Category Archives: Materials Testing

fastener load path

More on Hardware Bonding

General considerations for epoxy bonded fasteners in wood

By Robert Monroe

With epoxy bonded fasteners, the idea is to balance the three parts, (fastener, epoxy and wood/hole) to obtain optimum performance. The key information needed is the tensile strength of the fastener, the shear strength of the epoxy and the withdrawal resistance of the wood or backing block. Continue reading

Panel Warping

By Tom Pawlak

CAUTION: Strip planked projects can warp to the point of being unusable if one side of the wood core is fiberglassed and the other side is left unsealed. Changes in wood moisture content on the unsealed side will cause the project to change shape. The potential for warping is greatest on thin wood-strip projects like canoes and kayaks. The thinner the planking, the greater the risk. Continue reading

Climbing Drum Peel Test for Adhesives

By Bruce Niederer

No matter how you use WEST SYSTEM epoxies, you expect us to back up the products and methods we recommend with solid data based on tests that simulate “real life” applications. To this end we began conducting the ASTM 1781-93 test method known as the Climbing Drum Peel for Adhesives. As expected, the results from this test method compliment the data we’ve already compiled using the PATTI (Pneumatic Adhesion Tensile Testing Instrument) meter. Continue reading

Effects of Cool Temperature on Adhesion

By Captain James R. Watson

Many shops are heated only while working on the project. Often a bonding application is allowed to cure after the furnace is turned down and the shop cools off overnight. The question arises, does this temporary suppression of the cure affect adhesion. Continue reading

Assessing Material Strength for Small Parts

By Captain James R. Watson

The appropriate laminate thickness for a particular application is difficult to come up with out of the blue. We have a “feel” for how strong something must be to suit our purposes. Our hands are fairly sensitive for detecting slight load increases, up to about 30 pounds. We can use them to evaluate a variety of materials. The only problem is, we don’t know the numerical equivalent of the pressure we’re applying. Continue reading

primer performance

House Paint Primer Performance

By Tom Pawlak

In the past, we’ve recommended applying an alkyd base primer over well cured, clean, and sanded epoxy surfaces. We wanted to know how this primer compared to the newer, fast drying primers now available. We recently did a study of various house paint primers over epoxy to support the growing number of customers using WEST SYSTEM epoxy for building restoration. Continue reading

Low-Tech Adhesion Testing

By Jim Derck

Before beginning a project, it’s a good idea to test the adhesion between epoxy and the materials to be used. Preliminary adhesion tests can help you choose the best materials and surface preparation methods. It can also help to avoid a surprise bonding failure.
At Gougeon Brothers, Inc. we use a Pneumatic Adhesion Tensile Testing Instrument (PATTI) for adhesion tests. After the PATTI test stud is bonded to the test surface, the stud is pulled in tension until it releases. The instrument gauge gives a precise pounds per square inch reading at failure. Continue reading

Minimizing Amine Blush

By Tom Pawlak with Tim Atkinson

I recently built a double-ended paddle for my kayak. The blades were made of thin mahogany plywood coated with epoxy. I had coated all the paddle parts with two coats of epoxy the day before, and overnight a thin oil-like film had formed on the surface of the epoxy. This is amine blush. To ensure a good bond between the blade and the shaft, I removed the blush with water, dulled the surface with an abrasive pad, and dried the surface with paper towels. I’m confident using my new kayak paddle because the mating surfaces of the shaft and blade were properly prepared prior to bonding. Continue reading