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Electromagnetic Processing of Polymers: II. Quantitative Investigations of Microwave Processed Thermoplastics (Microwave Calorimetry)
Published online by Cambridge University Press: 28 February 2011
Abstract
The microwave heatability of various thermoplastic polymers was investigated. The concept of microwave calorimetry was proposed to quantitatively illustrate how viscoelastic behavior controlled microwave heatability. Specifically, heating rate as a function of sample temperature revealed a distinct maximum which was identified as the Tg at 2.45 GHz. The critical temperature, Tc, necessary for rapid microwave heating was identified by drawing a tangent to the heating rate curve and extrapolating to a critical value at zero heating rate. In separate experiments, low frequency (100 kHz) dielectric measurements were made which show the frequency dependence of Tg by means of Arrhenius activation energy plots. In general, the larger the activation energy, the closer the critical heating temperature, TC, was to the Tg determined by DSC. The smaller the activation energy, the further dielectric loss shifted with increased frequency so that Tc was very far from Tg determined by DSC.
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- Copyright © Materials Research Society 1991
Footnotes
Current Address: Institute of Materials Science and Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan, People's Republic of China
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