In‐line color monitoring of polymers during extrusion using a charge coupled device spectrometer: Color changeovers and residence time distributions

Abstract

A fiber-optic-assisted, charge-coupled device spectrometer was used to monitor the color of molten polymer concentrates during extrusion. Color coordinates L*, a* and b* were calculated from each of the reflectance spectra as polyethylene color concentrate was replaced by a purge material and as the purge material was replaced by another color concentrate. A method of calculating replacing component residence time distributions and component washout residence time distributions from the spectra was developed and applied. Results with a red and a blue concentrate showed that dimensionless time (time/average residence time) superimposed both residence time distributions and color coordinate variations during changeover from two different extruder screw speeds. X = k S(h) R(h) x(h) d h 780 I, 380 r 780 k x S ( X ) R(X) x(h) AX (11 S(h) R(X) y(X) d hk x S(X) R(X) y(X) AX (2) 380 780 S(X) R(h) %(A) d hk x S(X) R(X) :(A) AX (3) 380where S(X) is the spectral power distribution of the standard illuminant selected, R(h) is the reflectance spectrum of the sample X(X). y ( h ) , Z(X) are the color matching functions for the standard observer selected and k is a constant (1).However, although color can be matched and compared by using the tristimulus values, there are several 356

In‐line measurement of residence time distribution in melt extrusion via video analysis

“…Fluorescence spectroscopy was utilized as well, with tracers such as perylene [17,18] and anthracene [19][20][21][22][23]. Other measurement techniques include UV-vis [24,25], ultrasonic [26,27] and near-infrared (NIR) [5] spectroscopy, NIR chemical imaging [28], and conductivity [6]. In the latter publication, qualitative video analysis was performed to study flow phenomena caused by certain screw elements using glucose syrup with dark-colored spherical particles in a translucent extruder [6].…”

Process monitoring and visualization solutions for hot-melt extrusion: a review

“…Gilmor et al [69] developed an in-line colour monitoring system: the colour of the melt during changeover from one pigmented PE to another was continuously measured directly in an extruder using a fibre-optic-assisted, chargecoupled device spectrometer. The fibre-optic reflection probe was inserted into the die of a single-screw extruder.…”

A Critical Overview of Sensors for Monitoring Polymerizations

“…There are a number of patents regarding fiber probes for specific use in Raman scattering 233, 234. Other areas where fiber‐optics technology has been applied are light scattering,235, 236 IR spectroscopy,237–242 fluorescence spectroscopy,243 UV spectroscopy,244–247 pressure sensing,32, 33, 37, 38 in‐line monitoring of polymer processing,237, 239, 246, 248–251 cure monitoring,215, 243 and in pH sensors 252–256…”