Post on 20-Jan-2016
Knot test developmentCEN/TC 139/WG2 N 348
Peter Svane
Coating Consultancy
Copenhagen
Contribution to knot test development
• Starting point Doc. N.303
• Try test method
• Is an internal standard useful?
Coating systems
• 9 WB systems (primer + acrylic paint)
• SB Polyurethane paint (Internal reference)
Exposure time in QUV
Days exposure in QUV - Delta E for Primer 1
0
2
4
6
8
10
12
14
16
Del
ta E
1 day
2 days
3 days
A - acrylic B - alkyd/acrylic E - long oil alkyd F - polyurethane
Knots
B-knots vs. C-knotsAverage. B- vs. C-knot - primer 1 - 3 days in QUV
0,0
5,0
10,0
15,0
20,0
25,0
Del
ta E
B
C BC
B
C
BC
A - acrylic B - alkyd/acrylic E - long oil alkyd F - polyurethane
B- vs. C-knots
0,0
2,0
4,0
6,0
8,0
10,0
12,0
14,0
16,0
0 1 2 3 4 5 6
Del
ta E
B-knots
C-knots
System A
Polyurethane
0,0
2,0
4,0
6,0
8,0
10,0
12,0
0 1 2 3 4 5 6
Del
ta E
C
B
C- vs. B-knots
Time between machining and coating
12,2
8,7
5
6,6
0
2
4
6
8
10
12
14
0 2 4 6 8 10 12 14 16
Døgn
Del
ta E
Shellac or not
0,0
2,0
4,0
6,0
8,0
10,0
12,0
0 1 2 3 4 5 6
Del
ta E
K
K
K K
K
B
BB
B
BShellac
No shellac
Gruppe 5. PU vs. acrylic
0,0
2,0
4,0
6,0
8,0
10,0
12,0
0 1 2 3 4 5 6
Del
ta E
K
KK
K
K
BB
B
B
B
PU
Acrylic
”B-knots”
”C-knots”
Reference
Test system
Matched panels
Suggested setup using matched panels and an internal reference coating
Colour measurement on knots"Worst" vs. mean
0,0
2,0
4,0
6,0
8,0
10,0
12,0
14,0
16,0
19 B 19 K 78 B 78 K 79 B 79 K 164 B 164 K 165 B 168 K
Del
ta E
"worst"
Coating system A
"mean"
Primer 1 vs. PU
0,0
2,0
4,0
6,0
8,0
10,0
12,0
14,0
16,0
1 2 3 4 5 6
Del
ta E
PU
Acrylic
Primer 3 vs. PU
0,0
2,0
4,0
6,0
8,0
10,0
12,0
14,0
16,0
1 2 3 4 5 6
Del
ta E
PU
Acrylic
Primer 4 vs. PU
0,0
2,0
4,0
6,0
8,0
10,0
12,0
14,0
16,0
1 2 3 4 5 6
Del
ta E
Acrylic
PU
Primer 5 contra PU
0,0
2,0
4,0
6,0
8,0
10,0
12,0
14,0
16,0
1 2 3 4 5 6
Del
ta E
PU
Acrylic
Comments
• Conditioning: 50 %RH → 65 %RH• Weather-Ometer → QUV (?)• Panel dimensions acc. to exposure apparatus• Black panel temp. 60 °C → 40 °C (?)• Time from machining to coating strongly influences
staining• Time from machining to coating: 2 weeks• Staining should be measured as the worst
discolouration on a knot• Internal reference concept works, but is it
worthwhile?
Consequences
• Doc. N 303 revised
• Present version is N 341
• Further experiments
Primer 6 vs PU
0,0
2,0
4,0
6,0
8,0
10,0
12,0
14,0
16,0
Del
ta E
Primer 6
PU
Primer 7 vs PU
0,0
2,0
4,0
6,0
8,0
10,0
12,0
14,0
16,0
Del
ta E
P
Primer 7
Primer 8 vs PU
0,0
2,0
4,0
6,0
8,0
10,0
12,0
14,0
16,0
Del
ta E
Primer 8
PU
Primer 9 vs PU
0,0
2,0
4,0
6,0
8,0
10,0
12,0
14,0
16,0
Del
ta E
PU
Primer 9
Comments II
• Graphs for test systems and references have the same shape. Often however one knot gives a much different discolouration
• No influence from the type of knot (“B-” or “C-knot”).
• Whether the concept of using an internal reference is useful calls for statistic evaluation
Statistic evaluation
• Ranking according to draft 927-7 (N341):
9 = 6 = 4 = 2 = 1 < 5 < 3 = 7 < 8 9 < 1
• Ranking with internal reference included:
9 = 4 = 6 = 1 = 2 < 5 < 7 = 3 = 8
6 < 2 7 < 8
Conclusion
• Draft EN 927-7:
• Large variation between individual test panels
• Inclusion of an internal standard apparently does not improve discrimination
Suggestion
• Test procedure should be polished
• Round Robin on draft EN 927-7
• Maybe more test panels