Engineering Tools & Calculators for Gaskets, Insulation & Thermal Materials

Formula: thermal resistance R = t / (k × A) (one-dimensional Fourier conduction), where t is bond-line thickness, k is thermal conductivity, and A is contact area. Temperature rise ΔT = Q × R, where Q is the heat conducted through the pad. Pad conductivity is measured per ASTM D5470.

Worked example: t = 1.0 mm (0.001 m), k = 3.0 W/m·K, A = 25 mm² (25×10⁻⁶ m²), Q = 5 W. R = 0.001 / (3.0 × 25×10⁻⁶) = 13.3 °C/W; ΔT = 5 × 13.3 = 66.7 °C. A softer, higher-k pad or larger area lowers both.

Conductivity ranges per H-O material catalog; use the exact value from your material data sheet.

Logic: SE is measured per MIL-DTL-83528 and enclosure effectiveness per IEEE Std 299; it is not computed here from a formula. Enter a target SE and the tool lists families whose third-party-tested SE meets or exceeds it. Standards apply at the assembled-enclosure level; the gasket is one of several variables.

Worked example: target 100 dB across 30 MHz–1 GHz → nickel-graphite silicone (SSP502, MIL-DTL-83528 Type M) typically exceeds 100 dB and qualifies as the cost-conscious baseline; the silver-filled Type B grade exceeds 110 dB and also qualifies for higher-criticality use.

Logic: nickel-graphite (Type M) is the cost-conscious baseline for most indoor cabinets; silver-filled grades (Types A/B/C) are specified where the SE target or bulk conductivity is higher; a soft conductive silicone sponge suits low-closure-force or irregular surfaces; and a UL 94 V-0 grade is specified where the enclosure is flame-rated.

Worked example: UHF (0.3–3 GHz) · door perimeter · indoor · no flame rating → nickel-graphite silicone (SSP502, Type M). Add a UL 94 V-0 requirement → the V-0 nickel-graphite grade.

Formulas: Compression % = (t_free − t_compressed) / t_free × 100. Inverted for sizing: required free thickness = closed gap / (1 − target compression / 100), then rounded up to the next standard sheet thickness. The closure force at the resulting percentage is read from the material’s compression-force-deflection curve, measured per ASTM D1056 or ASTM D3574 for cellular materials and ASTM D575 for solid rubber.

Worked example: a 0.085″ closed gap at a 30% target → required free thickness 0.121″ → next standard sheet 1/8″ (0.125″) → actual compression (0.125 − 0.085) / 0.125 = 32%, inside a typical closed-cell sponge band.

Logic: enter the minimum and maximum recommended compression for your material (from the data sheet) and your actual compression from the calculator above. A result inside the band is a reliable seal; below it risks leakage; above it risks compression set, governed by ASTM D395 (compression set) and ASTM D1056 (cellular compression). The bounds are material-specific, so they come from the data sheet, not from this page.

Worked example: a data sheet recommends sealing at 20–50% compression; your stackup gives 35% → inside the window, a reliable seal with margin on both sides.

Logic: hydrocarbon fuel or oil contact points to fluorosilicone foam; outdoor ultraviolet and ozone exposure points to EPDM closed-cell; low closure force or sound damping points to polyurethane open-cell; general sealing with some oil points to neoprene closed-cell; high temperature or a flame rating points to silicone foam (UL 94 grades). These mappings follow H-O’s material catalog guidance.

Worked example: outdoor · ultraviolet exposure · moderate temperature · low closure force → EPDM closed-cell. Change the media to fuel contact → fluorosilicone foam.

Logic: high heat or a flame rating points to silicone foam (BISCO®, available in UL 94 HB and V-0 grades); outdoor ultraviolet and ozone points to EPDM closed-cell; hydrocarbon fuel or oil points to fluorosilicone foam; general sealing with oil points to neoprene closed-cell; low-force or sound-damping points to polyurethane open-cell. These are qualitative family matches, not temperature ratings.

Worked example: high heat with a flame requirement → BISCO® HT-820 silicone foam (closed-cell, UL 94 V-0). Confirm the continuous-service temperature against the data sheet.

Formula: withstand voltage V = dielectric strength × thickness; safety margin = V_withstand / V_applied. Dielectric strength is measured per ASTM D149 (or IEC 60243) and is thickness-dependent, so it is read from the material data sheet at the relevant thickness, not assumed.

Worked example: using a data-sheet dielectric strength of 200 kV/mm (example value; use your material’s data sheet) and a thickness of 0.05 mm → V_withstand = 200 × 0.05 = 10 kV. Against an applied 2 kV → margin = 10 / 2 = 5×.

Formula: parts across = floor((W_sheet + g) / (W_part + g)); parts down = floor((L_sheet + g) / (L_part + g)); total = across × down; utilization % = (total × W_part × L_part) / (W_sheet × L_sheet) × 100, where g is the web/gutter spacing between parts. Pure geometry, so no material properties are involved.

Worked example: a 12″×12″ sheet, a 2″×3″ part, 0.1″ gutter → across = floor(12.1/2.1) = 5, down = floor(12.1/3.1) = 3, total = 15 parts; utilization = (15×2×3)/(12×12)×100 = 62.5%.

Factors: 1 mil = 0.0254 mm; °F = °C × 9/5 + 32; 1 W/m·K = 6.9335 BTU·in/(hr·ft²·°F); 1 psi = 6.894757 kPa. Durometer: ASTM D2240 defines Shore OO (soft foams and gels), Shore A (rubber and soft elastomers), and Shore D (hard plastics); there is no exact conversion between the scales, so choose the scale that matches the material’s hardness range.

Worked example: 40 mils = 40 × 0.0254 = 1.016 mm; 25°C = 25 × 9/5 + 32 = 77°F.

Full scale comparison on the durometer scale chart page.