Elastomer Degradation in Chemically Reactive Environment under Elevated Temperature and Pressurized Condition




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Mechanical properties of elastomer undergo accelerated degradation when immersed in chemically active environment, especially at elevated temperature and/or under high pressure. Beside physical relaxation due to the viscoelastic nature of polymers, diffusion-reaction process plays an important role in accelerating elastomer deterioration. In a previous research, Fickian diffusion was often used to model the small molecule ingression in bulk elastomeric materials. Under high temperature and high pressure, chemical reaction accelerates and some of the processes that are negligible under standard temperature and pressure can have significant impacts on elastomer properties. For example, water near or above its critical state, can react with some relatively stable functional groups in elastomers. To study elastomer degradation under HPHT and chemical environment, sealed mechanical testing apparatuses have been designed and manufactured so that real time mechanical performance of elastomer under compression after ageing in chemicals, at elevated temperature, and under pressurized conditions, can be quantitatively studied. It is found that for elastomer stress relaxation, additional lateral confinement induced by environmental stress can effective reduce elastomer relaxation along the axial direction. In addition to the development of experimental elastomer characterization methodology, we also built a quantitative model to investigate the diffusion-reaction process between chemical diffusant and elastomer at elevated temperature and under pressurized condition. The PDE developed in this study uses the Vrentus-Duda free volume theory to quantify the diffusion between small molecules and macromolecular matrices. Current model allows us to study temperature, pressure, and chemical kinetic effects through the quantification of diffusant concentration profile evolvement numerically by solving the PDE problem. Finally, we also studied the electromechanical properties of an elastomer-carbon nanocomposite. The nanocomposite are fabricated by a solution casting technique based on a patent from our research group to achieve high quality interfacial bonding and uniform filler distribution. Electromechanical behavior in such elastomer nanocomposite is studied, repeatable piezoresistive response is confirmed after training cycles, and their potential applications as large deformation strain sensor are discussed.



Elastomer, Ageing, Diffusion-reaction process, Free volume theory, Affine network model