PTFE sheet, rod and tube are all made from the same polymer, yet a buyer comparing quotations will often find a wide spread in price for what appears to be the same material. The difference usually comes down to the process behind it. PTFE can be shaped by three main routes — compression molding, skiving and ram extrusion — and each one produces different void content, thickness tolerance and size limits. Knowing which route suits which part is the difference between a quotation you can compare and one you cannot.

Why PTFE Cannot Be Melt Processed

Unlike POM or Nylon, PTFE cannot be injection molded or melt extruded. Its melt viscosity is high enough that the material will not flow, which is why the industry works around it with powder-based processes. The first melting point of virgin PTFE is about 342 °C, falling to roughly 327 °C once the resin has been sintered, and rapid thermal degradation begins above about 410 °C. Those three figures set the working window for every process described below.

Compression Molding

Compression molding is the route to thick plate and block. Granular PTFE powder is compacted at room temperature into a self-supporting preform, at pressures spanning roughly 10–100 MPa; free-flow granular grades are typically recommended in the 25–35 MPa band. The preform is then free-sintered in an oven at 360–380 °C, above the resin's melting point, followed by a controlled cooling cycle that sets the crystallinity. Molded plate is commonly supplied from about 2 mm up to 100 mm thick, at 1,200 × 1,200 mm and beyond, and it carries the lowest void content of the three routes — unfilled PTFE density sits at 2.14–2.20 g/cm³.

Skiving

Skiving produces thin sheet by cutting rather than forming. A sintered cylinder — most often made by compression molding or isostatic molding — is mounted on a lathe, and a blade peels a continuous sheet off its surface, the same principle as cutting a veneer. Gauges from about 0.03 mm to 4 mm are produced this way, in widths up to around 1,200 mm. The sheet inherits the density of the billet it was cut from, and the peeling action orients the polymer near the cut surface — which is why the process belongs on the drawing rather than being left to the supplier to decide.

Ram Extrusion

Ram extrusion combines compaction and sintering in a single pass. Powder is charged into a heated die tube and pushed through by a reciprocating ram, producing continuous rod from roughly 4 mm to 150 mm in diameter, and tube, with no joint anywhere along the length. Because the material sinters as it moves, output length is limited by handling rather than by press or furnace size. Density is good, though generally slightly below that of a well-controlled molded billet.

How to Choose the Right Process

The choice usually follows from what governs the part. Chemical equipment lining and large backing plates call for molded plate, because they need thickness and a single piece with no joint. Gaskets, diaphragms and thin electrical insulation call for skived sheet, because they need uniform thin gauge. Valve seats, bearings and wear parts are normally molded or skived and then machined to tolerance, while rod for machining and tube for fluid handling come from ram extrusion. Thickness drives cost more than resin price does: molding a thin sheet wastes both material and furnace time, whereas skiving turns one thick billet into many thin sheets. Sizes beyond the standard range — 1,500 × 1,500 mm, for example — are worth confirming with the manufacturer rather than assuming they are held in stock.

Summary

All three routes deliver the same polymer, and none of them is superior in the abstract. What differs is void content, which governs electrical insulation, sealing behaviour and chemical duty; thickness tolerance; and the size limits each process can reach. A specification that names only the material grade leaves the supplier to choose the process, and that choice is what the quotation ultimately reflects. Naming the process — or asking which one a supplier intends to use — is what makes quotations comparable.

About SHINGPLAST

Shandong Seon New Material Technology Co.,Ltd specialises in fluorine materials and related engineering plastics from our base in Zibo, Shandong. Our range covers PTFE sheet, plate, rod and tube , other engineering plastics and raw materials ， and custom CNC machined parts . These materials are chosen for corrosion resistance, low friction, high and low temperature performance, electrical insulation and non-stick behaviour. Most of our products hold international approvals such as ISO, FDA, CE, SGS, RoHS and REACH, and we serve customers in more than 100 countries across Europe, Southeast Asia and the Middle East. For material selection advice or a quotation, write to info@seontec.com, call +86 185 6180 6005, or message us on WhatsApp at +86 185 6180 6005.