Adhesives and sealants are one of those products not much thought is given, but are often critical to the successful repair job or project. I will detail some of the more useful adhesives, some that are within the RV industry, and some in other industries.
Generally, adhesives and sealants are classified as one or two part. One part adhesives cure when exposed to the atmosphere, while two part adhesives require mixing a resin and catalyst. Each type has their application, and rate of curing. Generally, the longer the adhesive requires to cure, the stronger the bond. Five minute epoxy for instance provides a moderate bond, while 24 hour epoxy will develop a much stronger bond as it has time to soak into the fibers of wood.
Some adhesives are suitable for porus materials only (wood, ceramic, etc.) while others can work on metals as well (epoxy, super glue, etc).
Some adhesives and sealants are designed for a specific application, while others are general purpose. Using the correct adhesive or sealant goes a long way in doing the right repair or perfect project.
- Dicor Lap Sealant. Intended for "rubber roofs", and generally compatable with both EPDM, TPO roof materials, this sealant is the predominant sealant used by RV manufacturers and do-it-yourself'ers. There are several styles, including leveling, and non-sag/non-leveling, depending on the application.
- 3M 5200. Although this is primarily a marine product, it is a high-performance polyurethane that can be used in certain applications for RVs. This product is actually an adhesive/sealant, with properties of both. It is waterproof, and is the sealant of choice for underwater fittings (boats). It also works particularly well with fiberglass, so any fiberglass to metal joints in a RV (trim strips, sidewalls, etc) will benefit from this product.
It is available in white and black, and in standard and quick dry formulas. A sister product is also available, 3M's 4200, which has the same sealant properties, but the adhesive is only half-strength. Using 4200 is appropriate if the pieces joined may need to be removed at a later date, while 5200 is prefered when there is no need to separate the pieces. Neither 5200 or 4200 should be used on rubber roofs.
- Proflex RV Sealant. This is also an adhesive-sealant, and not appropriate for rubber roofs. It is more flexible than silicone, so it is a good choice where items to be sealed are under stress or vibration (window seals, etc). It will displace water so it is a good choice for emergency repairs (water leaks, etc).
- 3M Marine Grade Silicone. This is a high performance quality silicone sealant, which does not have the properties of 5200 or 4200. It is vastly superior to the typical silicone "bathtub caulk" which is commonly found in home centers. Silicone is appropriate when there is no requirement for a mechanical bond, but rather just a seal. Silicone can often be removed at a later date, which makes it useful for items that may require removal at a later date.
- West System Epoxy: Also popular in the boating world, this is some of the best epoxy you can buy. The catalyst (hardner) is available in a quick (24 hours) or slow (2~3 days), so it is appropriate when you can immobilize the pieces to be joined for several days.
The hardner is typically purchased separately from the resin, and you can also buy powders that can be added to the epoxy for special purposes - such as fairing compound (easier to sand), gap filling (for joining two items that are not completely flush), and other purposes.
A pump dispenser system is available for this epoxy, and I highly recommend using it as the resin and hardner do not mix 50/50. Using the pump system allows more accurate metering of the product. Epoxy is waterproof, but it is fairly susceptable to UV damage, so painting or varnishing over the glue joint is recommended.
- Gorilla Glue Epoxy: More suitable when you need a quick epoxy solution, but it is not as strong as the slower cure epoxy due to its fast cure time, which does not allow the epoxy to penetrate the pores of the material being bonded.
- Cyanoacrylate (Super Glue): This is an extremely quick drying glue, and will join almost anything together. It is not appropriate for clear plastics (lexan, acrylic, etc), as the glue fumes as it cures. The fuming can damage clear plastics. It is available in both a gel (for gap filling) and standard viscosity versions. Generally, you will want a very thin coat of glue on your glue joint as applying a thick coat will cause the glue to run, and potentially leak into areas that you do not want glued (such as switch bodies, etc).
