Paint & Coatings Industry - November 2008 - (Page 70)

Self-Crosslinkable Thermosetting Acrylics for Use in Water-Dilutable Coatings stage ranges from 20 to 170 °C, which shows about a 65.51% weight loss. This may correspond to the evaporation of water molecules from the compound having a 32.3% solids content. The second stage of weight loss starts at 170 °C and continues up to 380 °C during which there was a 10.51% weight loss due to the evaporation of free monomer and bound water FIGURE 3 | DSC scan of TSA4 resin. 2 0 Heat Flow (W/g) -2 -4 -6 149.95 ºC 315.1J/g present at that stage. The decomposition temperature of this compound is 465.95 °C. Evaluation of Film Properties Cured films were tested for their optical, mechanical and chemical resistance properties, as per standard test methods viz. gloss at 60° (ASTM D 523-99); scratch hardness (ASTM D 5178); pencil hardness (ASTM D 3363–00); flexibility (ASTM D 4541); impact test (ASTM D 2744); chemical resistance (ASTM D 1308-87); and solvent resistance (ASTM D 5402). Mechanical Properties (a) Scratch Hardness Scratch hardness was determined using an automatic Scratch Hardness Tester (Sheen, UK) having a hardened steel hemispherical point of 1 mm diameter as scratching needle. Results are shown in Table 3. It is clear from the data that films having higher acrylic acid content had high scratch hardness because acrylic acid is known to impart hardness to the films. Consequently, scratch hardness of the films increased from TSA1 to TSA4. -8 146.25 ºC -10 20 40 60 80 100 120 140 160 180 200 Temperature (ºC) (b) Pencil Hardness A cured film strip was drawn under a pencil until a pencil hardness grade was reached to scratch the surface. The coating film was then assigned a hardness value such as H, 2H, 3H etc., signifying the hardness grade using a Pencil Hardness Tester (Sheen, UK). Results of pencil hardness tests are also shown in Table 3. Coating films of TSA3 and TSA4 showed high pencil hardness due to higher acrylic acid content. FIGURE 4 | Thermogram of TSA4 resin. 120 102.82 ºC 25 Deriv. Weight (%/min) 20 65.51% (8.809mg) 100 Weight (%) 80 60 40 20 0 0 100 200 300 400 Temperature (ºC) 10.51% (1.414mg) 15 10 465.95 ºC (c) Crosshatch Adhesion Adhesion was measured by using a Crosscut Adhesion Tester (Sheen, UK). The tester consists of a die made up of 9 parallel blades, 1/16 inches apart and 1 mm long. The die was pressed onto the panel in two directions at right angles to each other. A strip of selfadhesive tape was then stuck over the pattern, left in contact for 10 seconds, and then stripped rapidly by pulling the tape back at an angle of ~120º. The property was rated as good if 95% of squares were not removed. The results were recorded as percentage of squares not removed. All the coating films had good crosshatch adhesion (Table 3). 5 0 -5 600 18.48% (2.484mg) 500 TABLE 3 | Mechanical properties of cured films. Results S.No. 1. 2. 3. 4. 5. 6. 68 Property TSA1 Scratch hardness (g) Pencil hardness Cross-hatch adhesion (%) Flexibility (¼" mandrel) Impact resistance (cm) Gloss at 60 º (%) 1700 3H 100% Pass 103 67 TSA2 1900 3H 100% Pass 95 72 TSA3 2100 3H 100% Pass 90 75 TSA4 2200 3H 100% Pass 85 80 (d) Flexibility Flexibility was carried out on a ¼-inch Mandrel Bend Tester (Sheen, UK). All coating film compositions passed the ¼-inch Mandrel bend test. Therefore, it can be said that the film had reasonably good flexibility; results are shown in Table 3. NOV EMBER 2008 | W W W . P C I M A G . C O M http://WWW.PCIMAG.COM

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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

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