Process monitoring, extrusion

S.E. Barnes, E.C. Brown, M.G. Sibley, H.G.M. Edwards and P.D. Coates, Vibrational spectroscopic and ultrasound analysis for the in-process monitoring of poly(ethylene vinyl acetate) copolymer composition during melt extrusion, Analyst, 130, 286-292 (2005). 

I. Alig, D. Fischer, D. Lellinger and B. Steinhoff, Combination of NIR, Raman, ultrasonic and dielectric spectroscopy for in-line monitoring of the extrusion process, Macromol. Symp., 230, 51-58 (2005). 

Another parameter of interest in the extrusion process is screen pressure, as that has been shown to affect the size of the final pellets as shown in Figure 24 (31). The extruder can be fitted with a suitable pressure transducer to monitor the pressure drop associated with extrusion. One such... 

The final component we need to consider is the instrumentation and control system (Figure 14-10). Good instrumentation is vital to ensure that an extrusion line is operating efficiently and to troubleshoot extrusion problems. Because we cannot see inside the extruder, nor would we leam much even if we could, instrumentation serves as a window onto the process. Monitoring an extrusion system has been compared to monitoring a patient in the hospital you always need to measure vital signs, like blood pressure and body temperature. Likewise, an extrusion line that is not properly monitored can... 

The reactive extrusion is a process demanding precise operation by well-trained personnel. The knowledge of the extruder, compounding and mixing principles, design of screw and temperature profile, local residence time distribution, etc., is required. For optimization of the reactive extrusion in- or on-line process monitoring, control, and data logging are recommended — this imposes further demands on the extruder operator. 

Rohe, T, Becker, W., Krey, A. et al. (1998) In-Une monitoring of polymer extrusion processes by NIR spectroscopy. Journal of Near Infrared Spectroscopy, 6, 325-332. 

The diehead pressure in the extruder determines the output from the extruder. It is the pressure necessary to overcome the resistance of the die. When the diehead pressure changes with time, the extruder output correspondingly changes and so do the dimensions of the extruded product see Fig. 4.1. As a result, when we monitor how the pressure varies with time, we can see exactly how stable or unstable the extrusion process is. 

A. L. Kelly et al., Thermal Optimisation of Polymer Extrusion using In-process Monitoring Techniques, paper submitted for International Conference on Sustainable Thermal Energy Management, Oct. 25-26, Newcastle upon Tyne, UK (2011)... 

Monitoring of many variables. A typical extrusion process requires about 40 to 80 process parameters to be monitored. 

By careful process monitoring we can often detect the effects of wear. The process parameters that are affected by wear are meit temperature, output, and motor ioad. As wear progresses, the quality of the extruded product tends to deteriorate. This may manifest itself as discoloration, streaks, discolored specks, holes, etc. ft is very important to monitor the specific energy consumption (SEC) and specific extruder throughput (SET) because changes in these parameters often correiate with wear. SEC is the ratio of motor power divided by the throughput, ft is the mechanical power consumed per unit mass of plastic. The SEC tends to correiate with the melt temperature. The SEC is normally expressed in kWh/kg. A typicai vaiue of the SEC is 0.25 kWh/hr for extrusion of polyoiefins. 

Markl D, Wahl PR et al (2013) Supervisory control system for monitoring a pharmaceutical hot melt extrusion process. AAPS PharmSdTech 14 1034-1044 Montgomery DC, Keats JB et al (1994) Integrating statistical process control and engineering process control, J Qual Technol 26 79-87... 

Smith-Goettler B, Gendron CM, MacPhail N, Meyer RF, Phillips JX (2011) NIR monitoring of a hot-melt extrusion process. Spectrosc Lett... 

Principles of process control Instrumentation Data acquisition/monitoring Servo control for injection molding Control of extrusion processes Blow molding/parison control SPC/SQC... 

On-line/in-line technology for monitoring extrusion processes, including FTIR microscopy, near-IR spectroscopy and optical microscopy was reviewed [500]. Several reviews describe uFTIR applications to polymers [458,501]. Line map applications of /U.FTIR have been discussed [491]. A recent review [502] refers to a large number of FTIR mi-crospectroscopic studies as an important source of structural and spatial information for polymer-based articles. A monograph describes applications of FTIR microspectroscopy to polymers [393]. ASTM E 334 (1990) describes the general techniques of infrared microanalysis. 

Hansen MG, Vedula S. In-line fiber-optic near-infrared spectroscopy monitoring of rheological properties in an extrusion process. Part I. J Appl Polym Sci 1998 68 859-872. 

Rohe T, Becker W, KdUe S, Eisenreich N, Eyerer P. Near infrared (NIR) spectroscopy for in-line monitoring of polymer extrusion processes. Talanta 1999 50 283-290. 

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