A multi-method approach to quality control illustrated on the industrial powder coating process
Industrial powder coating processes offer a unique object of application for Anton Paar Rheometers. Compared to classic coating procedures with liquid materials, powder coating is still a relatively young procedure. Its first industrial applications date back to the mid-1960s and its ever increasing use since then can be mainly attributed to the desire for more environment-friendly coating systems. The Powder Coating process is dependent on the one end on pneumatic conveyance behavior, namely the transport as a dense fluidized powder phase and its associated bulk solid values and, on the other end, on bulk polymer behavior, used to determine and keep constant the curing point at which the applied powder bonds and produces an (ideally) smooth surface. This multivariate process is an ideal object of quality control for MCR Rheometers and two accessories: the Powder Cell and a disposable Plate-Plate Geometry with Peltier-heated hood (P-PTD 200, H-PTD 200). Both processes can be described and predicted by the use of an Anton Paar MCR Rheometer.
Powder coatings are a growing technology with numerous applications. Initially designed to generate coatings displaying a greater resilience than comparable liquid-applied ones, the technique’s current rapid development is essentially driven by the need for more environment-friendly, solvent-free processes. It consists of several processing steps. The powder coating is first fluidized then introduced into the pneumatic conveying system, leading up to the electrostatically-assisted application (via spraying) onto a prepared substrate. The applied coat is then submitted to a heat treatment stage where polymerization takes place and the coating is expected to both bond to the substrate and form a continuous, smooth surface.
This involves rather complex mixtures of powders, including - but not limited to - systems that use two co-polymers along with the catalysts (so-called hybrid coatings) or, as in the simpler case of polyethylene coatings, of polymer mixtures consisting of monomers and Ziegler-Natta catalysts.
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