Improved polycarbonate weds toughness, rigidity Last Friday, General Electric took the wraps off its new Lexan 500 polycarbonate, latest entry in the 1970 composites sweepstakes (C&EN, April 6, page 14). Describing Lexan 500 as having "the most metal-like combination of toughness and rigidity of any plastic material ever made," GE expects its improved polycarbonate to replace metals in many applications previously resistant to takeover by engineering thermoplastics. Until now, GE says, few plastics have been able to combine high impact strength with structural rigidity: The more rigid materials, such as glassfiber-reinforced thermoplastics and some of the phenolics, have tended to be brittle; unfilled thermoplastics with high impact resistance, such as nylon and standard Lexan, have been lacking in rigidity. But, asserts John Zaremba, GE's senior market development specialist for Lexan resins, "A stress-strain diagram for Lexan 500 looks like one for low-carbon steel/' The new composite does contain a small amount of glass fiber, Mr. Zaremba reveals; nevertheless, it boasts an izod impact strength (notched bar) of 4 to 6 foot-pounds per inch, and ductile impact strength (falling 1-inch dart) of more than 125 foot-pounds per inch. At the same time, it has a flexural modulus (measure of rigidity) of 500,000 p.s.i.-nearly 60% better than standard Lexan's, GE points out—and a high degree of creep resistance. The resin is self-extinguishing, UL-approved for sole support of current-carrying parts, and provisionally UL-rated for continuous use at 221° F. Heat deflection temperature is 288° F. at 264 p.s.i.
Dimensionally stable.
Molding
temperature is about 550° F., about the same as for other polycarbonates. But shrinkage in the mold is only 2 to 3 mils per inch, compared to 5 to 7 mils for standard Lexan. GE notes that this dimensional stability makes Lexan 500 particularly suitable for parts requiring close tolerances. Easier processing, including the elimination of secondary finishing operations, will make Lexan 500 less expensive, on the basis of finished part costs, than aluminum or zinc, GE maintains. Additionally, the Lexan 500 part will offer the advantages of corrosion resistance, electrical insulation, and lighter weight. Prices for Lexan 500 start at 85 cents per pound for truckload quantities of either translucent natural (offwhite) or opaque black resin. Custom colors are available at higher prices, as are smaller quantities.
SCIENCE/TECHNOLOGY By James H. Krieger Technology Editor
Toward a science policy A great deal of rhetoric has piled up over the past few years bemoaning the current sorry state of federal funding for science. Unfortunately the negative quality of the rhetoric hasn't been notably productive. It is thus heartening to hear something of a shift in attitudes. To be sure, a good bit of what is being said is simple griping. But the scientific community now seems at a point of accepting the situation that exists and attempting to formulate positive approaches for living with it. This attitude is underscored by some of the remarks at a recent symposium on the crisis in federal funding of science held during the annual meeting of the National Academy of Sciences. The current state of federal funding for science is a sorry o n e crisis, chronic illness, or whatever words are used to describe it. It seems very unlikely to change for quite some time. With present public attitudes toward science being as negative as they are, with the public highly resistant to higher taxation, and with intense competition among social programs for funds, legislators aren't likely to respond to the vague pleas they have been hearing from the scientific community. A major problem for science funding is, as stated by Texas Instruments' Patrick E. Haggerty, that science by its Very nature is open ended. Knowledge can be expanded infinitely, and the consequences of any given project aren't concretely foreseeable. Thus, unlike technology, which begins with the end that is to be achieved, it isn't possible to justify support of science on the basis of concrete objectives. This being the case, Mr. Haggerty maintains, support must be justified on a "level of effort" basis. Mr. Haggerty, a member of the President's Science Advisory Committee studying science policy, is one of several calling on the scientific community to help formulate a policy of support for science. Level of effort funding, he points out, requires that such a policy be established, both to set the level at which science is to be supported and then to defend that level of support against the inevitable encroachment of other more definable needs. What considerations involved in establishment of a national science policy need study? Mr. Haggerty lists a number of them. Science policy should probably relate the level of support for science to the gross national product. Expenditures for science around the world show a reasonable correlation with GNP—the wealthier the nation, the proportionately higher the expenditures for science. The reverse correlation—the higher the science expenditures, the higher the GNP—is difficult to establish, however, since high expenditures for science are comparatively recent. In any event, the level of financial support established by a national science policy can't be based simply on asking for more money for each scientific discipline by the members of that discipline. Among other considerations, a science policy should recognize the differences between science and technology but provide for a loose coupling. It should identify and take into account the relationship between science and the education and number of scientists. Not least, to be truly a national policy, it must be based upon proposal and support by the President and discussion, evaluation, and modification by Congress. Whatever a national science policy specifies and however it emerges, it seems reasonable to expect, as some have suggested, that it will have to speak for science as a whole. The public tends to see science as a monolithic entity, making little distinction among chemistry, physics, biology, and the other disciplines. Consequently, the first job for the scientific community is to set up its own priorities internally so that it can speak to legislators and the public with a single voice.
MAY 4, 1970 C&EN
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