Most elastomeric gaskets top out between 200°F and 500°F, while metallic and semi-metallic constructions carry service temperatures from roughly 1,000°F to 2,000°F, and graphite climbs to 900°F in oxidizing atmospheres (up to 3,000°C in non-oxidizing service) [S3]. The selection question is rarely "which is hotter" but "what continuous temperature, pressure, and chemical environment the joint actually sees."
For a process engineer, the practical dividing line sits at about 350°F (177°C): above that threshold, an elastomer is no longer "ordinary" and the material menu shifts toward compressed non-asbestos, PTFE, graphite, spiral-wound, and solid metal gaskets [S1][S6]. This article lays out a spec-first comparison of elastomeric versus metallic gasket families on temperature, pressure, chemical compatibility, and mechanical behavior, then closes with a per-application recommendation. The selection logic mirrors the same constraint-driven approach used in EPDM third-monomer selection for elastomer chemistry, where the operating envelope dictates the polymer family before the part number is even discussed.
Elastomeric Gasket Temperature Envelopes by Polymer
General-purpose elastomers (NBR/SBR/Neoprene) cap near 200–250°F (93–121°C), and the "high-temperature" elastomer tier begins at roughly 225°F (107°C) for EPDM, climbs to 400–425°F (204–218°C) for standard silicone, reaches 500°F (260°C) for high-temperature silicone compounds, and stops at about 500°F (260°C) for Viton/FKM in continuous service [S2][S3][S4]. EPDM at -60°F to +250°F is the default outdoor choice; silicone at -80°F to +425°F (extendable to +600°F with high-temp compounds) covers ovens and food-grade lines; fluorosilicone at -103°F to +400–500°F adds jet-fuel resistance; Viton at 0°F to +400°F handles aggressive solvents and hydrocarbons [S4].
The hard rule engineers cite: an operating temperature above 350°F (177°C) is already "high temperature" for any polymer, and above 500°F (260°C) the flexibility of rubber is lost, so the joint cannot be classified as elastomeric anymore [S1][S9]. Heat aging tests in standards such as ASTM D 573, ASTM D 1056, UL 50, UL 48, UL 508, and UL 157 expose gaskets for 70–168 hours at 158–212°F (70–100°C) before measuring tensile, elongation, or compression deflection, which is how manufacturers qualify these polymer envelopes [S1].
Compressed Non-Asbestos and PTFE: The Semi-Elastomer Middle
Compressed non-asbestos (CNAF) sheets, made from aramid fibers in an NBR or SBR binder, span -100°F to 750°F (-73°C to 399°C) and dominate pipelines, refineries, and chemical processing where steam and mild chemicals are present [S3]. Most CNAF grades tolerate up to 700–750°F in continuous service, which is roughly 250°F higher than the best elastomer and bridges the gap before graphite and metallic constructions take over [S2][S7].
PTFE stops at 500°F (260°C) continuous, well below CNAF, but its chemical inertness makes it the default for aggressive acids, bases, and solvents in pharmaceutical and food service, where temperature is the trade-off the specifier accepts [S2][S3]. Vermiculite-filled spiral-wound gaskets, the next step up, carry an upper limit near 1,800°F (982°C) and are the most common choice for sustained service above 750°F in pipe joints [S2]. For a deeper look at the materials side, the reference page on gasket material classes summarises the same polymer-to-fabric-to-metal hierarchy used in most supplier catalogs.
Metallic and Semi-Metallic Gaskets: 1,000°F and Beyond
Solid metal gaskets (stainless steel, Inconel, soft iron, Monel) routinely reach 1,000°C and above depending on alloy grade, and that is the floor rather than the ceiling for metallic sealing [S10]. Spiral-wound gaskets with stainless steel windings and graphite or PTFE fillers span -320°F to 2,000°F (-196°C to 1,093°C), with the filler usually setting the practical ceiling rather than the metal itself [S3]. Ring-type joints (RTJ) made from soft iron or stainless steel cover -450°F to 1,300°F (-268°C to 704°C) and are standard for high-pressure oil and gas flanges [S3].