An optional companion product - CA Accellerator is an instant curing agent that will form a shell on the outer surface of the glue - holding it in place (as well as the joined parts). Super glue is perhaps the most difficult glue to successfully use.
- Gorilla Glue (the original): This is actually a two part glue, as it cures with moisture. You can accellerate the curing time by wetting one of the items to be glued, or spraying water on two parts after they are joined. Clamping the glue joint is highly recommended. Gorilla Glue expands as it cures, so it is good at gap filling.
- Seal-A-Tube: This interesting product inserts into the end of an open 12 oz cartridge (the kind that you use with a caulking gun). The purpose is to seal the open end for an extended service life. Most RV owners will not use the entire amount of product in such cartridges and the product would otherwise dry out before use.
- Little Red Cap: Having a similar purpose as the Seal-A-Tube, these caps are more or less a rubber boot for the open end of glue cartridges or bottles. Again, extending the open shelf life of the product is the goal.
- Glue Syringes: These are indespensible, but often they are intended for wood glue, which has a higher viscosity than some of the other adhesives. Ideally, you would have a range of glue syringes that cover all of your adhesives and sealants. Alternatively, look for glue syringes that have tapered tips, so you can cut the tip to the diameter needed.
- Clamps: Some projects must be clamped while the glue dries. Clamping generally improves the bonding of the glue joint.
- Glue Additives: Additives can typically be added to epoxy and sometimes to other types of glue. Additives are powders that change the properties of the adhesive, which includes gap filling (406 Colloidal Silica) as well as fairing (410 Microlite Filler) allowing the glue material to be sanded/blended in (faired). Typically these additives change the viscosity to a peanut butter consistancy.
- Gloves and Towels: It should go without saying that you will at some point make a mess of yourself, so you will at least want some disposable gloves and perhaps paper towels.
- Safety Gear: In addition to gloves, you may find some glues and additives may present an eye, lung, or skin irritant, so you may wish to use safety glasses, eye shield, or a resperator.
- Stir Sticks and Cups: Often you will need to mix 2-part adhesives, such as epoxy. This is best done if you have stirring sticks (popcycle sticks) and cups. The sticks are usually available in the craft section of your local department store. Paper cups, such as Dixie Cups work well, and paper cups are prefered over plastic cups as the plastic may melt during the mixing, either due to the chemical or heating characteristics of the glue (some epoxies can get quite hot during the mixing stage).
- Surface prep and Cleanup: No project is completed until it is cleaned up, both over-spill and what you get on yourself. As well, the best glue joints occur when the surface is properly prepaired. Most glues and adhesives have a specific recommendation for what is best for surface prep and clean up, and Isopropyl Alcohol will work on most glues.
Other glues and sealents may have a specific thinner of cleaning solvent that is also available. One caution though is that some sealants and glues may not cure if exposed to alcohol, so you will have to ensure you completely remove the alcohol (surface prep). Make sure you don't use "Rubing Alcohol" as it typically has Lanolin (a wax) or other additives in it that can leave a residue.
This is probably more than you ever wanted to know about adhesives and sealants, and this short article cannot begin to illustrate how to properly use each one. Rather, these are common products that all have application in RV repairs and projects. If you find you need to use a particular adhesive or sealant, read the manufacturer's recommendations for proper use of the product.
Generally all of the adhesives and sealants shown here are fairly safe for use by the RV owner when following the manufacturer's instructions. Still, some items such as the powder additives can be an eye and lung irritant, and some glues fume as they cure, which could also cause eye, lung, and skin irritation. Read all instructions and safety material concerning each product prior to use. Some adhesives and sealants, such as two part Polyurethane do present some danger, and are not appropriate for use by the RV owner.
Ensure you read all safety and environmental instructions for the adhesive or sealant you intend to use to ensure your personal safety and health of the environment.
Use appropriate safety gear, including gloves, resperators and the like as needed when handling these products.