Klipsun Magazine, 1989, Volume 20, Issue 03 - March

https://cedar.wwu.edu/klipsun_magazine/1103/thumbnail.jp

Klipsun Magazine, 1989 - April

https://cedar.wwu.edu/klipsun_magazine/1101/thumbnail.jp

Near infrared curing of high performance coil coatings.

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

Near infrared curing of high performance coil coatings.

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

Optimization of Near Infrared Cured Polyester/Melamine Coil Coatings by the Use of Near Infrared Absorbing Primers

Near Infrared (NIR) radiative curing is a fastthermal curing technology used to cure 25 micron polyestermelamine industrial coil coatings on galvanized steel substrate.The cure is optimized when the top coat is relatively transparentto NIR and with most NIR absorption taking place at thesubstrate surface. In this study UV/Vis/NIR spectroscopy andlab scale curing trials with a white top coat were used to showthat absorption in the bottom most layers of the coating systemcan be taken a stage further by the addition of NIR absorbingpigment to the primer layer. The results show energy efficiencybenefits for NIR cure by increasing the amount of incidentradiation absorbed without altering the colour properties of thecoating. A similar smaller benefit is also evident with aconventional convection cure

Pressure dependent conduction of individual multi-walled carbon nanotubes: the effect of mechanical distortions

Multi-walled carbon nanotubes (MWCNTs) show an oscillation in electrical resistance (from I–V measurements) during mechanical distortion in which peak separation is inversely correlated with the diameter of the MWCNTs. These results provide the first experimental support of the theoretical prediction that distortion causes Van Hove singularities and Dirac cones in MWCNTs to misalign and cause the opening of the band gap, and suggest that when fabricating contacts for CNTs for device applications, the pressure caused by the contact deposition method must be taken into account for manufacturing devices with consistent properties

Solvent-free microwave-assisted synthesis of tenorite nanoparticle-decorated multi-walled carbon nanotubes

Copper-decorated carbon nanotubes (CNTs) have important applications as precursors for ultra-conductive copper wires. Tenorite-decorated CNTs (CuO-CNTs) are ideal candidate and are currently used in laborious processes. For this reason, we have developed a facile and scalable method for the synthesis of CuO-CNTs from copper acetate. It was found that the optimal loading of copper acetate onto the CNTs was 23.1 wt% and that three 1-minute microwave treatments were sufficient for the decomposition of copper acetate to copper oxide. The loading of copper oxide onto the nanotubes was confirmed using X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy and thermogravimetric analysis. The materials were characterised using X-ray diffraction and scanning electron microscopy

Studying Individual Differences in Language Comprehension: The Challenges of Item-Level Variability and Well-Matched Control Conditions

Translating experimental tasks that were designed to investigate differences between conditions at the group-level into valid and reliable instruments to measure individual differences in cognitive skills is challenging (Hedge et al., 2018; Rouder et al., 2019; Rouder & Haaf, 2019). For psycholinguists, the additional complexities associated with selecting or constructing language stimuli, and the need for appropriate well-matched baseline conditions make this endeavour particularly complex. In a typical experiment, a process-of-interest (e.g. ambiguity resolution) is targeted by contrasting performance in an experimental condition with performance in a well-matched control condition. In many cases, careful between-condition matching precludes the same participant from encountering all stimulus items. Unfortunately, solutions that work for group-level research (e.g. constructing counterbalanced experiment versions) are inappropriate for individual-differences designs. As a case study, we report an ambiguity resolution experiment that illustrates the steps that researchers can take to address this issue and assess whether their measurement instrument is both valid and reliable. On the basis of our findings, we caution against the widespread approach of using datasets from group-level studies to also answer important questions about individual differences

Aqueous electromigration of single-walled carbon nanotubes and co-electromigration with copper ions

The electromigration behaviour of raw and acid purified single walled carbon nanotubes (SWCNTs) in dilute aqueous systems (0.0034 mg mL−1), in the absence of surfactant, with the addition of either 0.85 M acetic acid or 0.1 M CuSO4, was evaluated using a 2-inch copper cathode and either a 2-inch copper or 0.5-inch platinum anode. The results showed that the electromigration of raw SWCNTs (with a high catalyst residue) in the presence of CuSO4 resulted in the formation of a Cu-SWCNT composite material at the cathode. In contrast, acid purified SWCNTs were observed to diffuse to a copper anode, creating fibrillated agglomerates with “rice-grain”-like morphologies. Upon acidification with acetic acid (or addition of CuSO4) the direction of electromigration reversed towards the cathode as a result of coordination of Cu2+ to the functional groups on the SWCNT overcoming the inherent negative charge of the acid purified SWCNTs. The result was the co-deposition of SWCNTs and Cu metal on the cathode. Addition of 0.005 M EDTA sequesters some of the Cu2+ and resulted in the separation of metal decorated SWCNTs to the cathode and un-decorated SWCNTs to the anode. The resulting SWCNT and Cu/SWCNT deposits were characterized by Raman spectroscopy, XPS, SEM, EDS, and TEM