I/EC
Forecast
P O I N T I N G THE E D I T O R I A L
FINGER
AT T O M O R R O W ' S
PROGRESS
Light-Sensitive Plastics
Lead Cement
Photography is facing the greatest revolution since the daguerreotype. This is the promise of photosensitive plastics. First practical use— a grainless, silver-free, plastic base copying film—reached the commercial market less than a year ago. Projection slides and negatives are m a d e simply by placing the film against the negative, exposing it to fluorescent light for a minute, then dropping the exposed film into boiling water. Although not in the commercial stage yet, Du Pont's Dycril, a light-sensitive plastic, looks like a good bet to revolutionize photocopying and printing. A photograph of the subject is made, the negative is exposed to Dycril plates under ultraviolet light, and the unexposed portions are removed by washing in an alkaline solution. W h a t remains is a complete printing plate. Once the plate has been made, it can be finished and mounted on a press in about 20 minutes. Necessary equipment to prepare the plates—possibly as little as $5000: cost of photopolymer plate—about $10 a square foot.
A new class of metalic materials has been demonstrated in research at Battelle Memorial Institute. These materials are "lead-cemented" alloys made by mixing molten lead with finely divided particles of other metals or materials. The result is a compound having the properties of both lead and the second component. Pos- sible application—radiation shielding, corrosionresistant process equipment, gasketing materials for temperatures which would burn up plastics, bearings for automobiles, and rotating shafts.
N e w Polymers — New Problems In the effort to synthesize polymers having high rigidity at elevated temperatures, polymer chemists are experimenting with new combinations of atoms, including some of the metals—aluminum, magnesium, and tin. O n e such polymer has a backbone chain of alternating atoms of aluminum and oxygen, and side chains of oxygen, silicon, and hydrocarbon groups. Cast from solution in xylene, it melts at about 850 ° F . Another possible polymer is polyphenyl, a string of benzene rings strung out end to end. Theoretically this should have good properties, but no one has found a way to make it. It is too insoluble to use known techniques. Yet another is a polymer ring formed from polyacrylonitrile. Although it is high in heat resistance, it is not a commercial product because of the very high rigidity of the molecular chain. These are but a few of the problems in the polymer field, but m a n y of them are well on the way to being solved—narrowing the gap between properties of polymers and those of metals and ceramics. T h e symposium on inorganic polymers at the ACS Atlantic City meeting will provide timely information in this area.
Fly Ash-An Asset? W h a t is now considered to be a nuisance may yet prove to be a valuable plant by-product. Fly ash is produced at steam plants when coal is burned to generate electricity. T V A has started to sell fly ash to a newly formed company. T h e ash is used by producers of cement products to improve quality and save on the amount of cement used. Large quantities of this modified cement have been used with marked success in construction of new navigation locks at Wilson D a m and two powerhouses with substantial cost savings. Another possibility—cement for highway construction. Fly ash is part of the lignite slag aggregate being tested for bituminous road surfacing in Texas.
Castor Oil Going into Plastics Although most of the 120 million pounds of castor oil used in this country each year is imported, interest in domestic production has grown. A market has already been established for castor oil as a raw material in jet-engine and industrial lubricants, in cosmetics, and medicines. Latest field to come under study is plastic foams. Polyurethane foams made with castor oil may range in texture from soft and spongy to hard and rigid. Variations can be produced by changes in the amount of oil and other ingredients used and by changes in processing techniques. High oil content foams, 70 to 8 0 % castor oil, have textures much like that of soft foam rubber. Estimates are for a possible 20 million pound per year market for castor oil in plastics. V O L . 5 1 , NO. 9
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SEPTEMBER 1959
29 A
