David, Why do you want to change? Silicones are generally more expensive materials and typically require a greater thickness/mass to achieve the same protection performance as an Acrylic. As a general rule of thumb, if you were to look at the molecular level you would find that an Acrylic or Urethane will have molecules the size of a tennis ball. Silicones and Epoxies would be the size of basketballs. Considering that all coating breathe and permit air, which may contain water vapour, to migrate in and out of the film - then it follows that you should require more coating with the silicone so you have a double disadvantage. Furthermore, silicones generally swell in the presence of hydrocarbon solvents. So your thought of poor performance in the presence of fuel oil would probably be correct. However, how much fuel oil? Vapour, mist or spray? Maybe a urethane would be better. If it is the environment that concerns you (rightly so!) then consider coatings made up from the new LOC (VOC exempt) type solvents. If you are proposing to use the same spray line for acrylics and silicones, you will almost certainly create problems, specifically de-wetting. You really need to look at dedicated feed lines for each and keep them that way! Regards, Graham Naisbitt __________________________________________________________________________ [log in to unmask] Concoat Ltd Alasan House, Albany Park Camberley GU15 2PL UK http://www.concoat.co.uk -----Original Message----- From: David Paluck <[log in to unmask]> To: [log in to unmask] <[log in to unmask]> Date: 11 June 1998 17:28 Subject: [TN] silicone conformal coatings >Hello. We are considering a change in conformal coatings used on our >PCB's. Currently in use are a silicone elastoplastic resin flow coating >and an acrylic spray coating. We would like to switch to an automated >coating process using a low-VOC silicone elastoplastic resin and eliminate >the use of acrylics. However, we expect to meet some resistance from our >customers, especially those in the paint industry, who think a silicone >coating will not perform as well in resisting paint and/or fuel oils. >Also, is there a possibility of silicone causing flaws in paint? (e.g. >coating with silicone resin a circuit board used in a paint sprayer.) Any >feedback would be appreciated. > >Erin Macy >Electronic Systems, Inc. > >################################################################ >TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c >################################################################ >To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: >To subscribe: SUBSCRIBE TechNet <your full name> >To unsubscribe: SIGNOFF TechNet >################################################################ >Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. >For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 >################################################################ > > ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################