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Progress in Plasma Processing of Materials, 1999

ISBN:
1-56700-126-2 (Print)

EXERGY ANALYSIS OF A DC PLASMA SPRAYING OF POLYMER/Al203 COMPOSITE COATING

K. Y. Tufa
Plasma Technology Research Centre (CRTP), Department of Chemical Engineering University de Sherbrooke, Sherbrooke (Quebec) CANADA J1K 2R1

D. Gravelle
Plasma Technology Research Centre (CRTP), Department of Chemical Engineering University de Sherbrooke, Sherbrooke (Quebec) CANADA J1K 2R1

Francois Gitzhofer
Plasma Technology Research Centre (CRTP), Department of Chemical Engineering University de Sherbrooke, Sherbrooke (Quebec) CANADA J1K 2R1

Abstract

DC plasma technology has been used for many years in the spraying of polymers. However, especially for the low melting point polymers, basic exergy analysis shows that a lot of the high availability energy is wasted in the process. Following exergy analysis, a high energy recovery dc plasma torch has been developed and applied to the deposition of > 10 mm thick polymer composites for abrasion resistant protective surfaces. The injection of low cost fillers such as alumina or silica into the hot plasma zone can absorb much heat and cool the plasma, while the polymer powder is injected into the cooler zone downstream. After deposition, the energy absorbed by the fillers can then be transferred within the polymer matrix coating providing for an energy recovery mechanism. The exergy analysis undertaken for this new process concept shows that the availability of the biphasic plasma/Al203 (− 22 + 5 µm) fluid increases with build up of alumina particles feed rate which inturn magnifies the useful exergy efficiency. Coating surface roughness measurements show that without alumina particles, the surface is very rough because the presence of unmelted polymer particles. However, the addition of the alumina decreases the roughness due to the hot filler particles completing the polymer melting process inside the coating.