Polytetrafluoroethylene (PTFE) is valued for its exceptional chemical inertness, low friction coefficient and wide operating temperature range. However, unfilled PTFE has significant limitations for engineering applications: poor thermal conductivity (only 0.25 W/mK), high creep under sustained load, and relatively rapid wear under sliding contact. Bronze powder - typically CuSn10 atomised powder in the 10-45 micrometre range - is one of the most established and effective fillers for overcoming these limitations. Bronze-filled PTFE compounds are widely used in bearings, seals, piston rings, valve seats and guide rings across chemical processing, food and beverage, pharmaceutical, oil and gas, and general industrial machinery sectors.
Why Bronze Is the Preferred PTFE Filler for Bearing Applications
Bronze powder improves PTFE performance in three critical areas simultaneously. First, thermal conductivity: bronze-filled PTFE (typically 40-60% by weight) achieves thermal conductivity of 0.8-1.2 W/mK - a 3-5x improvement over unfilled PTFE. This allows heat generated by friction to dissipate through the bearing wall rather than accumulating at the sliding surface, preventing thermal degradation and extending service life. Second, creep resistance: bronze particles act as a rigid skeleton within the PTFE matrix, dramatically reducing cold flow under sustained compressive load. This is essential for dimensional stability in seal and bearing applications where tight tolerances must be maintained over years of service. Third, wear resistance: the bronze particles carry a proportion of the contact load, reducing the wear rate of the PTFE matrix by factors of 100-1000x compared to unfilled PTFE, depending on operating conditions. MEPOSO supplies CuSn10 bronze powder specifically graded for PTFE compound production, with controlled particle size distribution, consistent tin content and low oxide levels.
Particle Size and Morphology Requirements for PTFE Compounding
The particle size distribution of the bronze filler has a direct impact on compound processability and final part performance. Particles that are too coarse (above 75 micrometres) create stress concentration points in the PTFE matrix, can damage the counterface in bearing applications, and produce surface roughness that increases friction. Particles that are too fine (below 5 micrometres) tend to agglomerate, making uniform distribution in the PTFE difficult and creating localised filler-rich zones that can initiate cracks under cyclic loading. The optimal range for most PTFE bearing and seal applications is D50 of 15-25 micrometres with D90 below 45 micrometres. Spheroidal gas-atomised particles are preferred over irregular water-atomised particles because they distribute more uniformly in the PTFE matrix, produce lower internal stress in the compacted preform, and result in more consistent mechanical properties in the finished part.
Bronze Loading Levels and Their Effect on Properties
The proportion of bronze powder in the PTFE compound determines the balance between improved mechanical properties and retained chemical/friction characteristics. At 15-25% bronze loading, the compound maintains good chemical resistance and a relatively low friction coefficient while gaining modest improvements in thermal conductivity and creep resistance. This range is common for chemical processing seals and food-grade applications. At 40-60% bronze loading, thermal conductivity and mechanical strength increase substantially, making the compound suitable for heavy-duty bearings, piston rings and structural components. However, the friction coefficient rises and chemical resistance decreases as more bronze surface is exposed to the environment. Above 60% loading, the compound becomes increasingly metallic in character and may lose the key PTFE advantages. MEPOSO provides application-specific guidance on optimal loading levels based on the end-use requirements.
MEPOSO Bronze Powder for PTFE Applications
MEPOSO S.r.l. manufactures CuSn10 and CuSn8 bronze powders specifically optimised for PTFE compound production. Our bronze powders are gas-atomised for spheroidal morphology, graded to tight particle size specifications (typically -45 micrometres with controlled D50), and produced with consistent tin content verified by XRF analysis on every batch. Low oxide content is maintained through controlled atomisation atmosphere and proper storage, ensuring clean particle surfaces for optimal bonding with the PTFE matrix. Every production batch is accompanied by certificate of analysis, particle size distribution report and safety data sheet. Contact MEPOSO to discuss your PTFE compounding requirements and request technical samples.
Contact MEPOSO for CuSn10 bronze powder for PTFE compounds, technical data sheets and application guidance.
