be used initially to immunize children in poor countries, in which high cost, heat-instability, and the necessity for injection can be significant barriers to vaccination. "We hope we can generate BCG recombinants that are tailored to particular geographical regions/' says Young, "and specifically to the major pathogens that one finds in those regions." Stu Borman
EPA seeks voluntary chemical emission cuts The E n v i r o n m e n t a l P r o t e c t i o n Agency wants U.S. industries voluntarily to make substantial reductions in their emissions of 189 toxic chemicals. Under the proposed EPA rule, companies that choose to participate in the voluntary program will be rewarded with an additional six years in which to meet stringent new clean air standards that will be taking effect over the next 10 years, if they reduce their emissions of gaseous pollutants 90% and of particulate matter 95%. Reductions will, in general, be measured against a facility's 1987 emissions. EPA Administrator William K. Reilly says the "program is structured to encourage substantial participation by industry, while at the same time ensuring [that] genuine and significant emission reductions" occur as swiftly as possible. In addition to the health and environmental advantages of early reductions, Reilly points out that industries will benefit economically by having six additional years to develop compliance strategies and choose the most cost-effective means of reducing their toxic pollutants. The voluntary program may be an especially good deal for the chemical manufacturing industry, if, as expected, it is one of the first industries to be regulated under the Clean Air Act amendments of 1990. Richard Sigman, associate director for air programs at the Chemical Manufacturers Association, explains that if a large portion of the chemical industry gets regulated in 1992—under a rule expected to be proposed by EPA
in N o v e m b e r — i n d i v i d u a l firms wanting to participate in the voluntary program will have to pledge to make the reductions before the rule comes o u t , b u t w o n ' t h a v e to achieve the reductions until Jan. 1, 1994. Companies in industries that are regulated later will have to make their actual emission reductions before an air toxics rule is proposed for their industries. In either case, if these reductions are made, the companies will have six additional years to c o m p l y w i t h t h e m a x i m u m achievable control technology standards mandated by the Clean Air Act amendments. EPA spokesman Dave Ryan points out that this compliance extension is significant. He says that "maximum achievable control technology means that you are going to have to use the very best control technology that is being used anywhere in your industry, anywhere in the U.S." EPA believes, Ryan says, that the technology will develop over the next 10 years to the point where the voluntary emission reductions won't be enough—a firm will have to go even further under final agency regulations. The chemical industry has a big stake in this issue and has been following it intently since it was just a legislative proposal. In general, Sigman says, CMA believes that EPA's proposed voluntary reduction program is "balanced and reasonable" and a "good first step" in developing air toxics regulations. He expects that a number of CMA member companies will participate in the program because "it will meet a lot of different needs and serve a lot of purposes. One, it will allow companies to make cost-effective reductions now, rather than waiting for regulations. Another [advantage] is that emissions will be reduced in a community long before that might otherwise have occurred." However, the Synthetic Organic Chemical Manufacturers Association is concerned that many of its smaller member firms won't participate in the program because of the short time limit for pledging. SOCMA also is concerned that there may not be a final rule issued by November. Janice Long
Polymer is magnetic at room temperature A v a n a d i u m - c o n t a i n i n g organic polymer exhibiting magnetism at temperatures up to 350 K has been developed by Juan M. Manriquez, Gordon T. Yee, and Arthur J. Epstein of Ohio State University, and R. Scott McLean and Joel S. Miller of Du Pont [Science, 252,1415 (1991)]. Development of the room-temperature organic magnet follows several years of work during which researchers were able to make such materials with critical temperatures only within 10 degrees of absolute zero. Ferromagnetic critical temperature, Tc, is the temperature below which a material acts as a ferromagnet. These earlier materials thus had to be cooled below liquid-nitrogen temperatures to exhibit magnetism. Now, the Du Pont-Ohio State g r o u p has created a v a n a d i u m containing polymer with a T c so high it can't be measured because it exceeds 350 K, the thermal decomposition temperature of the sample. The polymer, synthesized by reacting bis(benzene)vanadium with tetracyanoethylene, is an insoluble, amorphous black solid. Vanadium is not itself magnetic, and the polymer is contaminated by
Joel S. Miller of Du Pont demonstrates attraction of black magnetic polymer to white ferromagnet June 10, 1991 C&EN 5
