WEST SYSTEM TECHNICAL MANUAL & PRODUCT GUIDE
Published by Gougeon Brothers, Inc., Bay City, MI, USA
Copyright 1994 GBI
Thank you for considering WEST SYSTEM® Brand Epoxy for your building and repair needs. This publication is designed to provide basic procedures for epoxy use and help you become familiar with WEST SYSTEM products.
The OVERVIEW is a quick look at how the basic WEST SYSTEM products- resin, hardeners, fillers and additives are combined for coating, bonding and fairing applications.
The TECHNICAL MANUAL section provides information about safety, handling and the basic techniques that will help you use these products effectively and take full advantage of WEST SYSTEM epoxy's versatility. Understanding these basic techniques will allow you to select and combine WEST SYSTEM products, tailoring them to your exact repair and construction needs. They are a fundamental part of the detailed repair and building procedures described in WEST SYSTEM instructional publications and videos.
The PRODUCT GUIDE section gives you complete descriptions of WEST SYSTEM products, including selection and coverage guides to help you choose the most appropriate products for your project.
For additional technical, product, or safety information contact:
WEST SYSTEM Brand Epoxy cures to a high-strength plastic solid at room temperatures, by mixing specific proportions of liquid epoxy resin and hardener.
By using a simple "cookbook" approach you can tailor the handling characteristics and the physical properties of the cured epoxy to suit your working conditions and specific coating or bonding application.
1. Start with 105 Epoxy Resin, the basic ingredient of all WEST SYSTEM epoxy compounds.
2. Control the cure time or adjust to the working temperature or working time required with one of four specially formulated WEST SYSTEM hardeners.
3. Adjust the strength, weight, texture, sandability and color of the cured epoxy with one of six WEST SYSTEM fillers. Adjust the viscosity of the resin/hardener mixture by the amount of filler added. Or, provide specific coating properties with WEST SYSTEM additives.
This section is designed to help you safely handle WEST SYSTEM epoxy products and provide the basic techniques used in most repair and building operations. Refer to the Product Guide following this section for specific product descriptions, and coverage and selection information.
GOUGEON BROTHERS, INC., P.O. Box 908, Bay City, MI 48707-0908 USA
(517) 684-7286, Fax (517) 684-1374
Mixing the epoxy resin and hardener together begins a chemical reaction that gradually changes the combined ingredients from a liquid to a solid. Careful measuring and thorough mixing are essential for the reaction to occur. Whether the resin/hardener mixture is applied as a coating or modified with fillers or additives, observing the following procedures will assure a controlled and thorough chemical transition to a high-strength epoxy solid.
Dispense WEST SYSTEM resin and hardener into a clean plastic, metal or paper container. Don't use glass or foam containers because of the potential danger from exothermic heat build-up. REMEMBER! Always wear gloves and eye protection when handling epoxy.
Most problems related to curing of the epoxy can be traced to the wrong ratio of resin and hardener. To simplify metering, Gougeon Brothers, Inc. recommends using calibrated WEST SYSTEM Mini Pumps to dispense the resin and hardener.
301 Mini Pumps and 303 Special Ratio Mini Pumps deliver the proper working ratio with ONE FULL PUMP STROKE OF RESIN FOR EACH ONE FULL PUMP STROKE OF HARDENER. Verify the proper ratio according to the instructions that come with the pumps, before you use the first mixture on a project. Re-check the ratio anytime you experience problems with curing.
To measure 105 Resin and 205 or 206 Hardener by weight or volume, combine five parts resin with one part hardener.
To measure 105 Resin and 207 or 209 Hardener by volume, combine three parts resin with one part hardener. Refer to the hardener containers for 207 and 209 weight ratios.
IMPORTANT! Do not attempt to control cure time by altering the hardener ratio.
Mixing epoxy with error-free results involves three separate steps:
CAUTION! Heat is generated by the chemical reaction that cures epoxy. A plastic mixing cup full of mixed epoxy will generate enough heat to melt the cup, if left to stand for its full pot life. If a pot of mixed epoxy begins to exotherm (heat up), quickly move it outdoors. Avoid breathing the fumes. Do not dispose of the mixture until it has cured and cooled.
