Tough-Seal 31

Tough-Seal 31 is a tough and durable fast gelling Potting Compound and Sealant with excellent Thermal Cycling Stability.

Tough-Seal 31 Properties

tough-seal label design
  • Fast gelling
  • Low viscosity
  • 400% elongation
  • Shore Hardness: 37A
  • Excellent Thermal Cycling Stability from -40°F (-40°C) to 302°F (150°C)
  • Applications include: automotive and marine sensors, thermistor sensors, wire harness assemblies, underwater lighting, highly engineered motor and control systems

Product Specifications: PC2031AB

Tough-Seal 31 is a tough and durable fast gelling Potting Compound and Sealant with excellent Thermal Cycling Stability. This low viscosity material is self-leveling and flows like maple syrup around intricate electrical components to ensure complete coverage of your entire PCB or electronic assembly.

Tough-Seal 31 has a faster 10-20 minute working time and a Shore Hardness of 37A, which is similar to the hardness of a pencil eraser. Tough-Seal 31 reaches 94% of its full hardness after an overnight cure or with a heat cure of 1 hour at 80°C (176°F). Tough-Seal does not exotherm or shrink during curing, therefore there is no embedment stress induced on the electronic components that could cause damage and failure of the PCB or electronic assemblies. Sensitive electronics can be potted safely with low embedment stress Tough-Seal.

With a high elongation of 400% when fully cured, Tough-Seal 31 maintains exceptional flexibility and thermal cycling stability from –40°C to 150°C (-40°F to 302°F) without pulling back, wilting, or cracking. This ensures a tough seal that will stop moisture or other contaminants from damaging sensitive PCB’s and electronics.

Tough-Seal has very aggressive adhesion to aluminum, making it a perfect choice for potting aluminum housings in LED lighting applications. Tough-seal bonds extremely well with most polymers. For housing and wire insulation materials that are exceptionally difficult to bond to, we offer our KEY PR1200 PRIMER, an aggressive adhesive promoter that is simple to use.

Technical Data Sheet (TDS) and Safety Data Sheet (MSDS)

Tough-Seal Series

Physical Properties

Color, Part A

Off White

Viscosity at 25°C, cP, Part A, (RVT #5, 20 RPM)


Specific Gravityat 25°C, Part A


Color, Part B


Viscosity at 25°C, cP, Part B, (RVT #5, 20 RPM)


Specific Gravity at 25°C, Part B
Density at 25°C, lbs/gal, Part B
Color, Mix
Grey / Black
Viscosity at 25°C, cP, Mix, (RVT #5, 20 RPM)
Specific Gravity at 25°C, Mix
Density at 25°C, lbs/gal, Mix
Mix Ratio by Volume
1A to 2B
Mix Ratio by Weight
57A to 100B
Gel Time at 25°C, Minutes, 100 grams
Shelf Life, Ambient, Part A Bulk (15°C to 35°C)
3 Months
Shelf Life, Ambient, Part B Bulk (15°C to 35°C)
12 Months
Shelf Life, Cold, Part A Bulk (-18°C to 3°C)
12 Months
Shelf Life, Cold, Part B Bulk (-18°C to 3°C)
12 Months
Electrical & Thermal Properties
Dielectric Strength, 25°C, Volts/mil
Volume Resistivity, 25°C, Ohm-cm x (10)12
Dielectric Constant, 25°C – 1 MHz
Dielectric Constant, 25°C – 1 kHz
Dielectric Constant, 25°C – 60 Hz
Dissipation Factor, 25°C – 1 MHz
Dissipation Factor, 25°C – 1 kHz
Dissipation Factor, 25°C – 60 Hz
Heat Capacity Cp, 25°C, J/g°K
Thermal Conductivity, 25°C, W/m°K
Coefficient of Thermal Expansion, ppm/°C
(-) 65°C to 75°C
75°C to 100°C
100°C to 150°C
Coefficient of Thermal Expansion, ppm/°F
(-) 85°F to 167°F
167°F to 212°F
212°F to 302°F
Click to View Chart
Hardness vs Temperature
(-75°C / -103°F)
87 A
(-25°C / -13°F)
50 A
5°C / 41°F
44 A
25°C / 77°F
37 A
50°C / 122°F
37 A
66°C / 150°F
37 A
80°C / 176°F
37 A
100°C / 212°F
37 A
120°C / 248°F
35 A
150°C / 302°F
35 A
Click to View Chart
Hardness vs Ambient Cure Time
1 Hour
4 A
2 Hours
6 A
4 Hours
11 A
8 Hours
14 A
12 Hours
14 A
1 Day
16 A
2 Days
19 A
3 Hours
22 A
4 Hours
23 A
1 Week
30 A
1 Month
41 A
Click to View Chart
Mechanical Properties
Tensile Strength per ASTM D638, 25°C, PSI
Elongation per ASTM D638, Type I, 0.125 in, 25°C
Tensile Lap Shear Strength - per ASTM D1002, 25°C, psi *
Aluminum Bare
470 Co
Steel Bare
260 Ad
Steel Ground
280 Ad
Primed Steel
150 Ad
Galvanized Steel
260 Ad
Tin Plated Steel
250 Co
Chrome Plated Steel
250 Co
Tensile Lap Shear Strength - per ASTM D3163, 25°C, psi **
FRP – Polyester Fiberglass
180 Ad
Garolite G-9 Melamine/Glass
130 Ad
Garolite G-10 Epoxy/Glass
130 Ad
Garolite XX Phenolic/Paper
190 Ad
Tensile Lap Shear Strength - per ASTM D3163, 25°C, psi **
110 Ad
120 Ad
PVC – Polyvinyl Chloride
150 Ad
CPVC – Chlorinated PVC
170 Ad
ABS – Acylonitrile Butadiene Styrene
120 Ad
PETG – Polyethylene Terephthalate
100 Ad
Lexan – Polycarbonate
90 Ad
Nylon 6/6 – Polyamide
160 Ad
40 Ad
Polyethylene LDPE
10 Ad
Polyethylene HDPE
40 Ad
Teflon PTFE – Polytetrafluoroethylene
20 Ad
Noryl – Polyphenylene Oxide/Polystyrene
170 Ad
Ultem Polyetherimide
100 Ad

Which Tough-Seal is Right for you?

Tough-Seal is a superior family of KEY sealants available in four standard formulations to fit a variety of potting applications. While all Tough-Seal formulations are durable hybrid epoxy elastomers that grip and protect under the most aggressive conditions, they are available in a combination of properties that vary in hardness, gel-time, working time, and flow.

Order Your Tough-Seal Evaluation Kit Today!

Your Evaluation Kit will include everything you need to perform your own high quality product evaluation for your application.

Ready To Talk to Us?

Tough-Seal is bulldog tough and bred to grip and protect, under the most aggressive conditions.

Contact us to discuss your specific application or requirements.