Metal-jacketed gaskets with a stainless or copper core and a soft graphite or ceramic filler run from -400°F to 1,600°F (-240°C to 870°C), which is the typical heat-exchanger and boiler envelope [S3]. Kammprofile gaskets, a metal core with graphite or PTFE facings, span -328°F to 1,800°F (-200°C to 982°C) and are specified for heat exchangers, compressors, and reactors where seal integrity matters more than cost [S3]. For ultra-high service, ceramic gaskets go to 2,300°F (1,260°C) for kilns and furnaces, and mica-based gaskets reach 1,832°F (1,000°C) in exhaust and turbine service [S3].
Criteria-Based Comparison: Elastomer vs Metallic Family
Lining the families up against four decision criteria (continuous temperature, pressure class, chemical compatibility, compressibility/conformability) gives a clean read for spec writing. Elastomers win on compressibility and cost but lose above 400–500°F and on aggressive chemicals; CNAF/PTFE give a chemical step-up with a 500–750°F ceiling; semi-metallics (graphite, spiral-wound, kammprofile) carry 1,000–2,000°F service at the cost of higher seating stress; solid metals take over above ~1,000°C and in fire-safe or high-pressure API flanges. [S3]
The table below condenses the same numbers used throughout supplier catalogs. Continuous service temperature is the primary filter; pressure rating and chemical resistance are the secondary filters. Cost and ease of installation are not listed because the spread is wide within each family, but as a rule the column moves left-to-right roughly in step with seating stress and flange class.
Vacuum, Permeation, and Outgassing Trade-Off
In general, elastomer gaskets add gas loads to a sealed system from outgassing and permeation, while metal gaskets do not. For a hydrocarbon or refrigerant line, the elastomer's permeability is rarely the binding constraint; for a semiconductor vacuum chamber or a cryogenic feed line, the same elastomer becomes a contamination source and is rejected even at modest temperatures. This is one of the few cases where temperature is not the deciding variable at all.
Cryogenic service reinforces the point: spiral-wound and RTJ gaskets remain the default below -100°F because elastomers lose flexibility and CNAF binders crack long before the temperature limit shown on the catalog is reached [S3]. When the operating envelope crosses both 500°F and a hard vacuum, the shortlist collapses to graphite-filled spiral-wound, kammprofile, or solid metal, with the filler chosen for the chemistry of the process fluid rather than the temperature alone.
Application-Specific Recommendations
For HVAC, water, and steam at 250°F and below, EPDM or NBR is the right call: cheap, compressible, and qualified to UL 50 / UL 157 heat aging after 70–168 hours at 158–212°F [S1][S3]. For oven, food-grade, or pharmaceutical service up to 425°F, silicone (extendable to 600°F with high-temp compounds) is the default, with PTFE as the chemical-resistance variant up to 500°F [S3][S4]. For steam headers and refinery pipe flanges in the 500–750°F band, CNAF is the workhorse; vermiculite- or graphite-filled spiral-wound gaskets take over above 750°F [S2][S3].
For API 6D high-pressure oil and gas flanges, RTJ soft-iron or stainless gaskets are standard practice regardless of operating temperature, and the question reduces to which alloy class (soft iron, low-carbon steel, 304/316 stainless, Monel) is rated for the process fluid and H2S service. For heat exchangers, autoclaves, and boiler penetrations, metal-jacketed or kammprofile gaskets carry the 1,000–1,800°F envelope that elastomers physically cannot reach [S3]. The same constraint-driven logic that drives non-contact temperature measurement choices applies here: the joint's true operating envelope, not the catalog headline, decides the material.
Trackable signals for the next quarter: revised CNAF formulations for 800°F+ service, ongoing migration from compressed asbestos to aramid binders, and tighter ASTM D 573 heat-aging data being published for high-temperature silicone compounds. Watch the IGP, Hennig, and Monroe material guides for new upper-temperature claims on CNAF and on graphite-filled kammprofile gaskets, as these are where the 2026 spec updates tend to land first [S3][S7][S10].
Detailed specification references: temperature controller, and temperature measurement.