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K 2010
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Structural engineering – Polyurethane systems provide protection against all kinds of weather

In structural engineering special polyurethane coating systems provide industrial facilities, bridges, cranes or wind energy plants with durable and effective protection against corrosion, aggressive chemicals, salts and solvents.

In addition, these coatings exhibit a very good adhesion to steel surfaces. On top of that they are easy and fast to apply. These coating systems also show a very good weather and chalking resistance. They keep their color and gloss for a long time.

For polyurethane coatings in structural engineering Bayer MaterialScience recommends a three-layer build-up based on Desmodur® and Desmophen® polyurethane raw materials.

The use of two-component polyurethane coatings based on polyaspartics of the Desmophen® NH product line in combination with aliphatic polyisocyanates of the Desmodur® N range is relatively new. These systems allow the number of coating layers to be reduced, as polyaspartic binders can be applied in thicker films than conventional two-component polyurethane coatings. Moreover, polyaspartics-based coatings only need between 1.5 and 4 hours for the entire curing process at ambient temperature. This way, agricultural, construction and similar equipment can be coated quickly without expensive and energy-consuming stoving lines.

Examples of polyurethane raw materials for structural engineering

For one-component polyurethane coatings

Type
Solids in %
% NCO
on solids
Viscosity
mPas at 23°C
Characteristics
Desmodur® E 1361
MPA/X
TDI
Polyisocyanate prepolymer
61
11.1
500
Resistant against moisture, oils, fuels and aggressive chemicals
Desmodur® E 14
TDI
Polyisocyanate
prepolymer
100
3.3
6800
For highly elastic coatings and sealants with flexible properties
Desmodur® E 21
MDI polyisocyanate prepolymer
100
16.0
5400
Tough elastic, wear resistant
Desmodur® MT
MDI
Polyisocyanate prepolymer
100
16.8
900
Stabilizer for pigmented moisture curing aromatic one component polyurethane coatings

For two component polyurethane coatings

Type
Solids content %
Equivalent
Weight
Viscosity
mPas at 25°C
Characteristics
Desmophen® NH 1220
Asparticesters
100
234
< 100
For tough elastic, lightfast, highly reactive two component polyurethane spray coatings
Desmophen® NH 1420
Asparticesters
100
276
1500
For high solid top coats and solventfree coatings
Desmophen® NH 1520
Asparticesters
100
290
1500
For high solid top coats and solventfree coatings and as reaction partner for Desmodur® N products

Type
Solids
Content %
% NCO
on solids
Viscosity
mPas at 23°C
Characteristics
Desmodur N 75 MPA/X
HDI-Biuret
75
22.0
250
Lightfast, chemical and weather resistant, good mechanical resistance
Desmodur® N 3390 BA/SN
HDI trimer
90
21.8
500
High gloss, good chemical and weather resistance, lightfast, high mechanical resistance
Desmodur® N 3600
HDI trimer
100
23.0
1200
for high solid coatings, high gloss, good chemical and weather resistance, lightfast, high mechanical resistance
Desmodur® N 3900
HDI polyisocyanate
100
23.5
730
Hardener component for weather resistant coating systems

The Desmodur® N grades above might be combined with hydroxy acrylates (like those by our associated company Viverso).

For chlorinated rubber coatings

Molecular weight
Viscosity 1)
mPas at 23°C
Elasticity2)
Iodine color value 1)Characteristics
Pergut® S 5
60000
5
0.5
< 7
For fast curing, weather proof, water and chemical resistant coatings
Pergut® S 10
85000
11
2.4
< 7
For fast curing, weather proof, water and chemical resistant coatings
Pergut® S 20
135000
20
4.5
< 7
Similar to Pergut® S 10, high abrasion resistance
Pergut® S 40
165000
42
4.8
< 7
For fast curing weather, water and chemical resistant coatings, improves drying and resistance against inorganic acids
1) 18.5 % in toluene
2) Erichsen cupping test clearcoat, Pergut®/Desavin®/Xylen (30:3:70), 100min at 90°C


More on Polyaspartics as raw material for corrosion protection

Bayer MaterialScience also offers a range of chlorinated rubber products for corrosion protection with a particularly low Tetrachlorkohlenstoff (C Cl4)
More on Pergut® Chlorinated Rubber

Select starting formulations

RR 5280Moisture curing one-component polyurethane base coat
(Desmodur® E 23)

RR 5282Moisture curing one-component polyurethane intermediate coat
(Desmodur® E 23)

RR 5283Two-component polyurethane top coat, glossy
(Desmodur® N 75)

Take a look at this additional information:

Press Release: ”Binders that pay off”

Presentation given at the European Coatings Show 2007: ”Polyaspartics - Modern binders for highly efficient 2K PUR systems”


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