• ultrasonic in-line monitoring of styrene miniemulsion polymerization

    جزئیات بیشتر مقاله
    • تاریخ ارائه: 1392/01/01
    • تاریخ انتشار در تی پی بین: 1392/01/01
    • تعداد بازدید: 458
    • تعداد پرسش و پاسخ ها: 0
    • شماره تماس دبیرخانه رویداد: -
     ultrasonic transmission is a simple, non-destructive method to characterize turbid systems like e.g. emulsions or polymer dispersion. here we use this technique for in-line monitoring of the miniemulsion polymerization of styrene. either the ultrasound attenuation or the velocity signal provides a fingerprint characterizing the reaction process. during the reaction process the sound velocity increases by about 150 m/s and the attenuation coefficient α changes by more than 75%. in the early stage of polymerization the thermoelastic effect dominates α and accordingly α decreases when more and more polymer chains are generated. in this regime the fractional conversion of monomer to polymer x is obtained from a calibration of the α values using gravimetrically determined x data. in the later stage of the process polymer relaxation dominates and αgoes through a sharp maximum when the reaction temperature matches the dynamic glass transition temperature tg,dyn of the polymer/monomer mixture within the droplets. then x can be directly calculated from tg,dyn without calibration only using physical material parameters for the given monomer/polymer system, and the corresponding data are in excellent agreement with gravimetrically determined values.

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