Multistage Kinetic Model for Polyvinyl Butyral Synthesis

Abstract

Despite the high production volume and widespread use of polyvinyl butyral, its synthesis process remains insufficiently modeled due to the complexity of multistage kinetics and sequential phase transitions. In this study, we developed a multiscale, multistage model that integrates acetalization kinetics with a phase separation framework to capture the entire synthesis process, from the coil-to-globule transition and particle growth to the formation of a stable solid–liquid suspension. Validated against experimental data, our model reveals that chaotropic additives play a critical role in each stage of synthesis. During the transition stage, these additives accelerate acetalization by promoting an extended polymer conformation and reducing viscosity, which enhances n-butanal diffusion and delays nucleation. In the growth stage, low salt concentrations cause polymer collapse and reduced free volume, hindering diffusion; however, above a certain threshold, salt-induced disruption of polymer interactions leads to an expanded conformation, which improves mass transport. In the identification stage, PVB particles enter a glassy state where high salt concentrations rapidly increase acetalization levels, although the resulting rigidity limits further n-butanal penetration. This study provides a useful framework for optimizing PVB synthesis, with significant implications for improving material quality and production efficiency.