Influence of Shear Flow in High-Temperature Crystallization of PPTA/Sulfuric Acid Solutions

In our previous studies, we observed the irreversible crystallization of poly(p-phenylene terephthalamide) (PPTA) solutions at high temperatures, attributable to phase separation induced by weakened hydrogen bonds. In this study, we introduce continuous shear flow to investigate flow-induced crystallization or phase separation behaviors. We found that shear flow progressively reduces the degree of crystallization with increasing shear rate. We attribute this reduction to flow-induced suppression of phase separation; the flow field competes with (and can overwhelm) the diffusive/coarsening dynamics that normally amplify composition fluctuations, thereby undermining the precondition for crystallization acceleration-i.e., an increase in the local PPTA concentration.