providing a window into the process
INTRODUCTION
A flow rate test is a measure of a polymer's mass flow rate (grams extruded in 10 minutes)
using a particular orifice under specified conditions of temperature and load. Machines that
determine flow rate are generally called Melt Indexers. Test methods by ISO, DIN, ASTM and
others specify heat chamber and piston tip diameter such that the shear stress on the polymer
is the same in all machines for a given load. In addition, material specification guidelines (by
ISO, DIN, ASTM, GM etc) may exist which give further constraints on how a particular type of
material may be run.
The tests performed are those described by ASTM D1238 and ISO 1133-1, 1133-2. This
manual in no way supersedes either of these documents. The precision and accuracy of the test
has been determined by ASTM method D1238. Contributing to both precision and accuracy are
operator variances such as; packing technique, cleaning, cutting, weighing etc. With moisture
sensitive polymers, dryness can also play a major role, and time can be a factor with thermally
unstable polymers, so procedures must be identical. Dynisco Polymer Test Systems has found
that charging a consistent mass of material into the barrel (±0.1 grams) is the most critical factor
in getting precise data.
Several methods have been developed for running flow rate tests under D1238, with Methods A
(mas
s of material over time) and B (volume of material over time) being the basic of all methods.
Method A is simply the collection of extrudate over time, while Methods B, C and D are the
measurement of time for the flow of a fixed volume of polymer. All but Method A require an
encoder to measure distance traveled to determine volume of material extruded during the test.
P/N: M0726(3) | Rev: 012020 | ECO: 51182
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