Temperature Affects Materials Friction Coefficients
The state change of molecule motion of high polymer is called laxation according to the view of dynamics. The rising of temperature can improve heat movement ability of moving units on the one hand. On the other hand, because of thermal expansion, it increases molecule distance. Namely the internal freedom volume within the high polymer increases, which can increase activity space of moving unit, accelerate molecule movement, shorten relaxation time and expedite relaxation process. Following the relaxation of high polymer, its thermodynamics nature, viscoplasticity and other physical properties will also change dramatically. As one of the most frequently used indexes of mechanics, friction coefficient can also be influenced by the increase of temperature. Generally speaking, with the rising of environment temperature, surface friction coefficient of the material will have certain change, but changing amount will differ from material to material.
To verify the influence of temperature fluctuation on friction coefficient, the friction coefficient of several groups of material with certain representativeness are tested under different temperature. Detailed testing information and testing results are listed below:
Specimen: PC film, aluminum foil complex film
Instrument: Labthink FPT-F1friction coefficient /peel tester
Testing temperature: room temperature~90.0°C
Through testing, we can see that the rising of temperature has obviously influenced friction coefficient of material. But to different specimen, with the rising of temperature, the effects of influence are different. And to the same specimen, the variation tendency of kinetic friction coefficient will most likely be different from that of static friction coefficient. For example, to PC film, the growth trend for coefficient of static friction with the temperature rising is rather steady. But the variation tendency for coefficient of the kinetic friction is very great. However, the whole variation trend for kinetic friction coefficient also increases. As to aluminum foil compound film, growth trend of friction coefficient is not as obvious as that of PC film. And its coefficient of kinetic friction remains almost stable with the rising of temperature. One thing needs to be noted here is that when the testing is performed above 74 degrees Centigrade, obvious phenomenon of stick-slip will appear in the process of testing. That is to say the gliding is intermittent and not steady.
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