Predictive durability of polyethylene terephthalate toward hydrolysis over large temperature and relative humidity ranges

• Published in: Polymer (Guilford) Vol. 142; pp. 285 - 292
• Main Authors: Dubelley, Florence, Planes, Emilie, Bas, Corine, Pons, Emmanuelle, Yrieix, Bernard, Flandin, Lionel
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 25-04-2018; Elsevier BV; Elsevier
• Subjects: Biodegradation; Chain scission; Chemical reactions; Crystal structure; Degradation; Durability; Engineering Sciences; Humidity; Hydrologic data; Hydrolysis; Materials; Mathematical models; Melting; Moisture content; Organic chemistry; Polyethylene; Polyethylene terephthalate; Predictions; Relative humidity; Temperature effects
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2018.03.043

The hydrolytic stability of poly(ethylene terephthalate) (PET) has already been largely reported. The chemical reactions induced by damp-heat exposure are well–known, and various kinetic expressions for the degradation have been presented. Using the data from previous studies, a new model for degradation is proposed. This model combines the effect of temperature and humidity in a single equation. Three parameters are utilized: the classical pair of activation energy (Ea) and pre-exponential factor (f0), and the reaction order (n) to the relative humidity (RH). The model may be used to fit the degradation data from various sources describing the hydrolysis over a large range of conditions (40–100 %RH, 60–160 °C). In addition a prediction of the crystallinity changes brought about by hydrolytic chain scission was performed. Prediction of useful lifetime in moist heat is also possible (hydrolysis of 0.2% ester moieties in the polymer).
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•The Arrhenius law is extended to account for the detrimental effect of water.•The model properly fits the data obtained from a large literature mining.•The order of the hydrolytic reaction with respect to humidity is 1.5•A reasonable value is proposed for the activation energy of hydrolysis (100 kJ mol−1).•A single master curve allows to predict the end-of-life for all PET morphologies.