(1) PTFE seals can only be manufactured by molding and squeezing process, and the molding is more difficult. The finished product must be reduced by the previous machine tool, which limits the effectiveness of the product.

(2) The Teflon seal has "heat flow". That is to say, the finished product is undergoing plastic deformation (creep) under the influence of continuous load, which gives it a certain limit. For example, when PTFE is used as a thin opening pad, the bolt is loosely tightened, and even when a specific tightening stress is exceeded, the gasket is "heat flow" (creep) and is crushed. Those defects can be overcome by participating in proper excavation and improving the whole structure.

(3) The melt viscosity of the PTFE seal is very low and there is no activity at low temperatures. It is melting above the surface (327 ° C), the melt viscosity reaches 1010 Pa.s, even if the heat is reduced to the differentiation temperature, there is no activity, so that it can not take the molding method of ordinary thermoplastics, but to adopt similar powder metallurgy Such a sintering method is formed.

(4) The PTFE seal has a convex and non-tacky property, which limits its industrial application. It is an excellent anti-stick material, which in turn makes it extremely difficult to stick outside the other objects.

(5) The thermal conductivity of the PTFE seal is low, and the heat transfer function is good, which not only hinders it from being used as the shaft start data, but also makes the thin wall finished product can not be quenched.

(6) The coefficient of linear shrinkage of PTFE seals is 10 to 20 times that of steel. Compared with most plastics, the linear shrinkage coefficient changes with temperature and produces very undisciplined changes. When PTFE is being used, it is easy to form a loss if it is not enough for the round machine.

(7) When the temperature is reduced above 400 °C, the cracking rate of tetrafluoroethylene is gradually accelerated. The important product of differentiation is tetrafluoroethylene, fluoropropene and octafluorocyclobutane. At 475 ° C or above, the differentiated products have a small amount of highly toxic fluoropropene and butene. Pay attention to the heat-reducing temperature can not exceed 400 ° C, and the laboratory should have a superior ventilation system, which is conducive to the elimination of toxic gases.