What is it about?

This paper is about the embrittlement mechanism in Polyethylene Terephthalate (PET) as a consecuence of hydrolysis. The study is undertaken in PET foams, but the results are valid for PET in other formats such as films or sheets.

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Why is it important?

Embrittlement involves loss of mechanical strength, and therefore the ductil-brittle transition point is taken as end-of-life criteria for materials with a structural function, such as PET foam. It has been well established that hydrolysis of PET leads to embrittlement, but the details of the embrittlement mechanisms were so far not fully understood, with most of the research efforts placed on the kinetics of the hydrolysis reaction and calculation and extrapolation of the activation energy (Ea). Experimental observations of hydrolysis of PET are undertaken at temperatures above its glass transition (Tg), while the use phase, in particular for structural applications, occurs below this temperature. Main questions so far was on the validity of Ea extrapolations to temperatures in the glassy state. Our results link embrittlement to the mobility of the PET molecules, questioning the occurance of embrittlement at temperatures below Tg.

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This page is a summary of: Hydrolytic Degradation of Closed Cell Polyethylene Terephthalate Foams. The Role of the Mobile Amorphous Phase in the Ductile-Brittle Transition, Polymer Degradation and Stability, August 2022, Elsevier, DOI: 10.1016/j.polymdegradstab.2022.110022.
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