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All statements, technical data, and recommendations expressed herein are based on tests believed to be reliable and accurate. However, APTEK LABORATORIES, INC. gives no warranty,
expressed or implied, regarding the accuracy of this information. It is intended that the buyer and user of these products shall determine the suitability of the information provided for his
specific application, and is responsible for its selection.
APTEK LABORATORIES, INC. shall not be liable for any injury, loss or damage, direct or consequential, arising out of the use or misuse of these products, or of the information given in
Low modulus urethane conformal coating
APTEK 2503-A/B is an unfilled, two component, electrically insulating, transparent, flexible urethane coating
system designed for the encapsulation and protection of electronic devices mounted on printed circuit boards.
For coating applications that require toughness, this system provides a combination of excellent flexibility and
optimum tensile strength/elongation characteristics.
KEY FEATURES AND BENEFITS
• Qualified to Mil-I-46058C, and meets the requirements of SCD 652898 and IPC-CC-830B
• Non-TDI based for safety
• Excellent reversion resistance for good physical stability under high heat and humidity environments
• Tg BELOW -70
C for excellent low temperature cycling, storage and performance
• Excellent substrate adhesion; no primer needed; superior to silicones
• Exceeds NASA outgassing requirements for high vacuum environments
• Fluoresces under black-light (UV) to facilitate QC inspection of coating coverage
• Low viscosity and long work life for spraying or dipping operations
• Complete ancillary product line -- APTEK 2503 Thinner, APTEK Stripper, APTEK 2503R A/B Repair Kit
Mix ratio, parts by weight
Work life, @25
C, 300 gm mass, hours
Tack-free time @85
C, ACO, minutes
2. Work life can be greatly extended by additions of thinner and/or periodical replenishment with freshly mixed
APTEK 2503 A/B.
Unused portion must be blanketed with dry nitrogen or argon and resealed to avoid moisture contamination.
Store @ 15-25
dimer precipitate. The precipitate is not harmful, however, follow instructions listed below for best results.
- Do not shake bottle. If liquid is clear with precipitate on bottom, then decant and use.
- Place unopened Part B bottles (NOTE: do not loosen cap) into an air circulating oven at 30-40
C until clear
- Carefully remove bottles from oven without disturbing contents. To use Part B, decant clear liquid out of bottle
without disturbing the precipitate.
Weigh 100 parts of APTEK 2503 Part A into a clean dry glass, metal, or plastic container and then add 50 parts of
APTEK 2503 Part B. Machine mix on slow speed or hand stir with glass or metal stirrer until complete and
thorough blending is achieved. Care should be taken to avoid any source of moisture contamination or air
entrapment during mix.
Note: For best results and a bubble-free coating, vacuum mixture at less than 10mm Hg for no more than 1
8 hrs. @ 85
5 hrs. @ 100
2 hrs. @ 125
* It is recommended that coated substrates air dry 60 minutes at RT prior to heat cure to allow solvent
evaporation which minimizes chance for bubble formation during heat cure.
Note: As typical with urethane systems, a relaxation/stabilization period of 2-4 days after cure is required before
(values not to be used for specification purposes)
pale yellow to amber
pale yellow to dark amber*
Viscosity @ 20
Shelf life @ 15-25
C and RH <50%,
Months in factory sealed containers
has no effect on any cured properties.
preserve maximum use life, blanket the contents of the containers with dry nitrogen or argon before resealing.
CURED PHYSICAL PROPERTIES
Hardness, Durometer A
Tensile strength, psi
Glass transition temp.,
Thermal coefficient of expansion,
Outgassing @ 10
Evidence of haze
Volume resistivity, @25
Dielectric constant, @1KH
Dissipation factor @1KH
Dielectric strength, 0.003" thick
Insulation resistance, ohms
3.2 x 10
APTEK 2503-A is an unfilled polyol resin containing solvent and is thus considered a flammable liquid and should
be treated with caution. Avoid storage temperatures above 25
C and keep away from flame, sparks, or other
fresh clean water for at least 15 minutes; for skin contact, wash thoroughly with soap and water. If swallowed,
drink at least one pint of water and call a physician. Refer to Material Safety Data Sheet for more details.
APTEK 2503-B is an organic isocyanate containing solvent and is thus considered a flammable liquid and should
in breathlessness, severe coughing, chest discomfort, and irritation of mucous membranes. Avoid skin and eye
contact and use in well-ventilated, hooded area. In case of eye contact, flush profusely with fresh clean water and
contact physician. For skin contact, wash thoroughly with soap and water. If inhaled, move subject to fresh air
and provide fresh water to drink. If swallowed dilute, with at least one pint of water and contact physician
immediately. Refer to Material Safety Data Sheet for more details.
is a registered trademark of Aptek Laboratories, Inc.