- Dispense the proper proportions of the resin and hardener into a mixing pot. Begin with a small batch if you are unfamiliar with the pot life or coverage of the epoxy.
- Stir the two ingredients together thoroughly with a wooden mixing stick (1 to 2 minutes is recommended). Scrape the sides and bottom of the pot as you mix. Use the flat end of the mixing stick to reach the inside corner of the pot.
- Add fillers, additives or pigments if required, after thoroughly mixing resin and hardener. If you are going to be using the mixture out of a roller pan, mix it thoroughly in a mixing pot before transferring it to the roller pan. Do not use a power mixer unless you thoroughly scrape the sides and corners of the mixing pot while mixing.
The transition period of an epoxy mixture from a liquid to a solid is generally labeled the "cure time." It can be divided into three phases–open time or wet lay-up time (liquid state), initial cure (gel state) and final cure (solid state). The speed of the reaction (and the length of these phases and the total cure time) varies relative to the ambient temperature and mass of curing epoxy (Figure 1).
- Open time
Open time or wet lay-up time describes the working life of the epoxy mixture. It is the portion of the cure time, after thorough mixing, that the resin/hardener mixture will remain in a liquid state and be workable or suitable for application. The end of the open time (wet lay-up time) marks the last opportunity to apply clamping pressure to a lay-up or assembly and obtain a dependable bond.
- Initial cure phase
The open time is over when the mixture passes into an initial or partial cure phase (sometimes called the green stage) and has reached a gel state. At this point the epoxy will no longer feel sticky, but you will still be able to dent it with your thumb nail. It will be hard enough to be shaped with files or planes, but too soft to dry sand. Because the mixture is only partially cured, a new application of epoxy will still chemically link with it, so the surface may still be bonded to or recoated without sanding.
- Final cure phase
In the final cure phase, the epoxy mixture will have cured to a solid state and will allow dry sanding and shaping. You should not be able to dent it with your thumbnail. At this point the epoxy will have reached about 90% of its ultimate strength, so clamps can be removed. The epoxy will continue to cure over the next several days at room temperature. A new application of epoxy will not chemically link to it, so the surface of the epoxy must be sanded before recoating to achieve a mechanical, secondary bond.
Controlling cure time
The selection of one hardener over another is often based on the hardeners "pot life," rather than its overall cure time.
Pot life is a term used to compare the relative rate of reaction of various resin hardener combinations. By definition, it is the amount of time a given mass of mixed resin and hardener will remain in the liquid state at a specific temperature. For specification purposes, we determine the pot life of an individual resin/hardener based on a 100g-mass mixture in a standard shaped container, at 72°F (22°C). Pot life is equivalent to the open time or working life of a resin/hardener combination only under these conditions. Several important factors affect the actual length of an epoxy mixture's open time and overall cure time:
Regardless of what steps are taken to control the cure time, thorough planning of the application and assembly will allow you to make maximum use of the working life of the mixture.
- Type of hardener
Each resin/hardener combination will go through the same cure phases, but at different rates. The product guide and container labels describe hardener pot lives and cure times. Choose the hardener that gives you adequate working time for the job you are doing at the temperature and conditions you are working under. 205(fast) and 206 Slow Hardener may also be mixed to provide a custom blend with an intermediate open and overall cure time. It is critical, however, that the proper 5 part resin to 1 part hardener ratio is maintained. Do not mix 205 or 206 (5-to-1 ratio) Hardeners with 207 or 209 (3-to-1 ratio) Hardeners.
- Mixed quantity
Mixing resin and hardener together creates an exothermic or heat producing reaction. The larger the quantity of mixed epoxy, the more heat generated. And, more heat results in a shorter open time and overall cure time. Smaller batches generate less heat than larger batches and will provide longer open and overall cure times. Therefore, a thicker joint or layer of epoxy will cure sooner than a thin layer.
