pH-Induced Aggregation Mechanism and Attachment Efficiency Prediction of Acid Agglomeration in Polybutadiene Latex

Although acid agglomeration is widely employed in industry to rapidly enlarge the polybutadiene (PB) latex particle size by pH adjustment, the microscopic behavior and mechanistic basis of pH-induced PB aggregation remain insufficiently elucidated. This study employed time-resolved dynamic light scattering to quantitatively analyze the aggregation kinetics of PB particles under varying pH conditions and computed interparticle interaction energies using the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. Results indicate that reducing the pH diminishes the surface charge of PB particles, consequently eliminating the repulsive energy barrier between particles. Therefore, this study proposes that the transition between aggregation and stability is dictated by the protonation equilibrium of dehydroabietic acid adsorbed on PB surfaces. Under acidic conditions, protonation of carboxyl groups reduces the surface charge density and enhances aggregation by strengthened hydrogen bonding. In alkaline environments, charged carboxyl groups dominate, increasing electrostatic repulsion and particle stability. Furthermore, in the research on predicting the aggregation behavior of PB particles, it was discovered that the Maxwell model outperformed the 1/W model in reaction-limited regimes due to its explicit incorporation of particle kinetic energy distribution. This work elucidates the microscopic mechanism behind the pH-induced aggregation of PB and formulates a predictive framework for attachment efficiency, thereby enabling precise optimization of the acid agglomeration process.