SLIDING FRICTION CAN HOLD SOME SURPRISES
Most polymers are smooth to the touch and have a consistant feel about then. However, when the friction charateristics are analysed, the variation in the friction values can sometimes come as a surprise. This appears to be more so in thinner extruded film materials.
The average coefficient of friction value is naturally of interest, but when design considerations are being investigated, it is more critical to look at the maximum and minimum values and this can only be done by looking at a dynamic profile like the graph shown opposite. It is always good practice to repeat the test at least three times to check the consistancy of the material under investigating.