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An infrared temperature sensor has been used to provide real time quantification of the thermal homogeneity of polymer extrusion. The non-intrusive sensor was located in the barrel of a single screw extruder, positioned such that it provided a measurement of melt temperature in the channel of the metering section of the extruder screw. The rapid response of the technique enabled melt temperature within the extruder screw channel to be monitored in real time, allowing quantification of the thermal stability of the extrusion process. Two polyethylenes were used in experiments with three extruder screw geometries at a range of screw speeds. Data generated by the infrared sensor was found to be highly sensitive to thermal fluctuations relating to the melting performance of the extruder screw. Comparisons made with an intrusive thermocouple grid sensor located in the extruder die suggested that the infrared technique was able to provide a similar level of information without disturbing the process flow. This application on infrared thermometry could prove highly useful for industrial extrusion process monitoring and optimization. POLYM. ENG. SCI., 55:1059–1066, 2015. © 2014 The Authors. Polymer Engineering & Science published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers

Ultrasonic technology provides a powerful and noninvasive method of in-process measurement during injection molding and extrusion. Changes in the velocity, attenuation and reflection coefficients of high frequency sound waves can be related to the state and conditions of the materials through which they propagate. The velocity of an ultrasonic wave changes with density and elastic moduli; this allows information on solidification and material properties to be collected during the molding cycle. The time of flight of the wave is a function of velocity and path length. This paper shows that it can be correlated with the residual wall thickness of polymer in the mold during gas assisted injection molding. POLYM. ENG. SCI., 47:1730–1739, 2007. © 2007 Society of Plastics Engineers

Experimental observations of melt temperature profiles and melting performance of extruder screws are reported. A novel temperature sensor consisting of a grid of thermocouple junctions was used to take multiple temperature readings in real time across melt flow in a single screw extruder. Melt pressure in the die and power consumption were also monitored. Three extruder screws at a range of screw speeds were examined for a commercial grade of low density polyethylene. Results showed melt temperature fields at low throughputs to be relatively independent of screw geometry with a flat-shaped temperature profile dominated by conduction. At high throughputs, melting performance and measured temperature fields were highly dependent upon screw geometry. A barrier-flighted screw with Maddock mixer achieved significantly better melting than single flighted screws. Low temperature “shoulder” regions were observed in the temperature profiles of single-flighted screws at high throughput, due to late melting of the solid bed. Stability of the melt flow was also dependent upon screw geometry and the barrier-flighted screw achieving flow with lower variation in melt pressure and temperature. Dimensionless numbers were used to analyze the relative importance of conduction, convection, and viscous shear to the state of the melt at a range of extrusion conditions. Polym. Eng. Sci. 46:1706–1714, 2006. © 2006 Society of Plastics Engineers

In a double-blind study, 90 patients (ASA 1 or 2) received spinal anaesthesia with 2 ml hyperbaric cinchocaine 0.5%, 4 ml hyperbaric bupivacaine 0.5% or 4 ml plain bupivacaine 0.5%. All injections were made in the left lateral position, and the patients turned supine immediately. Hyperbaric bupivacaine produced a significantly faster and a higher dermatomal level of bilateral complete sensory blockade than the other solutions (p less than 0.005 for each). The duration of sensory blockade was significantly longer with plain bupivacaine than with either hyperbaric solution (p less than 0.0005). The intensity of sensory blockade was significantly greater with both bupivacaine solutions than with hyperbaric cinchocaine (p less than 0.05). Onset and intensity of motor blockade were similar with all agents, but motor blockade was of significantly shorter duration with hyperbaric bupivacaine than the other agents (p less than 0.0005). Hyperbaric bupivacaine appears to be the best agent for rapid and intense sensory blockade of intermediate duration. Plain bupivacaine is more appropriate if a longer duration of action but a lower height of blockade are required, and has the advantage of less cardiovascular disturbance.