1. Difficulty in processing and molding: PTFE cannot be molded by conventional thermoplastic processes such as injection molding and extrusion because its melting point is as high as 327°C and its viscosity after melting is extremely high, similar to the rubber state. It usually requires special processes such as cold pressing sintering or machining, which makes the processing process complicated, the production efficiency is low, and the equipment and process requirements are high, which increases the production cost.
2. Insufficient mechanical properties
- Cold flow problem: PTFE has cold flow properties. When it is under pressure for a long time, it is easy to undergo plastic deformation, resulting in a decrease in sealing performance and affecting the service life and reliability of the valve. For example, in some working conditions that need to maintain a sealed state for a long time, PTFE valves may leak due to cold flow.
- Low wear resistance: Although PTFE has a low friction coefficient, it has poor wear resistance. Pure PTFE is easily worn during long-term use, especially in conditions with granular media or frequent switching. The wear will be more obvious, which will affect the sealing and service life of the valve.
- Low mechanical strength: The tensile strength and hardness of PTFE are much lower than those of metals or other engineering plastics, and it is not suitable for high-load scenarios. In some working conditions that need to withstand greater pressure or impact, PTFE valves may deform, crack, and other problems.
3. Thermal conductivity and thermal expansion problems
- Poor thermal conductivity: The thermal conductivity of PTFE is only 0.25W/(m·K), and its thermal conductivity is very poor, which can easily lead to local overheating. In some working conditions that require rapid heat dissipation or high temperature uniformity requirements, PTFE valves may experience problems such as thermal deformation and thermal fatigue.
- High thermal expansion coefficient: The linear expansion coefficient of PTFE is more than 10 times that of metal, and its dimensional stability is poor when the temperature changes. In an environment with large temperature fluctuations, PTFE valves may have problems such as poor sealing and loose parts due to thermal expansion, and sufficient expansion gaps need to be reserved during design.
4. Risk of high-temperature decomposition: PTFE has a low decomposition temperature. It will decompose when it exceeds 400°C, releasing toxic gases such as perfluoroisobutylene and hydrogen fluoride. Therefore, the operating temperature of PTFE valves usually needs to be strictly controlled below 260°C, and the long-term use temperature is generally recommended not to exceed 120°C, which limits its application in high-temperature conditions.
5. High cost: Due to the complex monomer synthesis process of PTFE, high processing energy consumption, and the production process requires special equipment and processes, its cost is relatively high. This makes PTFE valves face certain competitive pressure in some cost-sensitive projects.
6. Opacity: PTFE material itself is opaque and cannot be made into transparent products, which limits its use in some valve applications that require observation of internal medium flow or optical inspection.
7. Low temperature brittleness: Although PTFE has certain low temperature resistance, its impact strength will decrease at low temperatures, and brittle fracture may occur. In some applications in low temperature environments, PTFE valves need to be specially modified or corresponding protective measures need to be taken.