(237d) Degradation of a Thermoplastic Polyether Ester Elastomer in Downhole Conditions

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Thermoplastic elastomers (TPEs) combine the strength of thermoplastics with the flexibility of elastomers, a characteristic potentially useful in downhole applications.  We studied the degradation process of a particular TPE of interest from both a mechanical and chemical perspective, and have determined the Fickian diffusion constant, the chemical degradation rate, the change in crystallinity, and the storage modulus with respect to varying temperature and time. Techniques used to determine such rates include: dynamic mechanical Aanalysis (DMA), differential scanning calorimetry (DSC), and end group analysis. Applying Arrhenius’ empirical relationship to the determined rates gives rise to a temperature-dependent model that predicts the degradation behaviour of the TPE outside of the experimental temperature range. Our results indicate that the chemical degradation via hydrolysis follows pseudo first order kinetics, and the degradation results in an increase of crystallinity and thus storage modulus and a decrease of tensile strength and strain.  The polymer eventually deteriorates due to brittleness.