Hello and welcome to this post on design data for polymer material selection in which we discuss the hydrolysis resistance of high performance polymers. More plastics design data can be found in my “start here” section.
Hydrolysis resistance - the resistance to attack by water
In general, hydrolytic resistance can be defined as the resistance to attack of the polymer structure by water. Hydrolysis resistance is part of the chemical resistance spectra and is important since water is very aggressive to many polymers. There are different tests on the estimation of hydrolytic resistance. One quick test is the immersion of a plastic specimen in boiling water for several days. Another method is to place a specimen 3 hours long at 105°C or even 5 hours long at 121°C in the steam autoclave.
For example, the mechanism of hydrolysis of Polyester polymers (PET, PBT) is the reaction of water with ester groups at high temperature. Also with Polyamide 6, reaction with water at high temperature will result in a split into caprolactam and oligomers. Polyurethanes will split into polyols and amines at high temperature and water exposure.
Hydrolysis resistance data of high performance polymers
Table 1 shows the hydrolysis resistance data of high performance polymers and Figure 1 compares the hot water resistance of an aliphatic Polyamide 6.6 and a Polyphenylene sulfide (PPS) at 110°C and 6000 hours. Already around 2000 hours a delta of almost 10% can be seen which increases even more with time. Important for both material is that the glass fiber used has a hydrolysis resistant sizing.
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| Table 1: hydrolysis resistance data of high performance polymers. |
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| Figure 1: hot water resistance of a PA and a PPS, 110°C, 6000 hours. |
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Greetings
Herwig Juster
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Literature:
[1] Polytron - Materialeigenschaften Hochleistungskunststoffe
[2] https://www.solvay.com/en/brands/radel-ppsu
[3] Grivory HT - Enhanced properties at high temperatures
[4] https://www.curbellplastics.com/materials/applications/hydrolysis-resistant/
[5] https://www.fastradius.com/resources/hydrolysis-resistant-plastics/
[6] https://eu.mitsuichemicals.com/sites/default/files/media/document/2018/f-01-06_boiling_water_resistance.pdf
[7] http://www.bosy-online.de/Korrosion/Alterung_SA.pdf
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