Powder Coating
Powder Coating
Powder Coating
• Polymerisation
• Chemistries
• chemical reaction
• advantage/disadvantages
• Application
• Melting/Curing process
• Matting
· Addition polymerisation
-A polymerization in which the growth of polymer chains
proceeds by addition reactions between molecules of
all degrees of polymerization (e.g. acrylics)
· Condensation polymerisation
- A polymerization in which the growth of polymer chains
proceeds by condenstation reactions between molecules of
all degrees of polymerization with loss of small molecules
like water. (e.g. polyesters)
· Esterification:
· Hydrolysis:
· Overall:
· Polyacid + Polyalcohol Polyester + Water
· Resin (polyester)
· Crosslinker
· Pigments / Fillers
· Flow agents
· Degassing agents
· Catalysts
Flexibility ++ ++ ++ ++ ++ ++ ++
Flow ++ ++ ++ ++ + ++ ++
adjustability
Exterior -- ++ ++ ++ + ++ ++
durability
Powder ++ + + +/± ± + +
stability
Colour stability
- overbake + ++ + ++ ± ± +
- direct gas + ++ ± ++ + + +
oven
Processing ++ ++ + + ++ ++ +/++
Split-off ++ ++ - ++ ++ + ++
products
Blister-free ++ ++ - ++ ++ + +
layer thickness
Labelling ++ -- ++ ± ++ ++ ++
CH3 CH3
O O
OH + CH CH2 O C O OH O C O
O
CH2
CH3 CH2 HC CH3 CH2 HC
CH2
CH3
OH
O OH
O
R2
R1 O
OH
+ Advantages - Disadvantage
• Price/performance • Outdoor durability
• Flexibility
• Large curing window
• Ease of processing
• Powder stability
• Chemical resistance
O O CH 2
+ CH O
O
OH
H 2C C CH 2
OH
N N HC CH 2
O OH
O
C C
O N O
Carboxylated + TGIC
Polyester (triglycidylisocyanurate)
CH 2
H 2C CH
O
R2
R1 O
OH
+ Advantages - Disadvantage
• Flexibility • Labeling
• Large curing window
• Outdoor durability
• Colour stability
• Processing
• Powder stability
O OH
O
O
OH
+
HO N
OH N OH
O OH
O
HO
O + H2O
N
R1 O R3
+ Advantages - Disadvantage
• Label free • Yellowing tendency
• System cost • Low blister-free layer thickness
• Low curing temperatures • Water sensitivity
• Outdoor durability • Proces sensitivity
• Powder stability
O O O
O
OH
+
OH
O OH O O 0<n<1
O
n
Carboxylated + O O O
Polyester Araldite PT 910 and PT 912, ex-
Vantico
O
R2
R1 O
OH
+ Advantages - Disadvantage
• Well-known chemistry • Xi Labeling
• Excelent exterior durability • Lower cross-link density
• Thick layers • Processing sensitivity
• Colour stability
• e.g. PT 910/Primid
• Primid/Uranox
O O O
O H3C O
OH
+ CH2
OH
R
O OH O n
O
R2
R1 O
OH
+ Advantages - Disadvantage
• No Hazard labelling • Powder stability
• Processing properties (P7200 and P 7300)
• Pigment wetting • Yellowing under extreme test
conditions
HO OH O
+
H O O H
R N N R N C O R O C N
OH
n
R1 O NH
R2
+ Advantages - Disadvantage
• Outdoor durability • Price
• Powder stability • Caprolactam blocked types:
• Flow • Split-off products
• Chemical resistance
EW AV
20 28 35 53 80
10000 250
200
1000
150
100
100
10
50
1 0
0 100 200 300 400 500 600
4 5 0 0
4 0 0 0
3 5 0 0
3 0 0 0
viscosity
2 5 0 0 20°C/min
2 0 0 0
40°C/min
1 5 0 0
1 0 0 0
80°C/min
5 0 0
0 1 2 3 4 5 6 7 8 9 10
Time (min)
10
9
8
Physical stability
7
6
5
4
3
2
1
0
20 30 40 50 60 70
Powder Tg
Influence % cross-linker on Tg
12 70
68
10 66
64 %TGIC
Powder Tg (C)
% cross-linker
8
62
6 60 %PT 910
58
4 56 Resin Tg 64
icw TGIC
2 54
Resin Tg 68
52
icw PT 910
0 50
5 10 15 20 25 30 35 40
Acid Value
1600
1400
1200
Viscosity dPas
1000
800
600
400
200
0
20 40 60 80
resin Tg
• Techniques
• matting agents
• dry blend
• TGIC/PUR
• Freedom of formulation
• Primid
E.g. P870/P833, P873/P835 (optional with DT3329 )
+ gloss setting, mechanical properties
• water split off can give disturbances, gloss variations per layer thickness,
very low gloss is difficult
• PT910
E.g. P2240/P3487 with wax (DT 3329)
+ no splitt off
• moderate mechanicals, powder stability, not very low gloss
• PT910/Primid
+ low gloss possible
• bad mechanicals