Degradation before dehydration

PPS. Polymer is recovered by washing with water to remove the salt and solvent, and then dried. The pol)merization (Eq. 1) is very sensitive to many process variables that must be monitored to avoid polymer degradation. Molecular weight of the PPS can be increased by adding sodium acetate or other alkali metal carboxylate salts to the polymerization mixture before dehydration. Also, a small amount of a trifunctional comonomer, such as 1,2,4-trichlorobenzene, can be added with the dichlorobenzene as a chain branching agent. 

Before or simultaneously to the chemical lesion induction, these very concentrated corrosives can cause a ceU necrosis by dehydration and/or by thermal effect. Once more, this justifies the necessity to wash as soon as possible and to optimize the decontamination. This includes washing and physical mechanical rinsing in a better control of the dangerous potential degradation products of the chemical reaction. 

Under heated or hydrothermal conditions, the possible degradation mechanism for AEMs has been discussed in the literatures. Hydrolytic stability of the AEMs is performed by treating the membrane in hot water for a specific period. Only a few reports are concerned with the hydrolytic stability so far. For Watanabe research gronps, they performed the hydrolytic stability test in hot water at 80 C for 500 h the chemical structures before and after the hydrothermal test were analyzed by the use of H NMR spectra. A long-term hydrothermal test was also performed for 5000 h, and the ionic conductivity was used to assess the stability. According to their results, the major degradation mode of the AEM (based on quaternary PES) under the hydrothermal condition is most likely to be the elimination of a tertiary amine to form benzyl alcohol and its further decomposition via dehydration. ... 

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