Coefficient of Friction Testing


This procedure determines the coefficient of friction between two PET film samples using an adapted version of ASTM D1894-90.


Bottle samples are prepared and handled with gloves during both injection and blow molding to prevent contamination that might affect the COF results. The bottle sidewalls are cut from the bottle and one sidewall is mounted to a metal sled while the other sidewall is mounted to a flat plane. The COF assembly is then attached to the Instron machine and the force required to move the sled across the plane is measured using the 10lb load cell. The data is plotted as force (lbs) vs. the sled travel (in.) and is typically reported graphically. Our typical test usually results in a series of static COF values rather than an initial static value followed by a kinetic value; this is because our samples usually “jump” across the sidewalls rather than pull uniformly. The COF value is calculated by dividing the measured force by the weight of the sled.