I’ve been with Gougeon Brothers, Inc. since 1996, and 13 of those years were in the Order Entry Department where I talked to many interesting customers working on all sorts of projects. In 2007 I became a member of the Technical Department. Now, rather than giving product pricing to customers or advising them on the quantity they may need, I’m able to see how those products evolve from just a mere gleam in someone’s eye to a product we are proud to call our own. For me, being a part of this process means among many other things, handling our testing data. My role ranges from filing it all the way to building databases for the many tests we perform in-house. Continue reading
By Tom Pawlak and J.R. Watson
Spot prime metals with G/5 in place of slower drying paint primers for indoor applications prior to applying latex paints. Latex paint can be applied to G/5 about ten minutes after the epoxy is applied and while the epoxy is still soft. G/5 provides a thin barrier and prevents rust that otherwise forms in latex paint when it dries over bare steel.
Model railroad set builders create natural looking surfaces by applying a film of G/5 adhesive and then sprinkling small objects onto the surface while it is still uncured. These Continue reading
By J.R. Watson
Composites are a blend of resin (in this case mixed epoxy) and reinforcing fiber. Folks often ask, “How strong are they?” It is difficult to answer this question due to many variables including resin type, fiber type, fiber orientation, and resin/fiber ratio. To give a value for a laminate, we reduce the variables. Values shown in this article were done with test samples using WEST SYSTEM 105 Epoxy Resin®/206 Slow Hardener® at room temperature (70°F). Reinforcing fibers are Episize™ materials. Laminates made for the test had fibers oriented in one direction (unidirectional) and were laminated using Continue reading
At two-part adhesive in a convenient, self-metering cartridge for permanent, waterproof structural gap filling and gluing.
Six10® Adhesive gives you the strength and reliability of a two-part WEST SYSTEM epoxy with the convenience of a single part product. Six10 is dispensed with a standard caulking gun. Non-sagging Six10 bonds tenaciously to wood, metals, fiberglass and concrete. It cures in temperatures as low as 50°F. Working time is 42 minutes at 72°F. Cures to a solid in 5–6 hours and will take high loads in 24 hours. Cure time is faster at warm temperatures and Continue reading
By Jeff Wright
WEST SYSTEM® Six10 is a two-part, pre-thickened epoxy adhesive formulated with properties that make it perfect for many adhesive applications. Compared to other ready-to-dispense adhesives, its particular physical properties make it ideal for stitch and glue boat construction, fiberglass laminate repair and general bonding. This new formulation has a good balance between the elongation and toughness of G/flex® and the strength and stiffness of our 105 Resin-based epoxies. You can use it with as many materials as possible including wood, metals and composites. The long working time with fast thru-cure and unique shear thinning are additional characteristics formulated into Six10 that contribute to its ease of use. Continue reading
By J.R. Watson
The WEST SYSTEM® Six10 cartridge is comprised of the cartridge body, removable nose plug and a threaded retaining nut. A 600 static mixer is included with the cartridge. (It’s called a static mixer because it has no moving parts.) The cartridge fits into any standard caulk gun—manual, cordless or pneumatic—and allows simultaneous dispensing and mixing of the two-part epoxy. Manual caulking guns are graded by mechanical advantage (MA) in relation between the travel of the pistol grip and the plunger. When using he static mixer, resistance Continue reading
By now most of you know that we are the manufactures of WEST SYSTEM® Epoxy. But you may not know what is involved in the manufacturing and more specifically, the formulating of WEST SYSTEM. It’s not just slapping some chemicals together and then packaging it up into a pretty box. To date we have performed thousands of tests, generating thousands of test results. Continue reading
By Tom Pawlak and Jeff Wright
One of our goals for G/flex® was an ability to bond to a variety of plastics. This was an ambitious goal because plastics historically have been used as mold release surfaces for epoxy, allowing it to release from the plastic when cured. While developing G/flex, we tested adhesion to a number of plastics with a variety of surface prep methods. We discovered that some plastics need only be abraded for good adhesion to take place. Other plastics required additional surface prep involving a flame treatment to form dependable bonds. We discovered that a few plastics, like polypropylene and acrylic and their molecular cousins, are difficult to glue reliably no matter how we prepared the surfaces.
|Effectiveness of different surface preparation techniques on the adhesion of G/flex 655 Epoxy to various plastics|
|Plastic||Surface Prep||Tensile Adhesion (psi)
|ABS||Sand w/ 80-grit||1,854|
|Sand w/ 80-grit + Flame treat||1,813|
|Alcohol wipe + Flame treat||3,288|
|PVC||Sand w/ 80-grit||1,780|
|Sand w/ 80-grit + Flame treat||1,813|
|Alcohol wipe + Flame treat||2,081|
|Polyethylene||Sand w/ 80-grit||400|
|Sand w/ 80-grit + Flame treat||1,890|
|Alcohol wipe + Flame treat||2,312|
|Polycarbonate||Sand w/ 80-grit||1,870|
Adhesion with G/flex to properly prepared plastics (other than polypropylene and acrylic) varies from about 1,700 to 3,300 psi, depending on the plastic and the surface prep used. We tested these bonds with the Pneumatic Tensile Test Instrument (PATTI). The table above shows average adhesion achieved by G/flex 655 Epoxy to various plastics with different surface prep. In many cases the adhesion is not enough to exceed the strength of the plastic, but it is considerably better than bonds between plastic and other epoxy formulations. The chart also shows the advantage of flame treating (especially in the case of polyethylene) and the advantage of alcohol wiping over sanding before flame treating.
