| 摘要 |
A powder coating composition comprising a mixture of first and second component powder coating compositions which are separated, preferably widely separated, in a triboelectric reference series indicative of the extent to which powder coating compositions may be distinguishable from one another when electrically charged are described. The mixed powder coating composition is especially suitable for coating articles having recessed portions. A quantitative basis is given for determining the separation of the individual component compositions in the triboelectric reference series, and preferred minimum separation criteria are given. The figure represents a powder coating application gun that was clamped into position such that the gun was pointing directly at the corner of the test piece, with a gun-tip to corner distance of 30 cm. The panel was coated (gun settings: fluidising air 1.0 bar, conveying air 0.6 bar, supplementary air 3. 5m3 hour -1, single corona needle conical baffle nozzle at-50 kV). The weight of the coated piece was recorded, and compared with the uncoated weight of the piece. A range of application trials was carried out for each powder coating mixture until an applied weight of 4.0 grams of powder coating had been achieved. The resulting coated test piece was then stoved to give a cured film (stoving conditions: 10 minutes at 180°C), and reserved for further inspection. For each coated test piece, the degree of penetration of the powder coating into the corner region was visually assessed. In order to remove the subjective nature of an individual visual assessment of the penetration, six people individually assessed the coated test pieces, and ranked the penetration from best to worst. These results were averaged and collated, into four groups from I -Excellent penetration to IV -Poor penetration. |
