Global Advanced Technologies

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Polyurethane Coatings

Mil –Spec Type UR

Polyurethanes are very versatile coatings. They can withstand harsh chemicals and environmental conditions. Type UR coatings have a durable finish that provides a protective coating for printed circuit boards against water ingress, corrosion, and thermal shock.


Polyurethane coatings, as indicted in MIL-I-46058C, exhibit excellent electrical properties as well as acting as a good barrier against moisture, fungal growth, abrasive force, and chemicals/solvents.

Parts coated with Polyurethanes:

  • PCB- electronics
  • Motors
  • Transformers
  • Relays
  • Solenoids

Why Polyurethane (UR)?

  • Low cost compared to some other coatings
  • Application is by dip, brush or spray
  • Class F temperature rating (160°C / 320°F)
  • Excellent chemical resistance
  • Oil and moisture resistant
  • Very Good for coating circuit boards
  • UV indicator for quality inspection
  • Superior abrasion resistance
  • Excellent adhesion
  • Good flexibility
  • Can be thinned to desired viscosity

Typical Properties of Polyurethane coatings

Note: these can vary considerably from product to product and manufacturer to manufacturer

Hardness, Durometer Value
(ASTM d676-59T)
80A
Specific Gravity 1.07
Tensile Strength, MPa (psi)
(ASTM D412-61T)
20.7 (3,000)
Elongation At Break, %
(ASTM D412-61T)
800
100% Modulus, MPa (psi)
(ASTM D412-61T)
2.8 (400)
Elongation At Break, %
(ASTM D412-61T)
800
Compression Set, %
Method B (ASTM D395)
Method A (ASTM D395)**
45
-
Resilience, %
Rebound (Bashore)
-
Impact Resistance,
Izod notched
J/m (ft.lb./In)
(ASTM D256)
24 Degrees C ( 75Degrees F)
-40 Degrees C (-40 Degrees F)
Flexed
-
Solenoid Brittle Temp.,
Degrees C (Degrees F)
(ASTM D746-57)
Below -80
(Below -120)
Abrasion Index, NBS, %
(ASTM D1630, Nat'l Bureau of Standards Abrader)
110
Tear Strength Split, kN/m (pli)
(ASTM D470)
12.2(70)
Dielectric Withstand 60Hz 1 mil thick 330-630

 Chemical Resistance of Polyurethane Coating

Note: these can vary considerably from product to product and manufacturer to manufacturer

Chemical Rating Chemical Rating
A = EXCELLENT B = GOOD
Acetic Acid, 20% B Ammonium Hydroxide Solutions A
ASTM Oil #1 (70°C/158°F) A ASTM Oil #3 (70°C/158°F) B
ASTM Reference Fuel A A ASTM Reference Fuel B (50°C/122°F) B
Barium Hydroxide Solutions A Borax Solutions A
Boris Acid Solutions A Butane A
Calcium Bisulfate Solutions A Calcium Chloride Solutions A
Calcium Hydroxide Solutions A Carbon Dioxide A
Carbon Monoxide A Castor Oil A
Copper Chloride Solutions A Copper Sulfate Solutions A
Cottonseed Oil A Cyclohexane A
DOWTHERM A B Ethylene Glycol B
Freon - 11 B Freon - 12 A
Freon - 113 A Fuel Oil B
Gasoline B Glue A
Glycerin A n-Hexane (50°C/122°F) B
Hydraulic Oils B Hydrochloric Acid, 20% B
Hydrogen A Isooctane (70°C/158°F) B
Isopropyl Ether B Linseed Oil B
Lubricating Oils B Magnesium Chloride Solutions A
Magnesium Hydroxide Solutions A Mercury A
Mineral Oil A Naphtha B
Naphthalene B Oleic Acid B
Palmitic Acid A Phosphoric Acid, 20%-70% A
Potassium Hydroxide Solutions B SAE #10 Oil (70°C/158°F) A
Seawater A Soap Solutions A
Sodium Hydroxide, 20% A Sodium Hydroxide, 46% B
Soybean Oil B Stearic Acid A A
Sulfuric Acid, 5-10% A Sulfuric Acid, 10-50% B-C
Tannic Acid, 10% A Tartaric Acid A
Tricresyl Phosphate B Trisodium Phosphate Solutions A
Tung Oil B Water (50°C/122°F) A