JC237 Boron-Silicone is a fire and heat resistant field-castable neutron shielding material.  It is silicone elastomer-based and has a high hydrogen content. 

At temperatures up to 400 °F (204.4 °C), it will retain almost 90% of its initial hydrogen for extended periods.  The hydrogen content of JC237 is 67% of that found in water and contains 1% boron for thermal neutron attenuation.

JC237 is available in a variety of shapes and sizes.  It has a hard rubber-like consistency that will minimize any impact due to secondary missile formation and is self-extinguishing.

  • A field-castable liquid (multi-part kit)
  • Available as custom-made pre-cast solid pieces
  • Contains 1% boron along with a high hydrogen content in a hard rubber-like elastomer
  • Fire and heat resistant
Composition Data Important Properties
Hydrogen atom density / cm3: 4.49 x 10²²
Hydrogen weight percent: 4.74%
Boron atom density / cm3: 1.04 x 10²¹
Boron weight percent 1.17%
Total Density: 1.59 g/cm³ (99 lbs./ft³)
Radiation Properties
Macroscopic thermal neutron cross section: 0.80 cm⁻¹
Gamma resistance: 1 x 10¹⁰ rad
Neutron resistance: 5 x 10¹⁸ n/cm²
Physical Properties
State: Liquid/powder mix or pre-cast solid
Colour: Dark grey when cast
Odour: No significant odour
Machinability: Fair
Hardness: Shore “A” Durometer Scale = 66
Tensile Strength (ASTM D368): 50 psi (35,155 kg/ m²)
Compressive Strength: 450 psi (316,395 kg/ m²)
Thermal Properties
Recommended Temperature Limit: 204.4°C (400°F)
Heat Capacity: 0.4 cal/g °C
Specific Heat: 950 J/(Kg-K)
Thermal Conductivity: 0.584 W/(m-K)
Cubical Coefficient of Expansion: 3 x 10⁻⁴ in³/in³ °F (5.4 x 10⁻⁴ cm³/cm³ °C)
Linear Coefficient of Expansion: 1 x 10⁻⁴ in/in °F (1.7 x 10⁻⁴ cm/cm °C)
Vapor Pressure (mm Hg): 5
Evaporation Rate (ether=1): <1
Chemical Properties
Chemical Name & Synonyms: Borated Silicone
Trade Name & Synonyms: JC237
Chemical Family: Silicone Monomer
Formula: Silicone plus B and H compounds
Solubility in Water: <1%
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