What Determines the Wear Resistance of Modified PTFE Sheets?
2026-10-30
A maintenance engineer replaces a PTFE guide pad on a packaging machine every eight weeks. The pad is made from pure PTFE. It has a low friction coefficient, but it wears into a groove and the machine loses alignment. The engineer switches to a Modified PTFE Sheets grade with 15 percent glass fiber and 5 percent graphite. The new pad lasts eleven months. The friction coefficient is slightly higher, but the wear rate is much lower. The engineer wants to understand what controls the wear rate and how to specify the right grade for the next machine. This guide explains the three factors that determine the wear resistance of a modified PTFE sheet.
1. Why Does Unmodified PTFE Wear Out So Fast Under Sliding Contact?
Pure PTFE has a very low friction coefficient, around 0.04 to 0.10, which is why it is used for non-stick and low-friction applications. But pure PTFE has a low load-bearing capacity. Under a sliding contact, the surface layer shears and is transferred to the counterface in thin flakes. The wear rate is high, especially when the product of the contact pressure and the sliding velocity, known as the PV value, exceeds the material limit. Pure PTFE also creeps under load, so the pad deforms and the contact pressure becomes uneven. In our factory, we produce Modified PTFE Sheets for sealing, guiding, and sliding applications. Ningbo Taifno PTFE Plastic Products Co., Ltd. has been manufacturing PTFE products for over 12 years.
The modification does not change the low friction advantage. It changes the load-bearing capacity and the wear mechanism. The fillers carry part of the load and reduce the shear of the PTFE matrix.
2. What Does the Filler Actually Do Inside the PTFE Matrix?
The filler performs three functions. The first is load support. The filler particles are harder than the PTFE and carry part of the contact load, which reduces the stress on the PTFE matrix. The second is thermal conductivity. PTFE is a poor conductor of heat, and the friction heat builds up at the contact. The filler conducts the heat away and reduces the surface temperature. The third is the interruption of the wear debris film. The filler particles break the continuous transfer film that pure PTFE forms on the counterface, and the broken film is less effective at lubricating the contact. The table below compares the common filler systems.
| Filler system | Friction coefficient | Wear rate (relative) | Temperature limit | Chemical resistance |
| Glass fiber (15 – 25%) | 0.10 – 0.15 | 0.3 | 260°C | Good (not for HF, hot alkali) |
| Carbon fiber (10 – 20%) | 0.12 – 0.18 | 0.2 | 280°C | Good |
| Graphite (5 – 15%) | 0.08 – 0.12 | 0.4 | 300°C | Good |
| Bronze (40 – 60%) | 0.15 – 0.20 | 0.15 | 250°C | Poor (not for acids) |
| Polyimide (10 – 20%) | 0.15 – 0.25 | 0.25 | 300°C | Good |
In our factory, we select the filler system based on the application. For a guide pad in a packaging machine, the glass fiber and graphite combination provides a good balance of wear resistance and low friction. For a seal in a chemical pump, the carbon fiber grade provides better chemical resistance. Ningbo Taifno PTFE Plastic Products Co., Ltd. provides the filler composition and the wear test data with each grade.
3. How Does Filler Content and Dispersion Determine Wear Rate?
The filler content has an optimum. If the content is too low, the filler does not form a continuous load-bearing network, and the wear rate remains close to that of pure PTFE. If the content is too high, the material becomes brittle, and the filler particles abrade the counterface. The optimum content depends on the filler type. For glass fiber, the optimum is around 15 to 25 percent. For carbon fiber, the optimum is around 10 to 20 percent. For bronze, the optimum is around 40 to 60 percent. The dispersion also matters. If the filler particles agglomerate, the local wear rate increases and the surface becomes rough. The table below shows the effect of filler content on wear rate and mechanical properties for a glass fiber grade.
| Glass fiber content | Wear rate (relative) | Tensile strength (MPa) | Elongation at break |
| 0% (pure PTFE) | 1.0 | 25 | 300% |
| 10% | 0.55 | 22 | 220% |
| 15% | 0.35 | 20 | 180% |
| 20% | 0.30 | 18 | 150% |
| 25% | 0.32 | 16 | 120% |
| 30% | 0.45 | 14 | 80% |
Materials engineer's note: The wear rate reaches a minimum at around 20 percent glass fiber and then increases as the content rises further. The increase is caused by the brittleness of the matrix and by the abrasive action of the glass fiber on the counterface. In our factory, we compound the filler into the PTFE using a high-shear mixing process and verify the dispersion with a microscope. A poor dispersion shows as clusters of filler, and the wear rate of that batch is higher than the specification. Ningbo Taifno PTFE Plastic Products Co., Ltd. checks the dispersion of every batch before pressing.
4. Why Do Compaction and Sintering Parameters Decide the Real Wear Performance?
The wear resistance is not determined by the formulation alone. The compaction and sintering process determines the porosity and the crystallinity, and both affect the wear rate. A low compaction pressure leaves voids in the sheet, and the voids act as stress concentrators that initiate cracks during sliding. A high compaction pressure reduces the voids but can cause internal stresses if the pressure is not released slowly. The sintering temperature and time determine the degree of crystallinity. A high crystallinity increases the hardness and the wear resistance, but it also increases the brittleness. In our factory, we control the compaction pressure at 30 to 50 MPa and the sintering temperature at 360 to 380°C. We measure the density and the crystallinity of every batch and provide the data with the shipment. Ningbo Taifno PTFE Plastic Products Co., Ltd. also performs a wear test on a sample from each batch.
We recommend that the buyer verify the density of the sheet before machining. A density below 2.10 grams per cubic centimeter for a glass-filled grade indicates incomplete sintering or excessive porosity, and the wear rate will be higher than expected.
5. How Should Engineers Specify and Verify Modified PTFE Sheets for Wear Applications?
The specification should include five items. The first is the filler system and the filler content. The second is the density and the crystallinity. The third is the tensile strength and the elongation at break. The fourth is the wear rate test method and the acceptance limit. The fifth is the operating PV value and the counterface material. The verification should include three tests. The first is the density and crystallinity measurement. The second is the tensile test. The third is the wear test, preferably on a pin-on-disk or a block-on-ring machine. In our factory, we perform these tests on every batch and provide the test report with the shipment. Ningbo Taifno PTFE Plastic Products Co., Ltd. also offers application support to help the engineer select the filler system and the PV limit.
We recommend that the designer consider the counterface material. A glass-filled PTFE is abrasive to soft counterfaces such as aluminum. For an aluminum counterface, a carbon fiber or graphite grade is a better choice because it is less abrasive and it forms a transfer film that protects the aluminum.
Frequently Asked Questions About Modified PTFE Sheets and Wear Resistance
Summary for Materials Engineers and Designers
The wear resistance of Modified PTFE Sheets is determined by three factors: the filler system, the filler content and dispersion, and the compaction and sintering process. The filler system determines the load support, the thermal conductivity, and the counterface compatibility. The filler content and dispersion determine the wear rate and the mechanical properties. The compaction and sintering process determines the porosity and the crystallinity, which affect the wear rate under load. The specification should include the filler system and content, the density and crystallinity, the mechanical properties, and the wear test method. The verification should include density, tensile, and wear tests. Ningbo Taifno PTFE Plastic Products Co., Ltd. has been manufacturing Modified PTFE Sheets for over 12 years and provides full material and wear test support for our customers.
