The dust is beginning to clear after the initial confusion caused by the State of California making the use of MDA illegal, at least, in the industrial environment. Since Scaled Composites does not subject its employees to MDA or styrene (contained in Safety-Poxy) RAF reasoned that homebuilders should have the same benefits. A lot of frantic testing was conducted and, as a result, PTM&W (PR2770/PH366C) was recommended. Many builders complained about the workability of this rather thick (viscous) epoxy system so the tests and evaluations continued. Today, we have an improved, thinner PTM&W (PR2032/PH3660) which has even better physical properties than the original PTM&W and we have Hexcel's 2427 system which has the advantage of using the Safety-Poxy ratio pump "as is"., that is to say, the mix ratio is 44:100. The workability and "wet out" qualities of Hexcel 2427 are excellent and the physical properties are adequate.
Caution: Both of the above epoxy systems have higher exotherm problems than Safety-Poxy. The only place this can cause a problem is when you join foam blocks. This is very important. You cannot have a micro joint between two foam blocks any thicker than 1/8". You must be absolutely certain that your micro joint, or the space between the foam blocks, is kU that 1/8" (1/16" is best). Any more than 1/8" will cause an exothermic reaction, due to the high insulating properties of the foam, and serious damage to the foam and loss of structural integrity of the foam joint will result. This is not as good as Safety-Poxy (which allowed a safe foam block joint up to 1/4" thick), but both of these epoxy systems are completely free of MDA (a known carcinogen) and styrene (highly allergenic). Soooo..... you have your choice.
Please let us have your observations as feedback for the CP. We. and all of our readers, are interested to hear about personal experiences, good and bad!