2.2 Measurement of coefficient of friction
The selected waxy materials were melted at 5 °C higher than their
melting point and pool into a cylindrical mold (40 mm in diameter × 25
mm in height). The molten waxes were allowed to solidify under room
temperature (23 °C) for 2 hours before removed from the mold. The wax
disc was then taped on the platform of a Discovery Hybrid Rheometer (TA
Instruments, New Castle, DE) equipped with tribo-rheometry accessories
for measurement of coefficient of friction. The test was conducted
following the procedures reported by Krasmik and Schlattmann (2015)
[9] except that a three-ball on plate setup (Figure 1) was used.
Normal load (FLoad), sliding velocity (υ) and
temperature were varied to determine their influence on friction and
wear behaviors of different waxes. The bottom surface of samples in
contact with glass were tested. When testing the effect of normal load,
normal load of 5, 10 and 15 N were used at a fixed sliding velocity of 5
rad/s under room temperature (25 °C). For evaluating the effect of
sliding velocity, 1, 5 and 10 rad/s were used with fixed normal load of
5 N under room temperature. For evaluating the effect of temperature,
environment temperature of 0, 25 and 50 °C were tested at fixed normal
load (5 N) and sliding velocity (5 rad/s). Three samples were prepared
for each test, and each sample was measured once.