News of the Week only a few parts per million of iron, much too little to account for the magnetism. The magnetism thus develops as a result of the incorporation of vanadium into the organic matrix. The polymer's magnetic field, says Miller, "is strong enough that you can actually put a magnet next to it and move it up and down the tube. It's a very noticeable effect." Potential applications for organicbased magnets include magnetic storage media (such as floppy disks) and magneto-optic materials for optical disc storage. In addition, roomtemperature organic-based magnets potentially could be used to make magnetic thin-film coatings. However, major problems remain to be solved. The material loses magnetic susceptibility over several months. And unless kept under an inert atmosphere, it reacts quickly with oxygen and decomposes. The next step is to better characterize its structure and magnetic behavior. Stu Borman
Du Pont responds to Allied-Signal lawsuit Du Pont last week filed its response to a lawsuit brought against it by Allied-Signal in U.S. District Court in Newark, N.J. Allied-Signal's suit, filed April 10, charges that Du Pont has engaged in false advertising and has illegally monopolized the $80 million U.S. market for materials used in bulletresistant vests. The two companies produce competing high-strength fiber products—Allied-Signal's Spectra, a highly oriented, high molecular weight polyethylene, and Du Pont's Kevlar, an aramid fiber (C&EN, Oct. 9,1989, page 23). According to the lawsuit, Du Pont has maintained a monopoly on the market by "unlawfully restraining Allied-Signal from introducing a new product." This has been accomplished, the suit alleges, through economic leverage, disparaging Allied-Signal's product, misrepresenting fire safety risks, and offering substantial rebates to manufacturers on condition the materials not be used together. Du Pont responds that Allied-Sig6
June 10, 1991 C&EN
nal's claims of unfair competition are without merit. And it says it will vigorously litigate the case. Both firms tout the advantages of their own fibers and disadvantages of the competing product. Du Pont charges that Allied-Signal has misrepresented the properties both of its own material and of Du Pont's. In addition, Allied-Signal alleges that after a majority of vests made with Kevlar failed to meet the National Institute of Justice's voluntary minimum performance standards in 1988, "Du Pont engaged in a concerted effort with the vest manufacturers' trade association, the Police Protective Armor Association, to discredit the NIJ standard," and supplant it "with a less demanding one that would eliminate Spectra fiber's competitive advantages over Kevlar." G. Michael Hawkins, marketing manager for Du Pont's Protective Systems, says his firm believes realistic testing standards should support the optimum combination of protection and wearability, and it has publicly voiced that conviction since the mid-1980s—long before Spectra was on the market. Du Pont does so "because of its overriding concern for officer safety and not, as Allied-Signal claims, because we want to stifle competition." Ann Thayer
Selective membranes improve gas separation Dopable, conjugated polymers show promise as a new class of gas-separation membranes. A research group at the University of California, Los Angeles, including Howard Reiss, Richard B. Kaner, Benjamin R. Mattes, and Mark A. Anderson, has used a doping technique borrowed from the synthesis of conducting polymers to control morphology. This yields very selective membranes for gas separations of industrial interest. A material of particular interest is polyaniline (C6H4NH)X, which forms very stable films in air by simple casting. This material also has simple, aqueous, acid-base doping chemistry. In general, the densest films usually exhibit the best gas-separation
characteristics. As the density decreases, film porosity increases, and all gases permeate t h r o u g h the films. In the case of polyaniline, the density of a cast film has been determined by helium pycnometry to be near the maximum of 1.257 g per cc. By a cyclic process of doping, undoping, and redoping, the permeability of the polyaniline films can be closely controlled, even tailored, within limits. This process may be repeated until the desired characteristics are achieved. The doping process effectively enhances the permeability with respect to a specified permeant. As-cast polyaniline films display the ability to separate gases, but the cycling process greatly improves the selectivity with respect to a particular mixture. For separation of a helium-nitrogen mixture, a cycled polyaniline film demonstrated a helium selectivity of 4075, compared with a corresponding value of 2200 for a poly(trifluorochloroethylene) membrane. High selectivities have also been found for hydrogen-nitrogen, oxygen-nitrogen, and carbon dioxide-methane separations, each having a peculiar cycling routine to enhance the selectivity. In each case, selectivity was considerably higher than the highest previously reported value. The doping technique was originally developed in the 1970s to enhance certain electrical properties of conducting polymers. Morphology control also affects permeability to gases. Some gases have effective molecular diameters under 2.9 A. Others may be larger than 3.5 A. Doping techniques must usually operate in such a range. Most current gas-separation membranes are asymmetric, having a thin polymer film of appropriate selectivity laid down on a structural substrate of high porosity. The usual geometry is the hollow fiber, although spiral-wound modules are also sometimes used. Gas separation with membranes has the great virtue of low-energy cost compared with thermal (cryogenic) systems. Single-pass purity has often been a problem, but this may become soluble with more selective membranes, such as doped polyaniline. Joseph Haggin
