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Near infrared curing of high performance coil coatings. / Cathren Gowenlock

Swansea University Author: Cathren Gowenlock

Abstract

This thesis has investigated Near Infrared (NIR) curing, a fast thermal curing technique for polyester coil coatings used in exterior building applications where fast line speeds are required. The aim has been to further understanding of the NIR cure mechanism. UV/Vis/NIR spectroscopy and curing tri...

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Published: 2014
Institution: Swansea University
Degree level: Doctoral
Degree name: EngD
URI: https://cronfa.swan.ac.uk/Record/cronfa42537
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Abstract: This thesis has investigated Near Infrared (NIR) curing, a fast thermal curing technique for polyester coil coatings used in exterior building applications where fast line speeds are required. The aim has been to further understanding of the NIR cure mechanism. UV/Vis/NIR spectroscopy and curing trials with two types of AdPhos NIR ovens were used to assess the influence of NIR absorbing pigment locus on cure. Firstly, carbon black was removed from red and brown coatings and this resulted in a wider cure window, but re-siting this pigment in the primer layer was unable to maintain coating colour due to top coat opacity. Then the addition of 1 wt.% NIR absorbing pigment to the backing coat was shown to increase top coat PMT by ca. 46°C, thus enabling line speed or oven power settings to be reduced. The convection cure of white coatings with carbon black primers was investigated and a 5 wt.% loading was able to reduce top coat cure time by ca. 3s. In-situ scanning Kelvin probe (SKP) studies showed that rates of coating delamination by cathodic disbondment remained unchanged for primer carbon black loadings of up to 3.5 wt.%. Silver coatings are particularly difficult to cure by NIR, so glass and mica coated flake were investigated as alternatives to aluminium flake, but resulted in coatings with hiding powers reduced by more than 75%. Further formulation suggestions for silver coatings were made, and emissivity and pigment morphology were suggested as potential factors in cure. Finally, NIR pigment additions of up to 10 wt.% to transpired solar collector (TSC) coatings were investigated, and were found to have a much smaller influence on TSC steady state surface temperature than reducing wind speed. An outdoor study of TSC temperature profile revealed that this closely mirrored the incident solar irradiation profile.
Keywords: Materials science.
College: Faculty of Science and Engineering

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