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1.4 EQUIPMENT USE
The "Incoming" or "Supplied" Resin can be checked before acceptance of delivery.
The "Dried" resin can be checked daily from the drying hopper to check the efficiency of the drying
heaters and / or drying desiccant.
The preforms can be checked before and after storage to monitor the IV drop in the extruder and also
to check the suitability of the storage area (humid storage conditions will reduce the IV of the preform
and cause problems during the blow moulding stage).
Note that the drier and preforms CANNOT be checked using the solution method because this checks
the IV of the polymer and NOT the changes in IV due to the production process.
The PET Plus also reports the Thermal Degradation Factor, which is a combination of the Thermal
Degradation Rate and the Hydrolytic Degradation Rate.
It is found in practice that the IV drop from polymer chip to preform is usually in the range of 0.02 to
0.03 IV.
1.5 MEASUREMENT RANGE
The IV measurement range is approximately 0.45 to 1.40 using dies from 0.015 in (0.0381cm) to
0.040 in (0.1916cm).
Every die is machined to be 0.5 in (1.27cm) long and has a very accurately defined bore. Each die is
supplied with a calibration certificate, which states the exact size of the die, and these values are to
be entered into the test parameters.
The software calculates Intrinsic Viscosity (IV) and the degradation rate according to the ICI algorithm
for PET.
Although primarily designed to test hygroscopic polymers in an oxygen and water free environment,
the flow properties, viscosity and degradation of most polymers may be tested.
The range of IVs that can be measured using the available dies is shown below:
Die
Size
15 thou
20 thou
30 thou
40 thou
8 PET Plus User Manual
Die
Internal
Diameter (cm)
0.0381
0.0508
0.0762
1.1016
IV Range
at
284ºC
0.43 to 0.62
0.53 to 0.70
NA
NA
IV Range
at
295ºC
NA
0.70 to 0.83
0.74 to 1.14
0.93 to 1.43
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