March 3, 2005
Section 12, R&D Division 1
A&D Company, Limited

Measuring the Moisture Content of PBT Pellets with the MS70
Polybutylene terephthalate, abbreviated PBT, is a straight-chain thermoplastic
polyester that has an ester linkage in its main chain. PBT is a polymeric resin thatbelongs to the same family as PET.
1. Determining the Sample Quantity
As the moisture content of the PBT used for the present report was less than 0.1%,
the sample mass was set to 20g in accordance with Section 5.3.1 of the instruction
manual, “Necessary Mass for Measurements.”
Estimated Moisture Content

Necessary Mass for Measurement

1%->

At least 2g

0.5%->At least 5g

0.1%->At least 20g(Note: The larger the error of measurement the smaller the sample quantity)
2. Determining the Drying Temperature
The optimal drying temperature was determined using the RsTemp function of thestandard software WinCT-Moisture. In general, the moisture content of a resin material
is small and difficult to volatilize. Therefore, the graph curve is slow to stabilize and it ishard to judge whether water or another constituent is vaporizing.
The graph below appears to stabilize at 180˚C. However, a slight odor was generated
and the sample started to melt at around 200˚C. Consequently, based on overall
considerations, 160˚C was chosen as the drying temperature.

(Graph 1)
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Measurement Results
Below is an explanation of Graph 2:(1) The three measurement results above 0.08% were obtained from samples thatwere not subjected to pre-heating. They were stored in a room with humidity
around 30%RH.
(Automatic mode: Drying temperature 160˚C, Termination value 0.005%,Sample mass 20g, Measurement interval 10 minutes).
(2) The three measurement results below 0.04% were obtained from samples that
had been subjected to preliminary heating once before the measurements. Thesamples were considered to have been dried.
(Timer mode: Drying temperature 160˚C, 8 minutes, Sample mass 20g,
Measurement interval 10 minutes)

(Graph 2)(3) For your reference in the event that the pellets are left in a room of
23˚C/45%RH for 3 days (see Graph 3).

(Graph 3)
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Discussion and Recommendations for Accurately Measuring PBT Pellets(1) If the analysis mode of the MS70 is set to the “Standard Mode,” even when theaccuracy setting is HI (0.02%), it is hard to remove the moisture content, andthe measurement will be terminated in one minute, around 0.01%. Therefore,
more accurate results will be obtained if the measurement time is preset in the“Timing Mode.” The measurement conditions should be the same each time.
(2) In the event that the absolute value of the measurement results is different
from those of a Karl Fischer moisture analyzer, it is possible that a constituent
other than water is vaporizing. It is recommended that the drying temperatureand measurement time are set so that there is a correlation between the resultsof the two methods.
To correlate the results of the MS70 with those of a Karl Fischer moisture
analyzer, conduct both measurements in the same location simultaneously.
Depending on the storing environment, the samples may absorb moisture (Seethe measurement results in Graph 3).
(3) When the moisture content reaches below 0.1%, the influence of errors by themoisture analyzer become more significant, not to mention that ofenvironmental factors (humidity). For instance, a moisture content of 0.02%
means that a mass change of 0.004g has to be detected when the sample mass is20g (and only a 0.001g mass change for a 5g sample mass). Therefore, the larger
the sample mass the more accurate the measurement.
(4) When measurements are done in succession, the temperature around thesample pan increases, which volatilizes some of the sample’s moisture before
starting a subsequent measurement, thereby causing more errors. It is highly
recommended that a cooled pan be used each time and that measurement
intervals of approximately 10 minutes be taken to lower the temperaturearound the pan and maintain an equal temperature distribution for eachmeasurement.