Melt Intrinsic Viscosity (IV)
| Sample Type | Required Quantity | Equipment Used |
| Resin Flake Preform Bottle |
100 grams | Rheometer Karl Fischer Moisture Analyzer |
Purpose
This test measures the melt viscosity of the PET sample and calculates
the Intrinsic Viscosity value by correlation of the MIV to known SIV
values. Standard curves are created for specific resins. It is best to
measure a given company's resin using a calibration curve created from a
range of IV samples made by that manufacturer. If a calibration curve
for a specific resin is not available a "generic" calibration curve can
be used to predict the IV result.
Description
Resin samples can be analyzed directly, but preforms and bottles must
first be ground to a particle size that can be loaded into the
rheometer. All samples are dried overnight to remove water. The test is
run by packing the rheometer melt chamber quickly with the dried PET
sample under a stream of nitrogen. After a preset heat soak time, the
capillary rheometer is started causing the resin to be pushed through a
small orifice. The force required to make this happen is recorded. After
each sample has been pushed through the orifice, the melt chamber is
cleaned and reloaded from the same sample lot. This process is repeated a
total of four times with data being obtained from the last three
loadings. The average of these three force readings is then used to
predict the IV using the calibration chart. The result is also corrected
for the residual amount of moisture left in the samples at the time the
test is run.
Video Demonstration
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