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Disadvantages of PTFE

Time:2020/10/23 posted:Kehong Enterprises Co.,Ltd.

Although the performance of PTFE material is stable, its shortcomings are also obvious.

(1) Polytetrafluoroethylene has "cold flow". That is, the plastic deformation (creep) of material products under long-term continuous load, which brings certain restrictions to its application. For example, when PTFE is used as a gasket, the bolts are tightened very tightly for a tight seal, so that when a specific compression stress is exceeded, the gasket will produce "cold flow" (creep) and be crushed. These shortcomings can be overcome by adding appropriate fillers and improving the structure of parts.

(2) Polytetrafluoroethylene has a high melt viscosity and does not flow at high temperatures. It is above the melting point (327℃), and the melt viscosity reaches 1 010Pa.s. It does not flow even if heated to the decomposition temperature, which makes it impossible to use general thermoplastic molding methods, but to use sintering methods similar to powder metallurgy. forming.

(3) PTFE has outstanding non-stick properties, which limits its industrial application. It is an excellent anti-sticking material, and this performance makes it extremely difficult to bond with the surface of other objects.

(4) PTFE has low thermal conductivity and poor thermal conductivity, which not only prevents it from being used as a bearing material, but also prevents quenching when manufacturing thick-walled products.

(5) The linear expansion coefficient of PTFE is 10-20 times that of steel, which is larger than most plastics, and its linear expansion coefficient changes very irregularly with temperature changes. In the application of PTFE, if insufficient attention is paid to this aspect, it is easy to cause losses.

(6) When heated above 400°C, the cracking speed of PTFE gradually increases, and the decomposition products are mainly tetrafluoroethylene, perfluoropropylene and octafluorocyclobutane. Above 475°C, the decomposition product has a very small amount of highly toxic perfluoroisobutene. Note that the heating temperature should not exceed 400°C, and the laboratory should have a good ventilation system to help eliminate toxic gases.




(2)聚四氟乙烯的熔体粘度很高,在高温下也不流动。它在熔点(327℃)以上,熔体粘度达到1 010Pa.s,即使加热到分解温度也不流动,这就使它不能采用一般热塑性塑料的成型方法,而要采用类似粉末冶金那样的烧结方法成型。





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