Science/Technology come the problem by using an additive that increases PET's melt viscosity level to the point where the bubbles are entrapped. In a typical operation, the waste PET containers are washed, shredded, ground to a 5-mm particle size, and thoroughly dried. "It's critical that all the water is removed," Smith cautions. "Even trace amounts of moisture can lead to hydrolysis of the polymer chain." The granules, mixed with the melt viscosity index enhancer and a nucleating agent, which acts as a foam stabilizer, go to a standard foam slab extruder unit. There they melt, and Freon 12 is injected into the molten plastic just before it emerges through the extruder at the base, in the same way that foamed polystyrene slabstock is made. The foamed PET that emerges from the die is amorphous. But it converts to a stable, rigid crystalline form within seconds as it cools, at the same time changing color from brown to white. Because PET foam melts at about 260 °C, laminates can be made from it using hot-melt adhesives without damaging its structure. Likewise, it can withstand hot bitumen, thereby allowing slabs of the foam to be used as roofing insulation. Another factor in PET foam's favor is that when it burns, it doesn't emit the dense black smoke that burning polystyrene does. This should be an important advantage in building applications, Smith points out. He acknowledges that use of chlorofluorocarbons for foaming is losing favor because of concern over their adverse effect on the ozone in the upper atmosphere. However, he is confident that when suitable alternatives are developed they will work equally well with recycled PET. There should be no shortage of feedstock. Smith points out that use of PET beverage bottles throughout Western Europe alone now exceeds 330 million lb a year. "Future growth rates are difficult to predict. They will vary from country to country reflecting emerging legislation, which largely is politically motivated," he adds. Dermot O'Sullivan 26
February 12, 1990 C&EN
SOFTWARE/DATABASEUPDATE
• DBMS-Interface Module to Ingres (Molecular Design Ltd., $3000 to $53,000, Circle 301) provides a link between the MACCS-II chemical information system and Ingres (Ingres Corp.), a relational database that runs on DEC VAX/VMS computers. Ingres is used at chemical and pharmaceutical research sites to store and retrieve large amounts of data, such as biological information obtained in safety and efficacy testing of new drugs and chemicals. The new interface module provides MACCS-II users with another relational database option—in addition to IBM's SQL/ DS and DB2 databases and Oracle Development Co.'s Oracle database—for design of integrated scientific information management systems. • Current Contents on Diskette/Engineering, Technology & Applied Sciences (Institute for Scientific Information, $345 annual subscription, Circle 302) is a database that provides access to the contents pages of more than 800 engineering and technology journals published worldwide. The system is updated weekly and is available in versions for IBMs and compatibles, Macintoshes, and NEC 9800s. • Units (MCA Consultants; $99 commercial, $49 academic; Circle 303) makes unit conversions and displays definitions of units and various constants. The program runs on IBM PCs, XTs, ATs, and PS/2s and compatibles. • ATHIAS (Stanford University; $280 commercial, $100 academic; Circle 304), a kinetics program, is a Lotus 1-2-3 worksheet that runs on IBM PCs, XTs, ATs, and compatibles. ATHIAS is an acronym for abiotic transformations of halogenated hydrocarbons in aqueous solutions. The program includes a database of kinetic data on reactions of haloaliphatic compounds in aqueous solution; macros to retrieve rate constants and half-lives of compounds; and
routines to evaluate rate constants and half-lives under different temperature and pH conditions. The current version includes data on 58 compounds; new data can easily be added by the user. • ESR* (Calleo Scientific Software Publishers, $225 to $295, Circle 305) is a first-order anisotropic electron spin resonance program for the Macintosh that simulates both powder and solution ESR spectra. Naturally occurring isotopes for 103 elements are supported. The program permits the user to define lineshape, number of integration steps for solid-angle surface integration, nuclear abundances, spectrometer frequency, linewidths, spectral width, spectral resolution, and other parameters. • CMC-3D (Molecular Design Ltd., $6000 per year, Circle 306) is an electronic three-dimensional database based on "Comprehensive Medicinal Chemistry Drug Compendium" (Pergamon Press), a six-volume work covering rational design, mechanistic study, and therapeutic applications of pharmaceutical compounds. The new database is searchable using MACCS-3D, a module of Molecular Design's MACCS-II system that stores, searches, and retrieves 3-D models and related data. Pharmaceutical researchers can use CMC-3D and MACCS-3D to develop pharmacophores—specific sets of structural, electronic, and geometric parameters that relate to bioactivity.
Literature • 1990 catalog (National Instruments, free, Circle 307) describes line of hardware and software products for scientific and engineering applications, including automated testing, instrument control, data acquisition, process monitoring and control, and lab automation. For information on these items or numbered ads, see Reader Service Card
