Perspectives in Polymer Blend Technology
The subject of polymer blends has been one of the primary areas in polymer science and technology over the past several decades. Judging from publications, patents, major university programs, Ph.D. thesis topics, it continues to maintain significant impor
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PERSPECTIVES IN POLYMER BLEND TECHNOLOGY
L. M. Robeson
Air Products and Chemicals, Allentown, PA, USA
Abstract The subject of polymer blends has been one of the primary areas in polymer science and technology over the past several decades. Judging from publications, patents, major university programs, Ph.D. thesis topics, it continues to maintain significant importance. This will continue, as there are a number of unsolved problems and opportunities. As new areas of interest develop in polymer science, polymer blend technology often becomes an important segment (e.g., electrically conducting polymer blends). This chapter will discuss future opportunities in commercial polymer blends including commodity, engineering, and high temperature polymers. The more recent developments in polymer blend technology will be briefly reviewed and perspectives discussed. These areas include liquid crystalline polymer blends, molecular composites, electrically conductive polymer blends and biodegradable polymer systems. Future trends in the science and technology of polymers blends will be discussed including group contributions and the rapidly emerging area of computational modeling involving computer software employing Monte Carlo, “ab initio”, molecular dynamics, and molecular mechanic approaches. Additional areas briefly discussed include thermoset-thermoplastic blends, coatings, interpenetrating polymer networks, blends in nan-omacromolecular chemistry, organic-inorganics sol-gel systems, polyelectrolyte complexes, and the role of polymer blends in recycling.
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The Past and Present: Relevance to the Future
Although investigated in lesser detail earlier, the science and technology of polymer blends had its emergence in the 1970’s. Many of the basic principles existed prior to that time (e.g., Flory-Huggins thermodynamic principles as well as contributions by Guggenheim and Prigogine). Commercial blends existed for decades before, however the concept of miscibility, phase behavior, and the basic nature of polymer blends was not well understood or appreciated. An initial review of polymer blends [Bohn, 1968] listed only 12 miscible polymer pairs, some of which were minor variations in copolymer structure. The review also noted that UCST (upper critical solution L.A. Utracki (Ed.), Polymer Blends Handbook, 1167-1200. © 2003 Kluwer Academic Publishers. Printed in the Netherlands.
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temperature) would be expected as with solventpolymer mixtures. This, of course, has been well noted not to be the case as the entropic contribution (-T∆S) typically large for solvent-solvent and solvent-polymer mixtures is quite small for polymer-polymer mixtures. Equation of state noncombinatorial entropic effects have been shown to yield LCST (lower critical solution temperature) results [McMaster, 1973]. More important, in many miscible polymer combinations, it is the strong temperature dependence of the enthalpy of mixing (∆Hmix) typical for specific interactions (e.g., hydrogen bonding) that decreases with temperature thus
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