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ROHACELLÆ 31 Polymethacrylimide (PMI) Rigid Foam Sheet

Subcategory: Composite Core Material; Polymer; Polymethacrylimide; Thermoset

Material Notes:
ROHACELL 31 is the lowest density grade and a very high strength:weight ratio.

General ROHACELL Information: ROHACELL is a closed-cell rigid expanded plastic material for lightweight sandwich construction. It has excellent mechanical properties, high dimensional stability under heat, solvent resistance and, particularly at low temperature, a low thermal conductivity. The strength and moduli values are the highest are the highest for any foamed plastic in its density range. ROHACELL is manufactured by hot forming of methacrylic acid/methacrylonitrile copolymer sheets. During foaming this copolymer is converted to polymethacrylimide.

Information supplied by Emkay Plastics, Ltd.

Physical Properties Metric English Comments
Density 0.032 g/cc 0.00116 lb/in„  ASTM D 1622-63
Water Absorption 19.5 % 19.5 %  Equilibrium at 98% RH
Moisture Absorption at Equilibrium 1.5 % 1.5 %  15% RH
Moisture Absorption at Equilibrium 2.9 % 2.9 %  30% RH
Moisture Absorption at Equilibrium 4.7 % 4.7 %  50% RH
Moisture Absorption at Equilibrium 6 % 6 %  65% RH
Water Absorption at Saturation 13 % 13 %  50 days immersion at 20ƒC.
Moisture Expansion Max 1 % Max 1 %  50 days immersion at 20ƒC.

Mechanical Properties
Tensile Strength, Ultimate 0.979 MPa 142 psi  ASTM D 638-68
Elongation @ break 3.5 % 3.5 %  ASTM D 638-68
Modulus of Elasticity 0.0353 GPa 5.12 ksi  ASTM D 638-68
Flexural Yield Strength 0.786 MPa 114 psi  ASTM D 790-66
Compressive Yield Strength 0.393 MPa 57 psi  ASTM D 1621-64
Shear Modulus 0.0128 GPa 1.85 ksi  ASTM C 273-61
Shear Strength 0.393 MPa 57 psi  ASTM C 273-61

Electrical Properties
Dielectric Constant 1.05 1.05  5.0 GHz
Dielectric Constant 1.05 1.05  10.0 GHz
Dielectric Constant 1.06 1.06  26.0 GHz
Dielectric Constant 1.08 1.08  2.0 GHz
Dissipation Factor 0.0001 0.0001  2.0 GHz
Dissipation Factor 0.0004 0.0004  5.0 GHz
Dissipation Factor 0.0008 0.0008  10.0 GHz
Dissipation Factor 0.0034 0.0034  26.0 GHz
Surface Resistance 2E+13 ohm 2E+13 ohm  

Thermal Properties
CTE, linear -100ƒC 25 µm/m-ƒC 13.9 µin/in-ƒF  
CTE, linear 20ƒC 37 µm/m-ƒC 20.6 µin/in-ƒF  ASTM D 696-70
Thermal Conductivity 0.031 W/m-K 0.215 BTU-in/hr-ft¾-ƒF  ASTM C 177-63
Maximum Service Temperature, Air 180 ƒC 356 ƒF  Dimensional stability per DIN 53424
Oxygen Index 19 - 20 % 19 - 20 %  

Descriptive Properties
Color White