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Fluorescence temperature measurements: Methodology for applications to process monitoring
Author(s) -
Bur Anthony J.,
Roth Steven C.
Publication year - 2004
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.20081
Subject(s) - materials science , fluorescence anisotropy , fluorescence , die swell , anisotropy , laser induced fluorescence , calibration , capillary action , calibration curve , fluorescence spectroscopy , analytical chemistry (journal) , wavelength , temperature measurement , optics , composite material , optoelectronics , extrusion , chemistry , chromatography , detection limit , statistics , physics , mathematics , quantum mechanics
In previous publications, we described a technique based on fluorescence spectroscopy to monitor resin temperature during processing. The method consists of using optical fiber sensors to monitor fluorescence from a fluorescent dye that has been doped into the processed resin. Temperature is derived from temperature‐induced changes in the fluorescence spectrum. In practice, a temperature calibration function is obtained from the temperature dependence of the ratio of fluorescence intensities at two wavelengths. In this paper, we address several experimental design issues: (a) the supportive role of fluorescence anisotropy measurements to the measuring concept, (b) the experimental setup used for noncontact measurements during capillary rheometry testing, and (c) molecular‐level environmental issues that arise during reactive processing and temperature profiling. We find that fluorescence anisotropy of the dye bis(2,5‐tert‐butylphenyl)‐3,4,9,10‐perylenedicarboximide (BTBP) is independent of shear rate up to 250 s −1 , implying that isotropic orientation of the dye is maintained as the matrix resin undergoes dynamic shear flow, i.e. the calibration function made under quiescent conditions applies to dynamic shear flow conditions. Using this technique in a noncontact application to monitor temperature of the extrudate from a capillary rheometer required an optical design that neutralized the focusing attributes of the cylindrical extrudate. Application to reactive processing is complicated by changes in polarization that accompany the reaction, and, in some cases, produce wavelength shifts in the fluorescence spectrum. We overcome these effects by using a dye that yields a calibration independent of the polarization effects and by averaging over a large dataset to reduce measurement uncertainty. Polym. Eng. Sci. 44:898–908, 2004. © 2004 Society of Plastics Engineers.