- Container shape
Heat generated by a given quantity of resin/hardener mixture can also be dissipated by pouring the mixture into a container with greater surface area (a roller pan, for example), thereby extending the open time. Since the epoxy will cure at a faster rate while it's in the mixing pot, the sooner the mixture is transferred or applied (after through mixing), the more of the mixture's useful open time will be available for coating, lay-up or assembly.
Heat can be applied or removed from the epoxy to shorten or extend open and cure times. A hot air gun, hair dryer or heat lamp can be used to warm the resin and hardener before mixing or after the epoxy is applied, reducing its cure time. Note that heating epoxy that has not reached its initial cure will lower its viscosity, allowing the epoxy to more easily run or sag on vertical surfaces. In addition, heating a porous material (soft wood or low density core material) that has been coated with epoxy may cause the material to "out-gas." Air within the porous material will expand and pass from the material, forming bubbles in the epoxy coating. This can be a concern if you desire a clear finish. Never heat the epoxy over 120°F (49°C).
A fan can be used to draw heat from the epoxy and extend its cure time.
Adding fillers and additives
Throughout this manual, we may refer to epoxy or resin/hardener mixture, meaning mixed resin and hardener without fillers added; and thickened mixture, meaning resin/hardener with either high-density or low-density fillers added. Fillers are used to thicken the basic resin/hardener mixture for specific applications, generally bonding or fairing.
The thickness of a mixture is controlled by the amount of filler added. Figure 2 gives you a general guide to the differences between unthickened epoxy and the three most commonly used consistencies.
Always add fillers in a two-step process:
- Mix the desired quantity of resin and hardener thoroughly before adding fillers. Begin with a small batch.
- Stir in small handfuls or scoops of the appropriate filler until the desired consistency is reached. Be sure all of the filler is thoroughly blended before. Spread the mixture to a thin layer to extend working time.
Although additives are blended with the mixed epoxy in the same two-step process as fillers, they are not designed to thicken the epoxy. Additives are used in smaller quantities to give the epoxy additional physical properties when used as a coating. Follow the mixing instructions on the individual additive containers.
Scrape up as much excess or spilled material as possible with a squeegee, sharpened mixing stick or a putty knife. Then wipe up residue with a solvent dampened clean rag or paper towel. Use acetone or toluene (lacquer thinner) to remove 105 Resin or mixed epoxy. 855 Cleaning Solution or vinegar can be used if a solvent is unavailable. The longer mixed epoxy is allowed to cure, the harder it is to clean up. Use hot water to remove spilled hardener.
If you get resin, hardener or uncured epoxy on your skin, wash with waterless skin cleaner followed by soap and water.
WARNING! Do not use solvents directly on your skin. Read directions and precautions on solvent containers before using.
The following basic techniques are common to most repair or building projects, regardless of the type of structure or material you are working with.
Whether you are bonding, laminating, filleting, fairing or applying fabrics, the success of the application depends not only on the strength of the epoxy, but also on how well the epoxy adheres to the surface to which it is being applied. Unless you are bonding to partially cured epoxy, the strength of the bond relies on the epoxy's ability to mechanically "key" into the surface. That is why the following three steps of surface preparation are a critical part of any secondary bonding operation:
Surfaces must be free of any contaminants such as grease, oil, wax or mold release. Clean contaminated surfaces with a silicone and wax remover such as DuPont Prep-Sol™ 3919S. Acetone or lacquer thinner works well on many contaminants. Wipe the surface with plain white paper towels before the solvent dries. Clean surfaces before sanding to avoid sanding the contaminant into the surface. CAUTION! Follow all safety precautions when working with solvents.
Removing amine blush
Special preparation may be required for epoxy surfaces. Amine blush can appear as a wax-like film on cured epoxy surfaces. It is a by-product of the epoxy curing process and may begin to form during the initial cure phase. The blush is water soluble and can easily be removed, but can clog sandpaper and inhibit subsequent bonding if not removed. To remove the blush, wash the surface with clean water and an abrasive pad. We recommend 3-M Scotch-brite™ 7447 General Purpose Hand Pads. Dry the surface with plain white paper towels to remove the dissolved blush before it dries on the surface. After washing with the abrasive pad, the surface should appear dull. Sand any remaining glossy areas with 80-grit sandpaper. Wet-sanding the surface will also remove the amine blush. If a release fabric is applied over the surface of fresh epoxy, all amine blush will be removed when the release fabric is peeled from the cured epoxy. Epoxy surfaces that have not fully cured may be bonded to or coated with epoxy without washing or sanding. Allow epoxy surfaces to cure fully, then wash and sand before applying coatings other than epoxy (paints, bottom paints, varnishes, gelcoats, etc.).
