Fabry-Perot velocity


PGT Molding Resins The latest prominent thermoplastic polyester, p oly (cycl oh exyl dim ethyl en e terephthalate) (PCT), was first produced by Eastman Kodak in the 1950s as a polyester fiber (5). PCT was introduced as a mol ding resin in 1987 in glass-filled and flame-retarded grades with specific end uses (7). Eastman is the sole polymer suppHer from the plant in Kingsport, Teimessee, although some polymer is beheved to have been suppHed to General Electric, who marketed it as part of their Valox range of thermoplastic polyesters. The targeted end uses appear to be connectors for both the electronic and automotive markets. A development in the electronic market associated with miniaturization is the so-called surface mount technology (SMT) (145). This has already taken over about 50% of the electronic connector market and the trend is expected to continue. There is a much lower level of penetration of this technique in the automotive connector market but its use is also expected to grow. The SMT process uses a solvent vapor-heated reflow soldering process in which the whole electronic component is immersed in hot vapor to melt the solder alloy and allow it to flow. The vapor temperature is usually about 215°C (420°E) for 60/40 tin—lead solder. This puts greater thermal demands on the thermoplastic parts and as a result the blistering temperature of these components has to be above the soldering bath temperature. This is beyond the capabiUty of PBT and most nylons, except nylon-4,6. Interestingly, the heat-deflection temperature (HDT) is not a very precise guide to performance in the blistering test, although obviously the higher the HDT, the better. PCT has a HDT around 260°C (500°E) and its blistering performance under vapor reflow soldering conditions is very good. PCT is significantly less expensive than the ultrahigh performance Hquid crystalline polymer (LCP) engineering resins. One specific advantage of PCT is that it has similar flow characteristics (although at higher temperatures) during mol ding to both PET and PBT which means that extensive mold redesign is not necessary which makes it attractive to molders.  [c.299]


High pressure shock compression of solids (1992) -- [ c.0 ]