Urethane 1A33 LOF

HumiSeal® 1A33 LOF conformal coating is:

  • polyurethane conformal coating
  • suitable for general printed circuit board applications.
  • single component
  • specially formulated using reduced odour and low toxicity solvent, making it ideal for use in many situations.

Similar to other Humiseal Polyurethane coatings, 1A33 LOF provides high levels of physical and chemical protection and is supplied in a convenient 1 part solvent system, which can be cured easily. After complete cure, the properties of HumiSeal® 1A33 LOF and other HumiSeal® 1A33 products are comparable.

HumiSeal® 1A33 LOF contains no free isocyanates, toluene or xylene, and is RoHS Directive 2015/683 and RoHS 2 compliant.


Product Viscosity, CPS Solids Content % Density, g/cm3 VOC, g/L
1A33 LOF 130-260 42-47 0.90 ± 0.04 488
1A33 LOF PB65 60-75 40-44  0.87 ± 0.02 505

Conformal coatings can be successfully applied to substrates that have been cleaned prior to coating and also to substrates assembled with low residue, ‘no clean’ assembly materials. Users should perform adequate testing to confirm compatibility between the conformal coating and their particular assembly materials, process conditions and cleanliness level. Please contact Humiseal for additional information.


A controlled rate of immersion and withdrawal (5-15 cm/min) will further ensure even deposition of the coating and ultimately a uniform film. During the application,  evaporation  of  solvent causes an increase in viscosity  that should be adjusted by adding small amounts of Thinner. Viscosity in the dip tank should be checked regularly, using a simple measuring device such as a Zahn or Ford viscosity cup.


HumiSeal® 1A33 LOF Pre-Blends are available which can be sprayed using conventional spraying equipment. Spraying should be done in an environment with adequate ventilation so that the vapour and mist are carried away from the operator. The specific pre-blend and spray pressure will depend on the specific type of spray equipment used and operator technique.


HumiSeal® 1A33 LOF Pre-Blends are available which may be brushed onto surfaces. Uniformity of the film depends on specific pre-blend chosen and operator’s technique.


HumiSeal® 1A33 LOF should be stored away from excessive heat or cold, in tightly closed containers. HumiSeal® products may be stored at temperatures of 0 to 35°C. Prior to use, allow the product to equilibrate for 24 hours at a room temperature of 18 to 32°C.


Application of HumiSeal® Conformal Coatings should be carried out in accordance with Local and National Health and Safety regulations. The solvents in HumiSeal® 1A33 LOF and its Pre-Blends are flammable. Material should not be used in presence of open flame or sparks. Use only in well-ventilated areas to avoid inhalation of vapours or spray. Avoid contact with skin and eyes.

Consult SDS prior to use.

Density, per ASTM D1475 0.90 ± 0.04 g/cm³
Solids Content, % by weight per Fed-Std-141, Meth. 4044 44.5 ± 2.5 %
Viscosity, per Fed-Std-141, Meth. 4287 195 ± 65 centipoise
VOC 488 grams/litre
Recommended Coating Thickness 25 – 75 microns
Drying Time to Handle per Fed-Std-141, Meth. 4061 45 minutes at 25˚C
Recommended Thinner Thinner 904, 600
Recommended Stripper HumiSeal® Stripper 1063
Shelf Life at Room Temperature, DOM 12 Months
Thermal Shock, 50 cycles per MIL-I-46058C -65°C to125°C
Coefficient of Thermal Expansion – TMA 193 ppm/°C
Glass Transition Temperature – DSC 26°C
Modulus – DMA 27.2 MPa
Flash point 22.5˚C *estimated
Dielectric Withstand Voltage, per MIL-I-46058C >1500 volts
Dielectric Breakdown Voltage, per ASTM D149 7500 volts