PPG SigmaDur 550 – High-Performance Polyurethane Finish for Extreme Weathering

PPG SigmaDur 550 is a two-component, aliphatic acrylic polyurethane finish engineered for outstanding durability and long-term colour retention in harsh atmospheric environments. Curing at temperatures down to -5°C (23°F) and fully resilient to UV exposure, it offers a non-yellowing, non-chalking finish ideal for demanding architectural, industrial and marine structures.

With availability in thousands of colour options including RAL, BS and NCS systems, SigmaDur 550 provides exceptional design flexibility. It can also be recoated an unlimited number of times, even after extended weather exposure, making it ideal for long lifecycle maintenance programs.

Trusted globally, SigmaDur 550 is notably used on the exterior of the Padma Multipurpose Bridge in Bangladesh, showcasing its proven performance in extreme climates.

Key Features:

• Two-component aliphatic polyurethane finish

• Available in RAL, BS, NCS & custom colours

• Excellent colour and gloss retention

• Non-yellowing, non-chalking finish

• Cures in low temperatures down to -5°C (23°F)

• Resistant to splash of mineral & vegetable oils, paraffins & mild chemicals

• Unlimited recoatability, even after long atmospheric exposure

• Smooth application properties by spray or roller

• Designed for high-performance architectural, industrial & marine use

Surface Preparation

Substrate conditions
• Previous coat (epoxy or polyurethane) must be dry and free from any contamination
• Previous coat: surface should be sufficiently roughened if necessary
Substrate temperature and application conditions
• Substrate temperature during application at -5°C (23°F) is acceptable; provided the substrate is free from ice and dry
• Substrate temperature during application and curing should be at least 3°C (37°F) above dew point
• Relative humidity during application and curing should not exceed 85%
• Should condensation on the surface occur during, or soon after application, this could result in colour and gloss change

Technical Data

Pot life
5 hours at 20°C (68°F)
Note:
- See ADDITIONAL DATA – Pot life

Spreading rate and film thickness
DFT Theoretical spreading rate
50 µm (2.0 mils) 11.0 m²/l (441 ft²/US gal)
60 µm (2.4 mils) 9.2 m²/l (368 ft²/US gal)
75 µm (3.0 mils) 7.3 m²/l (294 ft²/US gal)

Directions for Use

Mixing ratio by volume: base to hardener 88:12 (7.33:1)
• The temperature of the mixed base and hardener should be above 10°C (50°F), otherwise extra thinner may be
required to obtain application viscosity
• Thinner should be added after mixing the components
• Adding too much thinner results in reduced sag resistance

Air spray
Recommended thinner
THINNER 21-06
Volume of thinner
3 - 5%, depending on required thickness and application conditions
Nozzle orifice
1.0 - 1.5 mm (approx. 0.040 - 0.060 in)
Nozzle pressure
0.3 - 0.4 MPa (approx. 3 - 4 bar; 44 - 58 p.s.i.)

Airless spray
Recommended thinner
THINNER 21-06
Volume of thinner
3 - 5%, depending on required thickness and application conditions
Nozzle orifice
Approx. 0.43 – 0.48 mm (0.017 – 0.019 in)
Nozzle pressure
20.0 MPa (approx. 200 bar; 2901 p.s.i.)

Brush/roller
Recommended thinner
THINNER 21-06
Volume of thinner
0 – 5%

Cleaning solvent
• THINNER 90-53

Data Sheets

SigmaDur 550 TDS

SigmaDur 550 Base MSDS

SigmaDur 550 Hardener MSDS