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ContinuousWave Whaler Moderated Discussion Areas ContinuousWave: Whaler Repairs/Mods Special fiberglass material for West System
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Author | Topic: Special fiberglass material for West System |
Newtauk1 |
posted 10-22-2010 01:17 AM ET (US)
Does West System epoxy need special fiber mat and woven material? Can the same type of fiberglass cloth used for polyester resin be used with epoxy? |
dfmcintyre |
posted 10-22-2010 06:20 AM ET (US)
Yes. If it's leftovers from other projects, make sure it's clean though, i.e. no oil, grease, dirt, etc. Regards - Don |
andygere |
posted 10-24-2010 01:45 AM ET (US)
Ordinary fiberglass cloth or mat works just fine with any brand of epoxy. It will not wet out as quickly as it would with polyester resin, so be patient. A lot of extra work with the squeegee will tend to induce air and create bubbles, so take your time and let it soak in. Warming the resin a bit before catalyzing will really help with the wet out. |
Newtauk1 |
posted 10-24-2010 09:46 AM ET (US)
Thanks. The folks at West confirmed this as well. They also stated that the epoxy would chemically react with the material as it does with polyester resin. The fiberglass materials are designed to chemically react with resin to chemically bond. I was unsure if fiberglass would react the same way with epoxy as it would with polyester. If what West is stating is true then epoxy will chemically and mechanically bond to the fiberglass material. I had heard that epoxy would not have the same chemical reaction with "regular" fiberglass materials which are designed to work with polyester resin. |
jimh |
posted 10-24-2010 11:32 AM ET (US)
When WEST System epoxy resin hardens it is not from a catalyst or a catalytic reaction. WEST System resins are two distinct components, nominally called a resin and a hardener. Neither of these components will cure by themselves, and neither is a good adhesive or has much strength. The two components have to be mixed in their stoichiometric ratio, chemically react with each other, and form a new material--the cured epoxy. If there is a surplus of either reagent, that component remains in the final product. It is important to mix the components in the proper ratio because any resin or hardener in excess of the ideal ratio will not be involved in the new compound, but will remain and tend to dilute the final cured epoxy. Polyester resins are one-part resins. They are slowly curing in the can. The rate of the cure reaction is increased significantly by the addition of a catalyst. The ratio of resin to catalyst is very high, and the catalyst typically does not take part in the chemical reaction of the curing of the resin. Epoxy is a very strong adhesive. I do not believe that it chemically reacts with the material to which it adheres, that is, it does not act like a solvent and begin to dissolve the material into solution with the epoxy. I asked WEST System how epoxy makes a bond to another material. The answer is in http://continuouswave.com/whaler/radio/media/westPart1.mp3 WEST System epoxy does not contain any styrenes. My understanding is that styrene is a solvent which can dissolve other polystyrene material. |
Newtauk1 |
posted 10-25-2010 09:41 PM ET (US)
I guess the tech rep from West System had it wrong. |
Newtauk1 |
posted 10-25-2010 10:16 PM ET (US)
I did question the West tech rep about the lack of styrene in epoxy and he still claimed a chemical bond would occur coating epoxy over matte. Perhaps he ment the reaction between the West epoxy and the West resin. The project I am working on is a 1967 Squall with severe damage to the keel and delamination on about 20% of the hull. I plan to rebuild the keel with glass and Divinycell material which can be used with all commonly used resin systems (polyester, vinyl ester and epoxy). I have both polyester resin and epoxy (West). I am experimenting now with West on some of the exposed foam. I want to test the bonding ability of both epoxy and polyester resin to the foam before I proceed with the work. I paid $50.00 for the 1968 Squall hull. It has bow damage that needs to be repaired as well. I have an almost mint 1973 Squall to use as a guide and making templates from. I my end up using BOTH polyester and epoxy resin for this job. |
andygere |
posted 10-25-2010 11:52 PM ET (US)
Here's the deal: Epoxy resin will only develop a mechanical bond with cured polyester resin. This is not as strong as a chemical bond, but if you rough up the polyester/fiberglass matrix sufficiently, you can get a decent mechanical bond. Epoxy resin will develop a mechanical and chemical bond with an epoxy/glass matrix, providing the epoxy is not yet fully cured. The time this takes depends on the epoxy and the temperature, but is usually not more than 72 hours. The same goes for polyester resin, but the cure times are much faster. I recommend you read the System Three Epoxy Book (link below) to fully understand these materials. It's an easy read, and will really make your project go much better. I also recommend System Three epoxy. I've used it, West, MAS, and others, and find it to be the clearest, easiest to wet out, and most predictable. It does not blush, and has terrific shelf life (not my experience with West). I have found great prices, fast shipping and excellent service from Fiberglass Supply http://www.fiberglasssupply.com/ |
Newtauk1 |
posted 10-26-2010 12:41 AM ET (US)
Andy- Thanks for the links> John |
modenacart |
posted 10-26-2010 07:37 PM ET (US)
I think that styrene causing polyester resin to allow to bond chemically to already cured polyester resin is an old wives tail. Spectrum recommends not using it at all with their gel coats. It is also know to cause yellowing over time. |
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