COOLTHERM UR388

Harmonization Code : 3910.00.00.90 | Silicones in Primary Forms; Others

COOLTHERM UR388

Main features

  • 0.7 W/(m K) Thermal Encapsulation
  • 6,000 cP Mixed Viscosity
  • 0.32% TML and 0.02% CVCM

Product Description

CoolTherm® UR-388 FST Flame Retardant Urethane Encapsulant is a two-component urethane system for encapsulating and casting applications. It cures at room temperature to form a flame-retardant, semi-flexible material with typical thermal conductivity of 0.7 W/m·K and an operating-temperature range of -55°C to +130°C. The mixed system has a typical viscosity of 6,000 cP at 25°C and combines low cure exotherm with documented thermal-shock resistance and low-outgassing performance in high-vacuum test conditions. :contentReference[oaicite:0]{index=0}

Key features

  • Thermally conductive encapsulation: Provides typical cured thermal conductivity of 0.7 W/m·K.
  • Low-outgassing performance: Records 0.32% total mass loss and 0.02% collected volatile condensable materials under ASTM E595-77.
  • Room-temperature cure: Initially cures in less than 30 minutes at 25°C and may be mildly heat-cured at 60°C to accelerate cure.

Applications / Suitable for

  • Encapsulating applications
  • Casting applications
Product Family

COOLTHERM UR388

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TDS, SDS & Technical Documents

Technical Specifications

General Properties
Appearance
Appearance at room temperature.
Resin: Black Liquid | Hardener: Amber Liquid | Mixed: Black Liquid
Specific Gravity
Specific gravity (SG) is the ratio of the density of a substance to the density of a reference substance; equivalently, it is the ratio of the mass of a substance to the mass of a reference substance for the same given volume. For liquids, the reference substance is almost always water (1), while for gases, it is air (1.18) at room temperature. Specific gravity is unitless.
Resin: 1.53 | Hardener: 1.24 |
Physical Properties
Viscosity (Part A)
(Resin) 15000 mPa.s
Viscosity (Part B)
(Hardener) 70 mPa.s
Thermal Properties
Thermal Conductivity
Thermal conductivity describes the ability of a material to conduct heat. It is required by power packages in order to dissipate heat and maintain stable electrical performance. Thermal conductivity units are [W/(m K)] in the SI system and [Btu/(hr ft °F)] in the Imperial system.
0.7 W/m.K
Mechanical Properties
Elongation
Elongation is the process of lengthening something. It is a percentage that measures the initial, unstressed, length compared to the length of the material right before it breaks. It is commonly referred to as Ultimate Elongation or Tensile Elongation at break.
at break 50 %
Electrical Properties
Dielectric Strength
Dielectric strength is measured in kV per mm and is calculated by the Breakdown voltage divided by the thickness of the tested material. Those two properties go hand in hand and while Breakdown voltage is always thickness dependent, dielectric strength is a general material property. As an example, the dielectric strength of Polyimide is 236 kV/mm. If we place 1mm of Polyimide between two electrodes, it will act as an insulator until the voltage between the electrodes reaches 236 kV. At this point it will start acting as a good conductor, causing sparks, potential punctures and current flow.
15 kV/mm
Volume Resistivity
Volume resistivity, also called volume resistance, bulk resistance or bulk resistivity is a thickness dependent measurement of the resistivity of a material perpendicular to the plane of the surface.
7 x 10^15 Ohms⋅cm

Additional Information

Technical properties

As-supplied / before-processing properties

Typical properties of CoolTherm UR-388 FST resin, UR-388 hardener and the mixed encapsulant before cure. Values are not intended for specification purposes. :contentReference[oaicite:1]{index=1}

Property Value Unit Method / condition
Appearance Black liquid / Amber liquid / Black liquid — UR-388 FST resin / UR-388 hardener / mixed system
Viscosity 15,000 / 70 / 6,000 cP Resin / hardener / mixed system at 25°C; test method not stated
Specific gravity 1.53 / 1.24 / 1.50 — Resin / hardener / mixed system; test conditions not stated
Mix ratio 100:20 / 100:24 Resin:hardener By weight / by volume
Gel time 5 minutes Mixed system at 25°C; test method not stated
Suggested cure schedule 24 hours to 7 days — At 25°C; initial cure occurs in less than 30 minutes
Shelf life 6 months Each component from date of manufacture when stored at 25°C in the original, unopened container
Technical properties

After-processing / final-state properties

Typical cured properties of CoolTherm UR-388 FST. The source does not identify the cure schedule used to prepare the cured-property specimens. Values are not intended for specification purposes. :contentReference[oaicite:2]{index=2}

Property Value Unit Method / condition
Thermal conductivity 0.7 W/m·K Test method, temperature and specimen thickness not stated
Operating-temperature range -55 to +130 °C Documented range for parts and devices; retained-property data are not stated
Hardness 88 Shore A ASTM D2240
Tensile strength 15.58 (2,260) MPa (psi) ASTM D638
Elongation at break 50 % ASTM D638
Volume resistivity 7 × 1015 ohm-cm At 25°C; ASTM D257
Dielectric constant 6.2 — At 25°C and 1 MHz; ASTM D150
Dissipation factor 0.013 — At 25°C and 1 MHz; ASTM D150
Total mass loss 0.32 % ASTM E595-77
Collected volatile condensable materials 0.02 % ASTM E595-77

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