ing the glass with carbon fibers yields a material with a flexural strength of 60,000 p.s.i. and a tensile strength of 40,000 p.s.i., Mr. Kossoff points out. The main deterrent to growing use of carbon fibers has been the high cost of the fibers, which have been priced at $50 or more per pound. But increased consumption (200,000 pounds in the U.S. last year) is spawning price reductions, and Mr. Kossoff foresees the price halved by 1978, perhaps dropping to between $5.00 and $10 per pound within 10 years. When this happens, the replacement of die-cast metal parts with carbon fiber-reinforced thermoplastics will accelerate. By 1979 annual output in the U.S. might exceed 1 million pounds and could approach 3 million to 6 million pounds by 1984, depending on price. This amount is in sharp contrast to the 50,000 pounds produced in the U.S. last year. LNP in Malvern, Pa., is the main domestic producer. Elsewhere, Japan's Toray Industries and the U.K.'s Courtaulds are active in the business. Thermoplastic elastomers is another group of materials for which Mr. Kossoff predicts a bright future. "By 1984 total thermoplastic elastomer sales in the U.S. could total nearly a billion pounds, compared to less than 150 million pounds in 1973," he says. Here again, growth will come about by modification of existing technology. Thermoplastic elastomers based on polyurethanes, styrene-butadiene-styrene block copolymers, polyesters, and polyolefins are already established. During the past five years, eight U.S. producers have entered the field to raise the number to 12.
Kossoff: modify existing materials The reason for the upsurge in interest is that unlike thermoset elastomers such as neoprene and ethylene-propylene-diene monomer, which must be cured by a fairly costly processing step, the newer thermoplastic elastomers with matching properties can in many applications be injection molded. They are being used for making such items as automobile bumper parts, tubing, and belting. Among the chief obstacles to wider acceptance is their low operating temperature and mediocre mechanical properties. Mr. Kossoff believes that introduction of novel* diols into polyester elastomer formulations, for example, and development of new block copolymers, will overcome some of the disadvantages and lead to ther-
Smog chamber study hunts research discrepancies A specially designed glass smog chamber containing rows of suspended polished aluminum plates creates multiple reflections of Dr. Raphael J. Jaffe, holding a test instrument at the end of the chamber. Dr. Jaffe is project director for a Lockheed Missiles & Space Co. smog chamber study. In the study, smog-forming chemicals are pumped inside the chamber to react with the aluminum under artificial sunlight, the aluminum plates being similar to those used to enclose some laboratory smog chambers. Aim of the Lockheed study is to determine why differing results have been obtained in past smog chamber research.
30 C&ENJune24, 1974
moplastic elastomers with superior thermal, mechanical, and weathering properties. New diol and dibasic acid combinations also might lead to thermoplastic polyesters with improved thermal resistance, opening the way to their use in under-the-hood auto parts and in heat-resistant hosing. Mr. Kossoff mentions polymers made from 1,3-propanediol and terephthalic acid or from 1,4-butanediol and 2,6-naphthalene dicarboxylic acid. Such materials could constitute second-generation polybutylene terephthalate-based engineering thermoplastics, which first appeared commercially in 1971 and have grown since to a consumption level in the U.S. exceeding 10 million pounds last year. Use might climb to 70 or 80 million pounds by 1980. However, 1,4butanedioFs tight supply and fairly high cost (currently about 36 cents per pound) could hinder the growth pattern. At the same time, these factors could stimulate the search for alternate diols. In the fabrication field, Mr. Kossoff forecasts that "high-modulus organic fibers will become major commercial products, initially for tire belting as steel cord replacement, the reinforcement of plastics and rubbers, and as a substitute for industrial wire cable." Du Pont seemingly shares this view. The company has unveiled plans for a 50,000 pound-per-year plant to make its Kevlar high-modulus fiber, the first commercial unit of its kind anywhere. Several materials are candidates for such fibers, with aromatic polyamides looking the most promising. Increasing vandalism has prompted replacement of glass windows with acrylic or polycarbonate sheet in many areas. However, these materials tend to scratch easily and have poor chemical resistance. These drawbacks largely can be overcome by treating the sheet with such proprietary coatings as polysilicic fluoropolymers to improve abrasion and solvent resistance. "Sales of the modified sheeting likely will exceed $10 million this year and could top $50 million by 1984," Mr. Kossoff remarks. Probably the most exciting development in the plastics fabrication arena centers on reaction injection molding. General Motors and other U.S. auto makers are looking into this technique as a likely means for making large structural body parts directly from a urethane solution. The process involves in situ polymerization of a highly catalyzed liquid urethane and could be cheaper than molding the large sections from thermoplastic elastomer pellets. Besides, Mr. Kossoff observes, there is a lack of injection molding equipment of a size suitable for making sections as large as those being contemplated. By the 1980's, the amount of monomers used for this outlet alone could reach several hundred thousand pounds annually, he predicts.
