CHEMICALS
Close Look at N e w Plastics Uses for PVC Pearls, polyoxymethylene a n d poly carbonate resins shown at SPE meeting
nents. In tests it retains 90% of its original dielectric strength after seven days exposure at 275° C. The varnish contains 6 5 % silicone solids in xylene, yet has low viscosity, thus better pene tration and wettability, according to the company. C 1 ί Sodium-copper cyanide d o u b l e salt
carried out first at Du Pont and now for use in copper plating solutions made dustry probed into the field of rein with potential users and processors with sodium cyanide is n o w a regular forced materials (see page 6 0 ) , engi points to these general applications: product of D u Pont's electrochemicals neers took a look at "pearls" made of department. T h e company says that • Mechanical—gears, racks, and bear use of the double salt eliminates the poly (vinyl chloride) and new uses for two new plastics—Delrin and Lexan. ings. several steps required to dissolve cop • Plumbing and hardware—valves, per cyanide properly. These highlighted the new materials C2 list at the 14th Annual National Tech handles, and others. • Rust preventive coating in a water nical Conference of the Society of Plas • Appliances—hinges and the like. tics Engineers. • Automotive—special gears, valves, emulsion is available from Dearborn Chemical. It can be applied b y dip, The pearls, made by a new polymer wedges, caps, and knobs. brush, or spray and dries to a soft waxy ization process, may find a place in • Consumer—tableware, tumblers, protective film. C3 electrical applications. Delrin seems many others. suitable for a wide range of uses (even • Packaging—aerosol bottles is one • Tetrafluoromethane is now offered aerosol bottles), while Lexan has stirred example. for research purposes b y Matheson. up some interest as a material for lenses. The gas comes in three cylinder sizes PVC Pearl polymer, say Escambia's All of Delrin made now (on a small Robert Si Holdsworth, W . Mayo Smith, semi-works scale), says Cogdell, is used at pressures of about 500 p.s.i.g. The and John T . Barr, is a suspension-proc exclusively in Du Pont's highly selective minimum purity of the gas is 95%, the C4 ess product. But it differs from resin testing program. Aim here is to get company says. made by conventional suspension or more data on product properties, proc^Simulated iodine-131 standards, emulsien processes i n that it has a larger essability, and end-uses. now available from N e w England Nu particle size and is dust free, HoldsTwo types of the polyoxymethylene clear Corp., have a half-life of about worth claims. Almost 80% of Escam resin are in testing—a general purpose bia's product is retained on an 80 mesh molding one, and one for general pur 10 years. To make the standards, the company combines barium-133 and screen, the rest on a 40 mesh screen. pose extrusion. cesium-137 in proper proportion widi Three grades of Pearl resins are now • Pilot Plant Resin. General Elecmade commercially, says Holdsworth. tric's Lexan polycarbonate resin wasn't special absorbers to yield a gamma ray These grades differ in molecular out of the lab when first announced spectrum similar to that of iodine-131, weight. And all of them, he notes, can (C&EN, April 8,1957, page 20). Now, the company says. They are used to C5 be processed in standard extruders, though, it's made in a pilot plant. And calibrate iodine-131 doses. mills, internal mixers, calenders, and the pilot plant is readily expandable, t Crete-Prep, made b y Concrete other equipment used by the plastics says W. F. Christopher. I n fact, plas Chemical Products, is a nonalkaline tics engineers can now consider the industry. cleaner for concrete, brick, stucco, Escambia is entering PVC Pearl in resin for design work. stone, cement block, ceramic tile, and the wire insulation market. This use Christopher says that Lexan's proper vitreous china. It gives off no harmful takes up a big slice of all poly (vinyl ties suggest a lot of uses. One use fumes and will not irritate eyes, nose, or chloride) production, since vinyl insu that's causing "considerable interest," skin, the company says. C6 lation has good electrical insulation he claims, is making optical parts—out properties, wide color range, is easy to door lenses, instrument lenses, and • Peroxidol 7 8 0 , a light-colored, poly make, and costs relatively little. The lighting devices. Resin properties that meric, epoxy-type plasticizer, is the first Pearl product, according to Holds- point to this application are heat re of a new series of products for the worth, was tested by a large insulated sistance, dimensional stability, and im vinyl field being introduced by Reichwire maker. Results, h e claims, are as pact resistance. hold Chemicals. It has a high resist GE is now running a comprehensive ance to temperature and weather, the good or better than those obtained "with development and expansion program on company says. other commercial PVC resins. C7 > Delrin End Uses. D u Pont's Del the resin, says Christopher. rin acetal resin (C&EN, Dec. 3, 1956, • N e w organic flocculating agent page 5926)—a high melting, highly comes from Union Carbide Chemicals. crystalline formaldehyde polymer—may It's a high-molecular weight grade of g o commercial by mid-1959. But al ί Silicone insulating varnish, R-610 Polyox water-soluble resin. Material is ready, according t o J. F. Cogdell and Silicone, is being made by Union Car available in development quantities as R. H. Hardesty, end uses can be pre bide for use in coating and bonding white, crystalline granules, according to dicted. A n extensive end-use search Class Η electrical insulation compo Carbide. C8 V v HILE t h e Society of the Plastics In
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C&EN
FEB. 17, 1 9 5 8
