drums                   500 lb


Qt, Gal, and 5 gallon sizes include the catalyst.  With drums, catalyst must be purchased separately by the Gallon.



Warning:  Uncured product may cause respiratory or skin irritation with possible sensitization. Use only with adequate ventilation. If skin contact occurs, wash thoroughly with soap and water. In case of eye contact, flood with water and call a physician. Use of gloves and face shield is recommended.  This product should not be used near food or where prolonged skin contact may occur.


Disclaimer:  This information is based on sources that we believe to be accurate. It is offered in good faith, but without guarantee, since conditions of use are beyond control. All  risk of use are assumed by the user.




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