Structural epoxy vs laminating resin

I am looking for some understanding of two basic materials to our hobby. Is laminating resin the same product as structural epoxy just not as viscous? I'm wondering if the laminating resin is used when I need it to run down into some small areas if it will have the same structural qualities.

Depends on the manufacturer, but usually not. Structural epoxy adhesive usually contain fillers and additives to thicken and modify it, whereas laminating epoxies do not.

Structural epoxies generally have better flex characteristics, and yes, with greater viscosity, they tend to stay where you apply them. Laminating epoxies rely on the properties of the substrate material for build up and to enhance their physical properties.

The basic epoxy resin, DGEBA (diglycydil ether of bisphenol A), is about as thick as cold molasses. Two brand names are DER331 and EPON 828. Some epoxy glues use DGEBA as the resin and any one of a number of curatives or curative mixtures. Usually 'fillers' are not included. The most common fillers are aluminum oxide, barium sulfate, calcium carbonate, aluminum metal, and a few others. You can tell when a filler has been added, the epoxy resin is no longer transparent. JB Weld has some kind of filler; it appears to be aluminum powder but might be something else.

Laminating epoxy is usually a mixture of DGEBA and a low-molecular-weight epoxide, a so-called reactive diluent. Unlike a solvent, the diluent reacts much the same as does DGEBA, but as it's much thinner it produces a thinner resin. The reactive diluent usually reacts faster than DGEBA, too.

Quiz on Friday.

Wow prfesser that was more than I could have hoped for. I was going to Google what is in resin but you took care of it. Thanks everybody. The comment about laminating epoxy depending on the substrate for strength makes lots of sense.

Speaknoevil said:

Structural epoxies generally have better flex characteristics, and yes, with greater viscosity, they tend to stay where you apply them. Laminating epoxies rely on the properties of the substrate material for build up and to enhance their physical properties.

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The flex part is very accurate. Normally rigidity is a plus when doing a lay-up because the flex is adjusted by the layers used in the substrate or fabric. I was ordering 2 gallons of resin every three months before i closed my shop simply because I used it for so many projects in the shop. I used my lay-up resin for many things including compression molds. These molds would take 60psi inside them and not fail. My point is you can indeed use a "resin" for structural applications with the correct fillers or additives.

Resins normally have a longer open window which means they end up with more cross linking of the molecules. This results in much better shear strength and a more rigid part.

rocketcharlie said:

I am looking for some understanding of two basic materials to our hobby. Is laminating resin the same product as structural epoxy just not as viscous? I'm wondering if the laminating resin is used when I need it to run down into some small areas if it will have the same structural qualities.

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You can use laminating epoxy in a structural application. Key is to start with a quality epoxy. Some are thin and some are thick (Not rocketpoxy thick). You can then use quality additives for them to be used in a structural capacity. I use rocketpoxy, proline4500, aeromarine 300/21 or 400/21 and have on hand large quantities of 1/8 chopped carbon, 1/4 chopped carbon, 1/4 chopped kevlar, milled kevlar, milled carbon fiber and milled s-glass. Plus large quantities of syringes for injecting etc. Just depends what I'm doing or the required result. I've used each epoxy with each additive over the years and have had excellent results.

The mention of JBWeld additives - IIRC, that's powdered iron, and calcium carbonate.

Gerald