NEWS OF THE WEEK POLYMER
RESEARCH
PLASTICS MOLDED AT ROOM TEMP Mixing technique could save energy in plastics processing and aid recycling
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LASTICS USUALLY MUST BE
heated to temperatures exceeding 200 °C to make them fluid enough to be ex truded or molded into useful shapes. But a new componentmixing technique makes it pos sible to mold plastics at room temperature [Nature, 426,424 (2003)1. The work, by profes sor Anne M. Mayes and co workers at MIT, could lead to energy savings in industrial plastics processing and could promote plastics recycling. Five years ago, professor Tom Russell's group at the Universi ty of Massachusetts, Amherst, collaborated with Mayes's team to develop "baroplastics" that become disordered more easily under pressure. But in those studies, the pressure-induced transitions were observed at rel atively high temperatures. "Designing materials with the right glass transitions that could exhibit pressure-induced mixing and possibly be processed at room temperature was a fouryear road from there," Mayes says. Glass transition tempera ture (Tg) is the temperature at which polymers change from solid to meltlike. In the new low-temperature baroplastics, a glassy high-T component such as polystyrene is mixed with a rubbery lower Tg component such as poly(«-butyl acrylate). Under pressure, the rubbery component tends to sol vate the glassy one, causing the mixture to melt and flow at much reduced temperatures. The pres sure exerted by some conven tional molding and extrusion equipment is sufficient to make HTTP://WWW.CEN-ONLINE.ORG
the low-temperature baroplastics workable. The researchers demonstrat ed low-temperature processing of block copolymers and poly mers made from two-compo nent core-shell nanoparticles. They concede that block copoly mers "have potential drawbacks as substitutes for today's com modity plastics in that their synthesis is generally more com plex and expensive." However, core-shell nanoparticles are polymerized by free-radical synthesis —the most common type of industrial polymeriza tion—and thus provide better prospects for industrial use. "The ability to process and mold polymeric materials at room temperatures represents a tremendous advance in the fab rication and recycling of plas
ACS
tics," says CraigJ. Hawker of the Center on Polymer Interfaces & Macromolecular Assemblies at IBM Almaden Research Center. "The research represents a nov el and general concept for elim inating the numerous problems associated with thermal degra dation and may find general ap plicability for a wide range of materials." "Honestly, I think it is too early to say how this technolo gy will impact the plastics field, since we still have much to learn about its ad vantages and limita tions," Mayes tells C&EN. "But it seems like there is a lot of op portunity. Pressure-based pro cessing could save significant energy because of the reduced temperatures involved; allow for multiple recycling of plastics giving properties comparable to the virgin materials (since there is no thermo-oxidative degra dation involved); reduce the need for stabilizers and other processing additives; and allow for incorporation of new com ponents, such as biologically de rived or other thermally sensi tive materials."—STU BORMAN
COLD MOLD Mayes and coworkers molded these boxes at relatively low temperature (40 °C) from core-shell particles of polystyrene/poly(n-butyl acrylate) baroplastic (powder in central box).
MIT PHOTO
ELECTIONS
Plans Are Set To Fill ACS Board Vacancy
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he ACS Committee on Nominations & Elections announced last week that Allen J. Bard, Hackerman/Welch Regents Chair and director of the Laboratory of Electrochemistry, Uni versity of Texas, Austin, and Kathleen C. Taylor, retired director of the Materials & Processes Laboratory, General Motors Re search & Development and Planning Center, Warren, Mich., will be candidates in the spe cial interim election being held to fill the ACS Board of Directors vacancy created by the death of Stanley C. Israel, director-at-large (C&EN, Nov. 10, page 13). In accordance with ACS bylaws, additional candidates may be nominated by petition. The deadline for petition candidates for the spe cial interim election is Jan. 9,2004. Petitions Bard Taylor should be sent to the ACS Executive Director, 1155—16th St., N.W., Washington, DC 20036. It is anticipated that the ballots will be mailed to all voting councilors on Jan. 19, 2004, with a deadline for return of Feb. 13.—LINDA RABER
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