News of the Week ministration that the terms of retir ing board members would not be renewed. Yosie says the policy was a mis take and that he recommended against it. In fact, he adds, he in tends to recommend that the num ber of board members be raised from the current 37 to as many as 60. "My intention is to reappoint sever al of those whose terms ran out," he says. D
New polyacetals may boost Du Pont's sales Du Pont has high hopes that two toughened grades of polyacetal res in it introduced last week at a Soci ety of Automotive Engineers meet ing in Detroit will extend uses for this engineering thermoplastic. Says Du Pont polymer products vice president Nicholas Pappas: "We expect this discovery to be a major factor in increasing sales of our acetal resins 50% within four years and doubling sales before the end of the decade. Additional advances stemming from this discovery could result in even more dramatic growth into the 1990s." In other words, an nual sales growth may push up to 10% from the traditional 8%-per-year increases of the past.
Du Pont's Flexman measures a test bar of Delrin ST super-tough acetal resin β
March 7, 1983 C&EN
One other implication of the new products is that Du Pont may add hefty new capacity in the next few years. The company does not reveal its present capacity, but it's estimat ed that Du Pont can make 75 mil lion lb per year of polyacetal at its Parkersburg, W.Va., plant. The oth er producer, Celanese Plastics & Spe cialties Co., has a 125 million lbper-year plant at Bishop, Tex., which produces a copolymer of formalde hyde and ethylene oxide. What has Pappas so excited is that research associate Edmund A. Flexman Jr., working at Du Pont's Wil mington, Del., laboratories, cracked the secret of how to alloy polyacetal with an unnamed elastomer. In ad dition to increasing the resin's in herent lubricity for abrasion resis tance, elastomer alloying also en hances impact, flexural, and tensile fracture resistance.
In the auto industry, these prop erties suggest uses in parts for seat belts, steering columns, windshield wipers, gears, gas caps, exterior trim fasteners, push/pull controls, and locks. Uses in other industries might include crash helmets, conveyors, parts for small engines, and impact gears, cams, and slides. The thermoplastic alloys can be injection molded or extruded with barrel temperatures profiled from 380 to 430 °F. Du Pont· will supply resin in moisture-proof bags ready for use without predrying. The tough grade will sell for $1.60 per lb and a "super tough" grade for $1.72 per lb. As one measure of toughness, the tough grade has im pact strength of 2.1 lb per inch in the Izod test; this is 50% greater than that of unmodified polyacetal. The impact strength of the supertough grade is 17 lb per inch. D
Fluorinated plant steroids kill insect pests Highly specific insecticides that are nontoxic to other organisms may result from research on 29-fluorophytosterols carried out by organic chemistry professor Glenn D. Prestwich of the State University of New York, Stony Brook. Most planteating insects have dealkylating en zymes that convert such plant ste roids to toxic fluoroacetate; other organisms, from bacteria to mam mals, including insects that eat oth er insects, do not. Fluoroacetate in hibits the citric acid metabolic cycle in insects by converting to (-)-erythro-2-fluorocitrate, which inactivates either aconitate hydratase, an en zyme in the cycle, or a citratetransporting protein. The research was reported in the premiere issue of Bio/Technology, a monthly magazine of news and original research papers in industri al biology, from the publishers of Nature. Working with postdoctoral stu dents Apurba K. Gayen and Toni B. Kline, and with graduate student Seloka Phirwa, Prestwich synthe sized the 29-fluoro derivatives of sitosterol, stigmasterol, clionosterol, poriferasterol, and fucosterol. The Stony Brook workers tested the ef fects of these compounds on mortali
ty and inhibition of weight gain and maturation in the pupae of to bacco hornworm larvae. The most potent was 29-fluorostigmasterol, which killed 50% of larvae at a con centration of only 4 ppm in the wheat germ diet on which larvae fed. Prestwich suggests that electrondonating effects of the additional, strategically placed, carbon-carbon double bond in 29-fluorostigmaste rol counteracts electron-withdrawal by the nearby fluoromethyl group. This balancing of electronic effects may speed up production of 29fluorostigmastatrienol and its epox ide as intermediates on the route to splitting off fluoroacetate. The SUNY group selected C-29 as the fluorination site because it is remote from functional groups in other parts of the molecules and thus should not cause disruptions in overall steroid metabolism. In earlier work, they found that 24-, 25-, and 26-fluorophytosterols were nontoxic to insects, as were 20-, 22-, 24-, and 25-fluorocholesterol. The research was supported by the National Institutes of Health, National Science Foundation, Alfred P. Sloane Foundation, and Camille and Henry Drey fuss Foundation. G
