In this work, temperature profiles, velocity profiles and other parameters such as output rate, pressure, and power consumption were investigated under various processing variables/conditions. The measurements were carried out using an apparatus attached to the output end of an extruder. The effect of processing variables such as screw speed, barrel and apparatus temperatures, die types and die geometries were studied in this work. An investigation was also carded out to study the effect of a breaker plate on the parameters mentioned above. The measurements were also carried out at various points along the length of the apparatus. The technique called Modified CST (Cooled-Stainless Tube), coupled with a temperature measurement sensor (thermocouple mesh) was, used to simultaneously measure the temperature and velocity profiles at multiple points across the diameter of the duct. The measurements were taken using high speed data acquisition equipment (ADU) which was connected to a person"! l computer. The technique used was evaluated and discussed, and it was found that the technique used gives accurate and repeatable measurements at low cost. In order to assist the interpretation of the data generated, rheological and thermal characterisations were carded out on the material used (LDPE10OBWExxon Chemical). Rheological characterisation was carried out using a capillary rheometer and a high shear viscometer. The melt density at a range of temperatures was measured using a melt index tester. The relationship between pressure, density and temperature was studied using a sample of fixed density inside a chamber of fixed volume at various temperatures. Thermal conductivity was measured using a modified Lee's Disc apparatus. Other thermal properties such as melting temperature, the degree of crystallinity, specific heat were determined using Differential Scanning Calorimetry (DSC). Using the specific heat value generated from DSC, combined with thermal conductivity and density value, thermal diffusivity was calculated. Experimentally, it has been found that the temperature profiles varied with the processing variables used. The profiles were related to the melting process inside the extruder, shear heating effects, conduction effects, residence time of the melt inside the equipment and the thermal/rheological characteristics of the polymer used. The velocity profiles, however, did not directly correlate with the temperature profiles, the profiles being related to the effect of the screw speed, screw tip and die entrance. Apart from screw speed, the power consumption was found to be determined by the power required during melting process. It was also found that the flow inside the apparatus duct was steady and laminar, the temperature and velocity profiles developing over the length of the duct.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:493730 |
| Date | January 2000 |
| Creators | Rasid, Rozaidi |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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