For good adhesion, all bonding surfaces must be as dry as possible. If necessary, accelerate drying by warming the bonding surface with hot air guns, hair dryers or heat lamps. Use fans to move the air in confined or enclosed spaces. Watch for condensation when working outdoors or whenever the temperature of the work environment changes.
Sand hardwoods and non-porous surfaces thoroughly to abrade the surface. 80-grit aluminum oxide paper will provide a good texture for the epoxy to "key" into. Be sure the surface to be bonded is solid. Remove any flaking, chalking, blistering, or old coating before sanding. Remove all dust after sanding.
This section refers to two types of bonding. Single-step bonding is occasionally used when joints have minimal loads and excess absorption into porous surfaces is not a problem. Two-step bonding is the preferred method for most situations because it promotes maximum epoxy penetration into the bonding surface and prevents resin-starved joints.
Before mixing epoxy, check all parts to be bonded for proper fit and surface preparation (See Surface Preparation), gather all the clamps and tools necessary for the operation, and cover any areas that need protection from spills.
Apply a straight resin/hardener mixture (without fillers) to the surfaces to be joined (Figure 3). This is called "wetting-out" the surface. The resin/hardener mixture may be applied with a disposable brush for small or tight areas, or a foam roller for larger areas. A large horizontal area can also be wet out by spreading the resin/hardener mixture evenly over the surface with a plastic squeegee. You may proceed with step two immediately, or any time before the wet-out coat reaches final cure.
- Applying thickened epoxy
Modify the resin/hardener mixture by stirring in the appropriate filler until it becomes thick enough to bridge any gaps between the mating surfaces and to prevent "resin-starved" joints. Apply an even coat of the thickened mixture to one of the surfaces to be joined (Figure 4).
Thickened epoxy can be applied immediately over the wet-out surface or any time before the wet-out reaches its final cure. For most small bonding operations, add the filler to the resin/hardener mixture remaining in the batch that was used for the wet-out. Mix enough resin/hardener for both steps. Add the filler quickly after the surface is wet out and allow for a shorter working life of the mixture. Apply enough of the mixture so that a small amount will squeeze out when the surfaces are joined together with a force equivalent to a firm hand grip.
Single-step bonding is applying the thickened epoxy directly to the component without first wetting out with unthickened epoxy. We recommend that you thicken the epoxy no more than is necessary to bridge gaps in the joint (the thinner the mixture, the more it can penetrate the surface) and that you do not use this method for highly-loaded joints or for bonding end grain or other porous surfaces.
When the parts being bonded are properly positioned, attach clamps as necessary to hold the components in place. Use just enough clamping pressure to squeeze a small amount of the epoxy mixture from the joint, indicating that the epoxy is making good contact with both mating surfaces (Figure 5). Avoid squeezing all of the epoxy mixture out of the joint by using too much clamping pressure.
Any method of clamping is suitable as long as the parts to be joined are held so that movement will not occur. Methods of clamping include spring clamps, "C" clamps and adjustable bar clamps, heavy rubber bands cut from inner tubes, nylon-reinforced packaging tape, applying weights, and vacuum bagging. When placing clamps near epoxy-covered areas, use polyethylene sheeting or 879 Release Fabric under the clamps so they don't inadvertently bond to the surface. Staples, nails or drywall screws are often used where conventional clamps will not work. Any fasteners that will be left in should be of a non-corroding alloy such as bronze.
Shape or remove any excess adhesive that squeezes out of the joint as soon as the joint is secured with clamps. A wooden mixing stick with one end sanded to a chisel edge is an ideal tool for removing the excess (Figure 6).
More . . .