Kaxite Sealing manufactures PTFE envelope gaskets — a chemically inert ePTFE envelope wrapped around a resilient CNAF, graphite or ceramic core. The combination delivers PTFE's full pH 0–14 chemical resistance with far lower creep, better low-bolt-load sealing and superior tolerance for rough, pitted and irregular flange faces. We die-cut, CNC-machine and hand-fabricate to ANSI B16.21, ASME B16.20, DIN, JIS and custom drawings. Procurement teams choose us for factory-direct bulk pricing, documented traceability and 7–15 day lead times.
Our proprietary envelope construction creates uniform thickness with no folded seams or weak points — the most common cause of premature PTFE envelope failure. Only the smooth ePTFE film touches the process media.
Send us your media, temperature and flange class. We match CNAF for general chemical service at moderate temperature, graphite for high-temperature and thermal cycling, or ceramic fibre for extreme thermal duty. No guessing.
Solid PTFE gaskets cold-flow and leak. The compressible core of an envelope gasket takes up bolt load and recovers, so joints stay tight through thermal cycling and vibration. Compression set is below 15%.
Resin, expansion, core lamination, die-cutting and CNC machining all run inside our Ningbo plant. No trading layer, so your PTFE envelope gasket price stays stable even on repeat bulk orders.
A composite sealing element: a soft compressible CNAF, graphite or ceramic core fully encased in a seamless expanded PTFE envelope. The envelope provides full pH 0–14 chemical resistance, non-stick release and a wide thermal window; the core provides compression, recovery and low bolt-load sealing. Available as die-cut gaskets to ANSI B16.21 / ASME B16.20 / DIN / JIS flanges, and as custom square, rectangular, oval or irregular shapes for reactors, manways and proprietary equipment. FDA and USP Class VI grades available on request.
| Component | Material Options | Key Characteristics |
|---|---|---|
| Envelope (outer shell) | Expanded PTFE (ePTFE) | Chemically inert across pH 0–14, wide temperature range, non-stick, low creep |
| Core filler | Compressed Non-Asbestos Fibre (CNAF) | Good general chemical resistance, resilient, cost-effective for moderate duty |
| Core filler | Exfoliated graphite | Superior thermal conductivity, ideal for high-temperature and thermal cycling |
| Core filler | Ceramic fibre | Extreme temperature resistance for aggressive thermal applications |
| Parameter | Typical Range / Value | Notes |
|---|---|---|
| Service Temperature | -73 to +260 °C | Short peaks to +288 °C depending on filler — consult for specific duty |
| Pressure Range | Up to 103 bar | Depends on flange design, gasket dimensions and filler |
| pH Range | 0 – 14 | Full acid-to-alkali inertness from the PTFE envelope |
| Compression Set | < 15 % | Maintains sealing force under sustained bolt load |
| Applicable Standards | ANSI B16.21, ASME B16.20, DIN, JIS | Standard and custom sizes to global flange standards |
| Flange Class | Nominal Pipe Size (NPS) | Standard Thickness |
|---|---|---|
| 150# | 1/2" to 24" | 1/16", 1/8" |
| 300# | 1/2" to 24" | 1/8", 1/4" |
| 600# | 1/2" to 24" | 1/8", 1/4" |
| 900# & 1500# | 1/2" to 12" | 1/4" |
Flange standard, ID/OD, thickness, media, temperature, pressure and quantity.
We match envelope material and core filler to your service — CNAF, graphite or ceramic.
Unit price, MOQ, tooling cost if applicable, lead time and trade terms in 24 hours.
Free cut samples of standard constructions for fit and material evaluation before bulk.
7–15 days for standard sizes; FOB / CIF / DDP with pre-shipment photos on bulk orders.
Solid PTFE gaskets are chemically resistant but prone to cold flow (creep) under load, which leads to sealing failure over time. A PTFE envelope gasket combines the chemical barrier of a PTFE skin with the compressibility and recovery of an inner filler. This design significantly reduces creep, seals at lower bolt loads, and is far more forgiving on rough, pitted or slightly damaged flange surfaces than solid PTFE.
Yes — with the right filler. Graphite-core envelope gaskets are excellent for steam applications because the graphite delivers exceptional thermal stability and recovery, while the PTFE envelope protects the core from oxidation at lower temperatures and contains graphite particles. Confirm the continuous operating temperature is within rated limits for your specific construction before ordering.
Use graphite filler for high-temperature service (consistently above 232 °C), thermal cycling duty, or where superior fire safety is required — graphite is non-combustible. Choose CNAF filler for general chemical service at moderate temperatures (typically up to 204 °C), for hydrocarbons and solvents, or where cost-effectiveness matters for less severe duty. Our engineers can confirm the optimal choice once you share process data.
Yes. The PTFE used in Kaxite envelopes is a high-purity polymer that meets relevant FDA regulations for food contact, and we can manufacture gaskets with fillers that are also certified for such applications. For critical pharmaceutical or bioprocessing requirements calling for USP Class VI certification, we offer specific product lines with full traceability and documentation.
Ensure flange faces are clean, undamaged and aligned. Install the gasket dry — do not apply adhesive or lubricant to the PTFE surface. Centre the gasket carefully on the flange, then torque the bolts using a calibrated wrench in a cross-pattern (star) sequence in incremental stages: 30%, 60%, and finally 100% of the target torque. Always follow the equipment or flange manufacturer's bolting procedure for final torque values.
Yes — custom fabrication is a core strength. We routinely produce envelope gaskets in square, rectangular, oval and other irregular shapes for reactors, manways, heat exchangers and proprietary machinery. Send us a drawing or a sample and we will return a gasket matching your exact dimensional and performance requirements.
PTFE has an unparalleled chemical resistance profile, but there are a few extreme substances that can attack it — molten alkali metals (sodium, potassium) and certain fluorine compounds at high temperature and pressure. For strong oxidisers such as chlorine or bromine, filler selection and operating parameters need special review. Always disclose the full chemical and physical conditions so we can complete a compatibility review and recommend the correct construction.
MOQ is negotiable for trial and prototype orders. Standard sizes ship in 7–15 days; custom shapes to drawing typically take 15–20 days. Trade terms include FOB Ningbo / Shanghai, CIF and DDP. Pre-shipment photo and video verification is provided on all bulk orders, along with inspection reports and material certificates.
Send us your flange standard (ANSI / DIN / JIS), ID and OD, thickness, gasket shape, media, operating temperature and pressure, filler preference or quantity. Our export team replies within 24 hours and confirms grade selection, lead time, packaging and documentation before you place a bulk order.
