Thermal degradation of foamed polymethyl methacrylate in the expendable pattern casting process |
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Authors: | S Mehta S Shivkumar |
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Affiliation: | (1) Department of Mechanical Engineering, Worcester Polytechnic Institute, 01609-2280 Worcester, MA, USA |
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Abstract: | The thermal degradation of foamed polymethyl methacrylate (PMMA) patterns in the expendable pat-tern casting process has been
studied. Various physical transitions that may occur during the degradation of PMMA have been determined using scanning electron
microscopy, differential scanning calorimetry, and thermogravimetric analysis, and the effects of polymer density on the degradation
characteristics have been investigated. The results indicate that, when exposed to elevated temperatures, the polymer beads
collapse at about 140 to 200 °. The collapsed beads melt at 260 ° and begin to volatilize. Peak volatilization temperatures
are on the order of 370 °. The end temperature for volatilization is between 420 and 430 °. The initial density of the polymer
does not have a significant effect on the transition tem-peratures associated with degradation. |
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Keywords: | EPC process full mold process lost foam process PMMA polymethyl methacrylate thermal degradation |
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