At 12:12 AM 6/3/2006, you wrote: > I read tons of archived messages but I couldn't one that answers > my question. If it has been asked before, I apologize. > The amount of hardener mixed in with the resin affects the pot > life of the epoxy. All factors remain constant, more hardener > gives you less pot life, right? > Q1. Does the amount of hardener affect the strength of the epoxy mixture? > Q2. Does the amount of hardener affect the curing time of the > epoxy mixture? > Q3. What happens if you mix with wrong ratio of resin and > hardener called for by the manufacturer? > > Thanks for you help.
Your assumption about pot life is incorrect. Epoxy should be mixed as close to exactly as specified. If the ratio is off by more than about 5 percent, the physical properties of the cured epoxy will be sub-standard. Pot life is dependent upon the ambient temperature, the quantity of epoxy being mixed, or the hardener being used. The chemical reaction will progress faster at higher temperatures. The chemical reaction is exothermic and will make its own heat which can affect the cure time. Some brands use different hardeners to get different pot life or allowable working temperature ranges. If you want a quality product, you mix the epoxy exactly as the manufacturer specifies. Anything else will reduce the strength or alter the properties in an bad way. The two different components in epoxy combine chemically and the ratio must be very close or there is an un-reacted portion left over. The chemical reaction is different for polyester based products. The catalyst (methyl ethyl ketone) causes the resin to form a series of long chemical chains. More catalyst makes the reaction happen faster. Don Reid - donreid "at" peoplepc.com Bumpass, Va Visit my web sites at: AeroFoil, a 2-D Airfoil Design And Analysis Computer Program: http://aerofoilengineering.com KR2XL construction: http://aerofoilengineering.com/KR/KR2XL.htm Aviation Surplus: http://aerofoilengineering.com/PartsListing/Airparts.htm EAA Chapter 231: http://eaa231.org Ultralights: http://usua250.org VA EAA Regional Fly-in: http://vaeaa.org
