An optical device to measure in‐line residence time distribution curves during extrusion

Abstract

This paper proposes a setup for in‐line measurement of residence time distribution (RTD) curves during extrusion. The detection system is composed of a slit die with transparent borosilicate glass windows fixed at the extruder exit, an optical arrangement with an incandescent light microbulb with fixed luminescence, and a Light Dependent Resistor (LDR) photocell of CdS. As the tracer passes through the light path, the reduction in the transmitted light intensity is followed by changes in the voltage induced by the photocell to an electric circuit. The signal is collected by an external interface and sent to a computer. Software acquires the data, does all calculations, and presents all curves and calculated variables to the monitor. The validation of the system was done by checking for data reproducibility and linearity with tracer concentration. The response of the LDR sensor with respect to the concentration of the tracer was calibrated using a set of slight dark film, obtaining a logarithmic relationship. Thus the signal enhances any disturbance, if present, particularly in the tail‐region of the curves. Measurements were taken from a Werner‐Pfleiderer ZSK 30 twin‐screw extruder equipped with K‐Tron gravimetric feeders operating with various screw speeds, feeding rates and screw configurations. In this last case, the presence of kneading elements was taken into account.

Evaluation of the structure of polypropylene/montmorillonite nanocomposite by in‐line light extinction and color measurements during multiple extrusions

“…This work applies an in‐line method to monitor the efficiency of the tactoids' dissaglomeration/exfoliation of polypropylene (PP)/clay nanocomposites during multiple extrusions. The optical detector applied [4–10] measures in real time the transmitted light intensity producing a signal (in V ) that ranges from a minimum set value called baseline ( V 0 ), measured during the polymer matrix flow without the disperse phase, to a maximum value, called saturation value ( V s ), achieved when the light path is totally blocked. When the radiation interacts with the disperse phase light extinction (scattering plus absorption) occurs, reducing the transmitted light intensity, which is measured continuously by the detector.…”

“…When the radiation interacts with the disperse phase light extinction (scattering plus absorption) occurs, reducing the transmitted light intensity, which is measured continuously by the detector. In a previous work [5], we have stated that the attenuation factor ( T ) due to the presence of the disperse phase is directly related to the normalized detector's signal ( V n ). In a polymer/clay compound the clay tactoids can be detected because their sizes are in the range of producing light extinction.…”

“…Thus, the detector's signal is proportional to the clay fraction that has not been disagglomerated/exfoliated during the melt compounding [11]. To quantify the level of clay particles still present in the PP/montmorillonite (MMT) clay nanocomposites after melt processing the detector response is normalized ( V N ) according to earlier works [4–10, 12–14].…”

Método Simples Para Determinar Distribuição De Tempo De Residência De Polímeros Em Extrusora a Partir De Medidas De Luminância

“…Diferentes artigos têm sido publicados, propondo métodos sofisticados para obter a RTD de processos de extrusão [8][9][10][11]. No entanto, estes procedimentos sugeridos requerem, em geral, equipamentos ou programas caros e, ainda, podem exigir sistemas de montagem complicados, tornando-os extremamente desvantajosos.…”

Factorial design to quantify the influence of extrusion parameters in the mean residence time

“…Canevarolo and Santos [23] and Mélo and Canevarolo [8,22] developed a detection system based on turbidimetry, where visible light extinction is used to infer the concentration of a tracer in a RTD experiments. The detector was coupled at the exit of an extruder and the tracers used were inorganic and organic pigments, others polymers and reactive systems.…”