It takes more than good adhesion to make a successful repair. We all know how well epoxy bonds to plywood, but it is common practice to use a scarf joint or butt block instead of a straight butt joint. Plastic joints should be treated much like plywood joints. Our Fiberglass Boat Repair and Maintenance Manual discusses the importance of grinding the proper bevel when repairing a hole or major crack in a fiberglass skin. The shallow bevel angle reduces the stress concentration between the repair and the original surface, and increases the amount of surface area for adhesion. Reducing the stress concentration often helps minimize the chance of a peel failure, which is a common way adhesives can fail on plastic surfaces. Testing has demonstrated that the same technique improves bonding strength in plastic panels and reduces the chance of a repair failing in peel.
GLUING PLASTIC WITH G/FLEX
G/flex has been available since 2007. Enthusiasm for this toughened epoxy continues to run high within our company and in the field because of the unique properties that G/flex offers.
BEVEL AND ROUND THE EDGES
To repair 1/8″ to 1/4″ plastic, we recommend increasing the surface area along the joint by beveling and rounding the edges to be glued. This strategy is effective for repairing cracks in plastic canoes and kayaks. To test G/flex for this type repair, we simulated splits in the bottom of a thermal-formed plastic hull by edge gluing 1/8″ thick high-density polyethylene (HDPE) sheets.
By beveling and rounding the edges of the joint with a sharp object, sanding, and flame treating the surface with a propane torch, we effectively glued this plastic together. Figure 3 shows plastic being tested under deflection after repair. The article Repairing a Royalex™ Canoe with G/flex Epoxy used this same joint style.
The thickness of a material has an exponential effect on stiffness. When repairing small plastic boats, the relatively thin hull helps reduce the stress in the repair because the entire bottom or side will often deflect a significant amount under a small load. Although the plastic hull shell has deflected significantly, the overall stress in the material is low.
A thicker, and stiffer panel can generate much higher stresses as it deflects and put more stress on the edges of the glue joint. Repairing stiffer (thicker) plastic parts requires more attention to the possible cleavage and peeling loads.
Bonding surface area can be optimized with the use of fillets. Fillets are used to increase the surface area of the joint and reduce the stress concentration. The reduced stress concentration can help deal with off-axis loads which can cause the joint to cleave apart. We recently performed a tensile test on polyethylene butt joints by pulling apart samples with and without fillets (photos right). The samples that used fillets required almost 100% more force to pull apart.
REACHING OUR GOAL
Our formulating efforts were successful. We had an epoxy that would bond to plastics and we had a strategy for making plastic boat repairs.
As word of G/flex spread, we received lots of calls from canoe and kayak liveries. They had damaged boats made of molded plastic that needed to be repaired quickly because their season was about to begin. The damage ranged from normal wear and tear on the bottoms near the bow and stern, to cracks and splits that appeared randomly on the hulls.
The G/flex Epoxy kits come with an instructional brochure that explains a variety of repair techniques including plastic canoe and kayak repairs and the technique for flame treating (below). Repairing a Royalex™ Canoe with G/flex Epoxy demonstrates the effectiveness of those repair techniques on a severely cracked canoe made of ABS plastic.
By Tom Pawlak
NEW POSSIBILITIES FOR HDPE BOATS
D-ring pads are often attached to flexible surfaces with urethane adhesives to gain load carrying capacity where there otherwise wouldn’t be any. They are used on waterproof fabric cargo bags, heavy tarpaulins and inflatable boats. They are also sometimes used on the decks of canoes and kayaks to hold cargo in place on long trips. D-rings are not typically used on polyethylene canoes and kayaks because the urethane glues are not recommended for use on HDPE (high density polyethylene) plastic. We decided to experiment gluing D-ring pads with G/flex 655 to HDPE plastic with that end-use in mind. Continue reading
By Randy Zajac
It all started when I got a tech call from somebody asking if WEST SYSTEM® 105/206 would accept a nail pounded in, after it was cured, with no pilot hole. I confidently said that it would not work well and in most cases cause a fracture in the epoxy. Just for fun, I went out in the shop and tried it because even though every tech advisor agreed it wouldn’t work, nobody had ever actually done it. Well, we were right—the nail caused a “brittle” failure.
Then I saw a 1/8″ thick piece of cured G/flex 650 epoxy sitting on my work bench that I had Continue reading