For general fabrication, virgin PTFE is rarely the right call: unfilled resin has poor creep resistance, low wear life, and limited elastic recovery, so almost every loaded or dynamic part is built from a filled compound rather than neat resin [S2][S5].
The 2026 commercial landscape offers 620+ PTFE grades across virgin, glass, carbon, graphite, bronze, stainless steel, MoS2, polyimide, and mineral-filled families, with seal-grade filler loadings commonly at 15% or 25% glass, 40-60% bronze, and 20-35% carbon or graphite [S1][S6].
Virgin PTFE: What It Is Good For, and Where It Fails
Virgin (unfilled) PTFE retains the polymer's headline properties: an operating window of -200°C to +260°C, near-universal chemical resistance, an extremely low coefficient of friction, and excellent dielectric behaviour, which is why it dominates chemical linings, labware, and static insulators [S5].
It is mechanically weak: creep under sustained load, poor elastic recovery (no memory), and low wear resistance mean virgin PTFE is the wrong pick for dynamic seals, bearings, or any geometry that must hold a tight tolerance under pressure [S2][S5]. For those cases the same base resin is compounded with a filler that addresses the specific failure mode you are designing against.
Filler Matrix: How Each Common Filler Changes the Resin
Glass-filled PTFE (typically 5-60% glass, with 15% and 25% as the most common seal grades) reduces the coefficient of thermal expansion, lifts compressive strength, and cuts cold flow, making it the default for tight-tolerance bearings, seals, and dielectric structural parts [S2][S4][S6].
Carbon-filled PTFE (often 20-35%) adds thermal conductivity, electrical conductivity, and improved wear life, and is widely used where static dissipation or higher PV (pressure x velocity) ratings are required [S2][S4][S6]. Graphite-filled PTFE lowers friction further and is the go-to for self-lubricating bearings, seals, and piston rings; it is frequently combined with carbon or glass to capture the benefits of multiple fillers in one compound [S2][S4].
Bronze-filled PTFE (40-60% bronze) is the highest-density, highest-thermal-conductivity option, specified for high-load dynamic bearings and seal rings exposed to heat, while MoS2-filled PTFE is used as a dry-film lubricant in high-PV slide bearings, thrust washers, and mechanical seals, and is often blended with glass or bronze to balance properties [S2][S4][S6].
Stainless-steel-filled PTFE acquires the strength to take sustained mechanical load and tolerates high-temperature service, which is why it is specified for steam, hot-liquid, and food-and-drives mechanical components, with the trade-off that it is more abrasive on mating surfaces [S4]. Mineral-filled PTFE rounds out the set: it is the regulatory-friendly choice where FDA, EU 10/2011, or pharmaceutical contact is required, and is favoured over bronze or stainless when galvanic or contamination risk must be avoided [S2][S5].
Decision Table: Matching Filler to Service Condition
Use this four-row check before calling out a grade: if the service hits two or more "use X" columns, the blended grade (carbon+glass, graphite+bronze, MoS2+glass) is the engineering answer rather than a single-filler compound [S2][S4][S6].
Glass is correct for tight tolerance under load; carbon is correct for thermal conductivity plus static dissipation; graphite is correct for low-friction self-lubrication; bronze is correct for high-load heat-soaked dynamic duty; stainless is correct for steam and high-temp mechanical parts; MoS2 is correct for high-PV dry sliding; mineral is correct for regulatory/chemical purity; virgin is correct only for static, low-load, chemically aggressive service [S2][S4][S5][S6].
Fabrication Process Choices by Filler Family
Glass-filled PTFE, like most filled grades, is most commonly machined from compression-molded stock or sintered billets using sharp tooling at controlled cutting speeds, with inert-gas sintering an optional step to further reduce porosity and creep in glass compounds [S4][S7].
For filled grades, machinability differs in two practical ways: glass- and stainless-filled compounds are abrasive and shorten tool life faster than virgin resin, while carbon and graphite are less aggressive on cutting edges, so feeds, speeds, and tool material (carbide vs HSS) must be re-selected per filler rather than carried over from a virgin-PTFE setup [S4][S7]. Standard CNC milling and turning, compression molding for raw shapes, and ram extrusion for rod and tube remain the four process pillars across the 620+ commercial grades catalogued for 2026 [S1][S7].
Industry Selection Map and the Boundary With PEEK / PFA
By industry, PTFE is the default for chemical-processing linings, oil-and-gas static valve seats and gaskets, semiconductor seals and tubing, aerospace insulation, and FDA food/pharma gaskets, while PEEK is preferred for high-load dynamic seals, PFA for semiconductor structural purity, polyimide for load-bearing aerospace parts, and silicone for dynamic food/pharma sealing [S5].
That same matrix is why engineering plastics selection frames PTFE as the chemically dominant, mechanically weakest entry in the high-performance polymer set: when a part must take sustained load or dynamic contact, the engineering decision is which filled-PTFE compound (or which alternative polymer) absorbs the mechanical duty the base resin cannot.
Limitations, Failure Modes, and Standards to Watch
Three failure modes dominate PTFE service regardless of filler: creep under sustained load (mitigated by glass, bronze, or stainless fillers), cold flow above the crystalline melt point (~327°C), and abrasive wear on mating surfaces when glass- or stainless-filled grades run against soft counterfaces [S2][S4].
For regulatory use, FDA-grade gaskets and pharmaceutical-contact parts are typically specified as mineral-filled or specially certified virgin grades; always verify the compound carries the document set (FDA, EU 10/2011, USP Class VI where relevant) the end-user requires, and note that approvals live with the specific compound, not with the generic "PTFE" label [S2][S5].
Seal design pulls several of these threads together: for a deeper pass on geometry, lip style, and custom manufacture the PTFE seals type and design guide is the next node, while a sister application piece covers PTFE selection for rail industry: grades, fillers, and certification map where flame, smoke, and EN 45545 requirements change the filler call. Two trackable signals to watch: any 2026 release of additional low-creep modified PTFE resins for high-PV compressor duty, and a tightening of EU food-contact documentation on mineral-filled compounds.
Spec-level background on the components involved: pressure transmitter, and flow meter.