Paint & Coatings Industry - November 2008 - (Page 37)

with 16 mm diameter screws and L/D 14. The extrusion temperature was set at 120 °C, the extrusion speed at 200 rpm, and the torque was kept between 75 - 90%. After extrusion, the extruded material was ground by a Retch ZM 100 centrifugal mill and sieved through a Retch Vibro sieve with a mesh of 90 µm. Finally, the powder coatings were sprayed electrostatically onto steel panels (Q-panel S 46) with a GEMA PG1 spraying gun and placed vertically in a UT 6120 hot-air oven from Heraeus. Coatings with a layer thickness of 60 µm were used for evaluation. Evaluation Flow was visually evaluated on coated panels and compared to PCI standards. In addition, the flow was evaluated with a white light interferometer from Veeco. This device is able to rapidly measure a 3D scan of a large surface area (e.g., 2x2 mm2 with a single scan) with a height resolution of a few nanometers and a lateral resolution of 600 nanometers. By using an automatic XY table and appropriate “stitching” software, the interferometer was able to measure even much larger samples (e.g., 10x2 mm2). Coating flexibility was tested via reverse impact, according to test method ASTM D 2794. Coated steel panels were subjected to an impact of 160 inch-pound on the back of the panel. Also ALMg3 panels were coated and cured for 10 minutes in a BYK-Gardner gradient oven between 150 - 250 °C. These panels were subjected to an impact of 160 inch-pound. Gloss and haze were measured at 20° and 60° with the BYK Gardner reflector meter, according to the standard ASTM D 523. Heat resistance was determined by placing a cured panel in the oven at 240 °C for 10 minutes and 220 °C for one hour. Colour differences between an untreated panel and the treated panel were evaluated. Salt spray tests were conducted on a cured panel with a vertical scratch of 1 mm, according to ASTM D 2803. The cured panel was placed in salt spray equipment for 500 hrs. After 500 hrs, the average creepage from scratch was measured. The powder and coating Tgs were determined by differential scanning calorimetry (DSC) at a heating rate of 5 °C/min. TABLE 3 | Typical hybrid formulations with 33 and 50 wt% TiO2. 70/30 Hybrid 70/30 Hybrid 60/40 Hybrid 60/40 Hybrid 33 wt% 50 wt% 33 wt% 50 wt% Pigment Pigment Pigment Pigment 70/30 hybrid resin 60/40 hybrid resin Araldite® GT 7004 Kronos 2310 Resiflow® PV 5 Benzoin 138 59 99 3 1.5 116 50 170 3.4 1.2 118 79 99 3 1.5 99.5 66.5 170 3.4 1.2 FIGURE 2 | Haze of coatings, made with a standard 70/30 and 60/40 hybrid resin and Uralac P 770, P 772 and P 760, versus pigment concentration. 350 300 250 200 150 100 50 0 30 35 40 45 50 Pigment Concentration (wt %) Uralac P 770 55 60 Haze Standard 70/30 hybrid 350 300 250 Haze Uralac P 772 Results Haze Haze values are an indication of the appearance. In general, if the haze value is low the appearance is good; if the haze value is high the appearance is bad. Haze values of the final coatings were measured by the BYK Gardner reflector meter. Haze measurement results are shown in Figure 2 for different pigment concentrations. A comparison between standard res- 200 150 100 50 0 30 35 40 45 50 Pigment Concentration (wt %) 55 60 Standard 60/40 hybrid Uralac P 760 35 PA I N T & C O A T I N G S I N D U S T R Y

Table of Contents Feed for the Digital Edition of Paint & Coatings Industry - November 2008

Paint and Coatings Industry - November 2008 Contents Viewpoint Industry News Calendar of Events Company News Mergers and Acquisitions Names in the News HiTone Resins for Enhanced Pigment Affinity of Powder Coatings New Water-Based Interior Coatings Combine Innovation and Quality With Respect for the Environment Novel, UV-Curable Nanotechnology-Enabled Coatings Highly Weather-Resistant Radiation-Curable Monomers and Oligomers for Exterior Applications Konica Minolta — Sensing Success for Viracon Self-Crosslinkable Thermosetting Acrylics for Use in Water-Dilutable Coatings Paint and Criminal Forensic Science Supplier and Application/Curing Showcases Materials Watch Classifieds Advertiser Index

Paint & Coatings Industry - November 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.