Abstract: The dielectric slit die is an instrument that is designed to measure electrical, rheological, ultrasonics, optical and other properties of a flowing liquid. In one application, it is connected to the exit of an extruder, pump or mixing machine that passes liquefied material such as molten plastic, solvents, slurries, colloidal suspensions, and foodstuffs into the sensing region of the slit shaped die. Dielectric sensing is the primary element of the slit die, but in addition to the dielectric sensor, the die contains other sensing devices such as pressure, optical fiber, and ultrasonic sensors that simultaneously yield an array of materials property data. The slit die has a flexible design that permits interchangeability among sensors and sensor positions. The design also allows for the placement of additional sensors and instrumentation ports that expand the potential data package obtained.

Abstract: A method and apparatus for measuring the temperature of a liquid medium are disclosed. In accordance with the present invention, a liquid medium containing a fluorescent dye is provided. The fluorescent dye is chosen to exhibit a first fluorescence intensity at a first wavelength and a second fluorescence intensity at a second wavelength, wherein the temperature of the liquid medium may be determined in accordance with a predetermined temperature function of the first fluorescence intensity and the second fluorescence intensity. The method of the invention comprises the steps of measuring the fluorescence intensities at the first and second wavelengths; and determining the temperature of the liquid medium in accordance with the predetermined temperature function. The apparatus comprises means for measuring the first and second fluorescence intensities, and means for determining the temperature of the liquid medium in accordance with the predetermined temperature function.

Abstract: A method and apparatus for monitoring the crystallinity and shrinkage of a olymeric resin during molding in which light is introduced into the mold cavity, from an optical fiber through a light permeable window, transmitted through the resin in the mold, reflected from the opposite side of the mold, collected again by the optical fiber sensor, and the attenuation of the light is analyzed to detect mold filling, the onset of polymer crystallization, and separation of the polymeric material from the mold wall due to shrinkage, which separation also produces the geometry of an interferometer which can be used to detect shrinkage and to measure the rate of shrinkage by counting the minima of interference fringes.

Abstract: A method is provided for measuring the onset of polymer solidification, i phase transitions from liquid to crystal or liquid to glass, during injection molding to detect characteristic fluorescence radiation from a dye which has been doped into the polymer at very low concentration. The method involves the use of a calibration relationship between the fluorescence intensity and temperature of the doped polymer in order to determine distinct features which characterize the onset of solidification.

Abstract: A method of measuring fluid properties of a polymer melt, undergoing shear and/or extensional flow which utilizes fluorescent anisotropy. The method utilizes a polymeric chromophore which includes a bifunctional anthracene that is covalently bonded to polybutadiene. The invention also involves an optical probe which is designed to be inserted into existing temperature and/or pressure probe ports in processing equipment. The probe includes a rotatable polarizer and emission collection fibers.

Abstract: Accurate dynamic pressure data in a changing thermal environment is obtained through the use of a pressure gage formed from polyvinylidene fluoride (PVDF) polymer material. The temperature compensation pressure gage has three major elements: an active PVDF transducer which obtains remote pressure readings which are uncorrected for thermal effects; a thermocouple having a short rise time allowing an output thermal signal which dynamically responds to changing thermal conditions; and a compensation amplifier circuit receiving the uncorrected pressure readings and the dynamic thermal signal and producing an output signal representing accurate pressure data which is corrected for changing thermal conditions. Also disclosed are the details of making an active PVDF transducer.

Abstract: An optical sensor containing polarizing optical components measures fluorescence anisotropy of fluorescent dyes. The measurement involves the detection of vertical and horizontal components of fluorescent light. Using Glan-Taylor and Wollaston calcite polarizers, both vertical and horizontal components are collected by separate optical fibers and measured simultaneously using a two-channel photon counter. One application of this sensor is the measurement of molecular orientation during polymer processing. Two sensor head designs are described, one of which fits into the 1/2 inch instrumentation port in polymer processing machines. To carry out process monitoring, a fluorescent dye is mixed with a polymer resin at approximately 10 ppm by weight concentration. Dyes which have geometrical asymmetry in their molecular structure or are covalently bonded to the polymer molecule are usually used. The anisotropy measurement yields information about the orientation of the dye molecule in an oriented medium.