Re: [VFB] RE: Thinning Flexament

[Henk Verhaar]

On 15 Nov, 2006, at 4:26, Ian Mitchell wrote: Nev, I am not sure what the solvent in fllexament is. See previous post. But I can think of 2 causes for your problem: 1. YOur acetone is not pure acetone - commercially sold nail polish remover these days is not 100% acetone. No acetone is pure. It is hygroscopic. At the very least it will contain/accrue some water. This would especially be true for old stock, such as your lifetime supply of acetone mentioned below. Unless more than 20%, most impurities in acetone will not significantly change its solvent power. 2. The solvent in flexament is not acetone, Correct. and the acetone has reacted with the solvents/components of flexament. SOlvents usually do not react with other solvents or solutes. Tradional solvents were selected in part for their solvation powers, in part for their (relative) inertness. What happened in this particular case is an example of solvent/solute incompatibility. It is comparable to what happens when you add acetone to an aqueous solution of table salt. Water and acetone are miscible. Table salt is soluble in water but next to insoluble in acetone. For a given strength of salt solution in water, there is a minimum amount of acetone that you can add to the water so that the salt will no longer dissolve in the acetone-water mixture. At that point you will see clouding from the salt precipitating out of the solution. Slowly adding acetone up to this point will have the salts precipitate differently than when you add the required amount of acetone all at once. With the flexament, the silicone rubber polymer is soluble in toluene and PCE but not in acetone. As you add acetone, the rubber precipitates as a solid mass. Cheers Ian PS I have a pint of pure acetone that the Chemist kindly sold me ( a lifetimnes supply) which I use to thin my favourite head cement (clear nail varnish). The acetone it cost a few bucks but it was about a tenth of the cost of the same volume of commercial nail varnish remover.  The Chemist actually warned me to avoid spilling acetone on pretty much everything as he said it would dissolve most modern materials (plastic/lino/paint...etc...) Mmm, some things are very sensitive to acetone, such as lacquers and some natural resins. Some plastics are also ruined by acetone, notably ABS (DON'T spill acetone on you ABS woodwinds (recorders, clarinets, hoboes, pretty much all high-end 'plastic' woodwinds are made from ABS), and please don't ask how I know...). Polystyrene e.g. is easily dissolved in toluene and xylene. Most plastics however are fairly resistant to acetone. At high exposures (think daily exposure for a working life) acetone is a liver toxin. Nothing to worry about with incidental exposure though. Henk =============================== ><(((((º> =============================== | Dr. Henk J.M. Verhaar             | e-mail: [EMAIL PROTECTED] | | Ecotoxicoloog en vliegbinder      | tel:    035 656 2128              |  | Stichts End 17                    | mobiel: 06 26 136034              | | NL-1244 PK Ankeveen               | web:    www.xs4all.nl/~flyrod     | =============================== <º)))))>< ===============================