Fundamental modeling and experimental investigation of polymer washing batch process

Abstract

After polymerization reaction, impurities composed of adduct, used solvent and catalyst remain inside the formed polymers. These impurities should be removed by washing to improve the purity of the polymers. In this process, the model of the polymer washing process is essential to optimize the energy, resources and operating time. This work proposes a fundamental model of polymer washing process to provide theoretical basis for optimization. The model describes the impurity distribution inside the polymers using pseudo steady state approximation with the concept of moving boundary of diffusion. Also, the impurity diffusion at polymer surface is described with Fick's law. In addition, this work reports an experimental investigation of polymer washing process using SPAEK (sulfonated poly(aryl ether ketone)) samples. In the investigation, impurity diffusion coefficient at polymer surface of the experiment is computed from the pH data. The computed D have different values for each operation, as a lumped parameter. However these values show the same trajectory with the introduction of a dimensionless number Co for each operation. This means other impurity diffusion factors, not included in the model, embraced in D are only affected by Co, even if the initial impurity concentrations inside the polymers are different for each operation. Finally, we predict the pH changes in a different experimental condition, and validate the prediction performance of the model.