Werner Tg is not a fixed value, even for a single given sheet of laminate. It can drop by 30°C or possibly more depending on the history of the resin, for example, if it has been subjected to a humid atmosphere or to the vapours of certain chemicals. If you extend it to multiple sheets, those sheets nearest the platens in the laminating press will have a different Tg to those in the centre of the pile, because the temp profile is not the same. Then, when it's a matter of different batches of resin mix..., treater drying cycle..., prepreg age before pressing... etc., the tolerance becomes very significant, even at the laminator's goods-out door. By the time it reaches the assembler, a ± 25-30°C tolerance could be normal. This does not take into account the tolerance of measurement of a physical phenomenon which is gradual in its application (the Tg depends on the polymer MW, which is quite variable); there is no sharply defined transition from a conchoidal fracture to a fluage. Brian Werner Engelmaier wrote: > Hi Doug, > Of course I do not suggest Tg 178 instead of 175; but the slash sheets give > ranges on the same sheet thast include Tg's with 50 degree differences--they > should perhaps be no ore than about 20. > > > > Werner > > --------------------------------------------------- > Technet Mail List provided as a service by IPC using LISTSERV 1.8e > To unsubscribe, send a message to [log in to unmask] with following text in > the BODY (NOT the subject field): SIGNOFF Technet > To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) > To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest > Search the archives of previous posts at: http://listserv.ipc.org/archives > Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 > ----------------------------------------------------- > -- http://www.cypenv.org Cyprus environment/energy http://www.cypenv.org/worldenv World environment/energy http://www.cypenv.org/weather Cyprus weather http://www.cypenv.org/smf/index.php Environment/energy forums http://groups.yahoo.com/group/cypnature/ Cyprus nature forum --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------