X2.2.5 Preheat Time—Proper preheat time is required to
allow the material in the barrel to fully melt and to come to
temperature equilibrium throughout the barrel. If material is
not fully melted, die plugging and low melt flow rates can
result. If not at temperature equilibrium, the melt flow rate will
change as the test is conducted.
X2.2.5.1 It is important that the die and piston be at
temperature equilibrium with the rest of the system before any
sample is introduced into the barrel. If the piston and die are
not at temperature, the large mass of metal involved must be
heated to temperature during testing and the energy required
may not allow the polymer to reach thermal equilibrium. This
can result in erroneous data.