When you are choosing the right PEEK composite material, you always get into trouble and don’t know which material to choose. Today we will compare unfilled peek and carbon fiber peek to improve your knowledge of peek materials.
Unfilled PEEK is a 100% pure resin high-performance thermoplastic polymer without any fillers or reinforcements. It is beige or natural in color at room temperature and can be made into various semi-finished profiles, such as PEEK sheets, peek rods, peek pipes, etc. It has the highest elongation and toughness, excellent mechanical and chemical properties, and is suitable for applications that require chemical stability and FDA compliance. It can be used continuously in high-temperature environments of 250°C.
Carbon filled PEEK is referred to as CF PEEK. Different proportions of carbon fiber, such as 10%-30%, are added to the unfilled peek to make the peek have better performance. Of course, the performance will be different if different proportions are added.
We usually use 30% carbon fiber as a reference. The color of Carbon filled PEEK is usually black. Compared with unfilled peek, Carbon fiber PEEK significantly improves the compressive strength, stiffness, and wear resistance, reduces the thermal expansion coefficient and increases the thermal conductivity. It is very suitable for applications that require high strength and high wear resistance. And high thermal stability accessories.
| Property | Unfilled PEEK | Carbon Filled PEEK | Results |
| Density | 1.31 g/cm³ | 1.41 g/cm³ | / |
| Tensile Strength | 16,000 psi (110 MPa) | 19,000 psi (131 MPa) | Carbon filled PEEK |
| Tensile Modulus | 500,000 psi (3,448 MPa) | 1,100,000 psi (7,586 MPa) | Carbon filled PEEK |
| Flexural Strength | 25,000 psi (172 MPa) | 25,750 psi (177 MPa) | Carbon filled PEEK |
| Flexural Modulus | 600,000 psi (4,137 MPa) | 1,250,000 psi (8,620 MPa) | Carbon filled PEEK |
| Compressive Strength | 20,000 psi (138 MPa) | 29,000 psi (200 MPa) | Carbon filled PEEK |
| Heat Deflection Temperature | 162 °C | 291 °C | Carbon filled PEEK |
| Water Absorption | 0.001 | 0.0006 | Carbon filled PEEK |
| Coefficient of Thermal Expansion | 2.6 x 10^-5 in/in/°F | 1.0 x 10^-5 in/in/°F | Carbon filled PEEK |
| Wear Resistance | Moderate | Excellent | Carbon filled PEEK |
| Electrical Conductivity | Insulating | Conductive | Carbon filled PEEK |
| Chemical Resistance | Excellent; resistant to most chemicals and solvents | Excellent; similar resistance with enhanced durability | Carbon filled PEEK |
| Electrical Insulation | Excellent; high dielectric strength | Moderate; improved conductivity due to carbon content | Carbon filled PEEK |
| Thermal Conductivity | Low (~0.25 W/m·K) | High (~3.5 times that of unfilled PEEK) | Unfilled PEEK |
| Elongation at Break | 0.2 | 0.05 | Carbon filled PEEK |
| Thermal Properties | Max Service Temp: 480°F (250°C) | Max Service Temp: 600°F (316°C) | Carbon filled PEEK |
| Hardness | Rockwell M100 | Rockwell M102 | Carbon filled PEEK |
| Flame Retardancy | UL 94 V-0 | UL 94 V-0 | SAME |
| Friction Coefficient | ~0.25 | Lower due to carbon; ~0.05 under lubricated conditions | Carbon filled PEEK |
| Resistivity | High resistivity | Lower resistivity due to carbon content | Carbon filled PEEK |
The tensile and compressive strength of the carbon-filled PEEK is found to be higher than that of unfilled PEEK because of the strength imparted by carbon fibers. This makes Carbon filled PEEK ideal for use in applications where high loading is expected.
The tensile modulus and fused modulus of carbon fiber PEEK30 are much higher than that of the unfilled PEEK which shows the enhanced rigidity of the carbon fiber-reinforced PEEK30 against deformation at stress.
carbon fiber PEEK30 has significantly higher HDT, thus it is better for high-temperature applications where component strength plays a vital role.
This feature brings wear resistance in carbon fiber PEEK30 which is useful where there are mechanisms that slide or rotate.
Two analyzed materials demonstrate high chemical resistance; yet, slightly lower water absorption in carbon fiber PEEK30 may be an advantage in humid conditions.
The unfilled PEEK material exhibits a lower coefficient of thermal expansion than that of the carbon fiber PEEK30 thus it can provide dimensional stability in the temperature changes.
| Application Area | Unfilled PEEK | carbon fiber PEEK |
| Medical | Used in implants and surgical tools | Suitable for high-strength implants |
| Examples: Spinal fixation devices, dental implants | Joint replacement implants | |
| Aerospace | Used in electronic components and thermal insulation | Ideal for lightweight, high-strength structural parts |
| Electrical connectors in aircraft | Wing brackets | |
| Automotive | Used in seals, valves, and pumps | Suitable for high-load components like gears |
| Fuel pump seals | High-performance bearings in racing cars | |
| Food Processing | FDA compliant for food contact applications | Used in high-load food processing equipment |
| Examples: Filling nozzles, mixing paddles | Valve components in high-temperature food processing | |
| Semiconductor & Electronics | Used in wafer processing tools | Used in high-performance electronic components |
| Tools for chemical mechanical polishing | Connectors and heat sinks | |
| Oil & Gas | Used in seals and electrical connectors | Suitable for critical components in harsh environments |
| Electrical insulation materials in wells | High-pressure valve components |
Comparative table that analyzes the difficulties that arise when using unfilled PEEK and carbon-filled PEEK , especially where the properties of carbon fiber PEEK are superior to those of conventional PEEK.
| Aspect | Unfilled PEEK | CF PEEK |
| Machining Process | Easier to machine with conventional tools | Requires specialized tools (e.g., diamond tools) for precision machining due to increased hardness |
| Cooling Requirements | Standard cooling methods (liquid coolants) can be used | Pressurized air is preferred to avoid contamination and maintain biocompatibility |
| Processing Temperature | Melt temperature: 350°C to 400°C | Similar melt temperature, but requires careful monitoring to prevent degradation |
| Elongation and Toughness | Higher elongation allows for easier handling | Lower elongation; more prone to cracking if not handled carefully during machining |
| Annealing Needs | May require annealing to relieve internal stresses | More critical to anneal due to susceptibility to stress cracks and deformation |
| Tool Wear | Standard cutting tools are sufficient | Higher tool wear due to abrasive nature; may require more frequent tool changes |
| Injection Molding | High flow properties facilitate easier molding | Poor flow properties; requires higher injection pressures and longer cooling times |
| Shrinkage Rate | Moderate shrinkage | Lower shrinkage, but high filler content can lead to warping if not managed properly |
| Surface Finish | Good surface finish achievable | Achieving a high-quality surface finish is more challenging due to the material's rigidity |
The two sub-types of PEEK are carbon fiber reinforced PEEK and Unfilled PEEK, which both belong to the category of high-performance thermoplastic polymers. Although they have many characteristics in common they are different in some ways and they have properties that make them ideal for particular uses.
If you have any questions about Unfilled PEEK & carbon fiber PEEK, please contact us and we will answer them for free.
Zhejiang Bw Industrial invested 15 million yuan in the newly built PEEK application technology research and development center, which has been put into use. With the help of this research and development center, our technical personnel can provide many technical services for the PEEK industry, mainly including:
