BMI vs Cyanate Ester
Polymer · grade comparison
BMI and Cyanate Ester are both polymer grades. Cyanate Ester is the stronger of the two: tensile strength 80 MPa (11.6 ksi) against 72 MPa (10.4 ksi) for BMI, about 11% more. Cyanate Ester is the more ductile: elongation 2.6% versus 2% for BMI. Cyanate Ester is lighter (1.21 g/cm³ vs 1.3 g/cm³ for BMI) and BMI is stiffer (4 GPa vs 3.1 GPa).
BMIChoose it when the part sees heat.
Cyanate EsterChoose it when strength drives the design, or when the part is bent, formed or impact-loaded.
BMI vs Cyanate Ester: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all polymer grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all polymer grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Shear Modulus
Tensile Strength (Ultimate)
Elongation at Break
Compressive Strength
Compressive Modulus
Flexural Strength
Flexural Modulus
Izod Impact, Notched
Hardness, Rockwell M
Bulk Modulus
Hardness, Shore D
Same in both: Poisson's Ratio 0.35 · Shear Strength 55 MPa8 ksi · Fracture Toughness (K_IC) 0.6 MPa·√m0.55 ksi·√in
Physical
Density and transition temperatures.
Density
Glass Transition (Tg)
Water Absorption (24 h)
Water Absorption (Saturation)
Refractive Index
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Min Service Temperature
Heat Deflection Temp. @ 0.45 MPa
Heat Deflection Temp. @ 1.8 MPa
Limiting Oxygen Index
Same in both: Specific Heat Capacity 1,150 J/kg·K0.27 BTU/lb·°F · Max Service Temperature (short-term) 300°C572 °F
Electrical
Conductivity and insulation.
Electrical Resistivity
Dielectric Strength
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Volume Resistivity
Surface Resistivity
Same in both: Comparative Tracking Index (CTI) 200 V
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
UV / Weathering Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Polishability
Mold Shrinkage
Processing Melt Temperature (typ.)
Mold Temperature (typ.)
Same in both: Weldability 0 / 100 · Formability (cold) 5 / 100
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Same in both: Embodied Carbon (primary production) 9.5 kg CO₂/kg · Embodied Water 300 L/kg35.9 gal/lb · Typical Recycled Content 0%
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Thermal Diffusivity
Same in both: Thermal Shock Resistance Index 0
Strength versus weight
Yield strength against density for every polymer grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | BMI | Cyanate Ester |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$$$ High | $$$$ High |
| Min. machined wall | — | — |
| Best machined surface | — | — |
BMI vs Cyanate Ester — frequently asked
Is Cyanate Ester stronger than BMI?
Yes. Cyanate Ester has a typical tensile strength of 80 MPa (11.6 ksi) against 72 MPa (10.4 ksi) for BMI — about 11% more.
Which is cheaper, BMI or Cyanate Ester?
Both sit in the same relative cost tier ($$$$, high); the part price will be decided by machining time, tolerance and quantity rather than by the material.
Which is easier to machine, BMI or Cyanate Ester?
Cyanate Ester. Its machinability rates good (55/100) against fair (50/100) for BMI.
Ready to make it?
Upload a CAD file and FabDigit prices the part in BMI and Cyanate Ester side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.