Wet adhesion testing of latex paint top coats on old alkyd resin paint - by moving loaded test needles across the wet surface of painted test strips, using special test appts.

摘要

Wet adhesion testing of topcoats on old paints, esp. latex paint on old alkyd resin paint involves wetting one or more test strips of old paint (basecoat) and topcoat, applied to test substrate(s) and arranged side by side, and subjecting the surface of the strip(s) to the action of test needles which are moved over the surface at the same speed by mechanical means, with the same or different contact force or pressure (after or during wetting). Also claimed is an appts. for carrying out the process, comprising a base frame, stand or plate (I) with test substrates (2) coated with paint strips (3) affixed thereto, a bridge-like mounting (4) with a common shaft (5) for rocker arms (6) fitted with holders (7) (of the same or different contact wt. or pressure) for test needles (8), and a movable wetting device (9) beneath the rockers and behind the needles. Pref. the surface of each test strip is wetted for 1-168 (pref. 6-24) hrs.; the old basecoat is first subjected to a brief weathering process; the latex topcoat is 5-500 (pref. 10-150) microns thick and is dried for 1-14 (pref. 3-7) days at 5-50 (pref. 18-25) deg.C before wetting; the wetting device (9) consists of moisture-holding material, pref. strips of felt or woven fabric, or board covered on both sides with cloth to absorb the wetting agent; the needles (8) have a hardened ball point as the indentor, and the substrate(s) consists of strips of glass, wood or paint-resistant plastic. USE/ADVANTAGE - For testing the adhesion of water-based paints to old resin-based paint under wet conditions, e.g. to determine the resistance of such combinations to rain or condensation. The test can be carried out for any desired period of time with various needle loadings, thus making it possible to determine the time at which loss of adhesion occurs and the state of adhesion at a certain time.