Abstract

A high energy recovery of 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 in the hot plasma zone can absorb a lot of energy and cool down the plasma whereas polymer powder is injected downstream in a much cooler zone. Indeed, the energy absorbed by the fillers can then be transferred inside the polymer matrix coating allowing an energy recovery mechanism. The result is a composite polymer/ceramic with the following benefits: The shrinking phenomena due to the polymer recrystallisation is eliminated allowing a good coating adhesion, a high polymer/filler throughput can be achieved and the risk of the in-flight polymer combustion is largely reduced. The fillers addition decreases the overall cost of the coating and the type of filler can influence the composite properties. Abrasion resistant composites have been produced with alumina fillers. Medium density polyethylene (MDPE) sprayed with 45 wt % reinforcement as tested on the modified ASTM G-65 apparatus has shown abrasion resistance as good as ultra high molecular weight polyethylene (UHMWPE), which is one of the highest abrasion resistant polymer. In order to understand the abrasion resistance mechanisms, variables in the coating process such as: size of the fillers, polymer injection angles, polymer degradation and composite microstructure have been analyzed.

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