Macromolecular Reaction Engineering最新文献

An exploratory study on the possibility of developing bimodal PVC microsuspensions via the in situ generation of small particles in the presence of a large microsuspension seed is presented in order to reduce the number of process steps. The in situ nucleation step was investigated using 3 different redox initiators, and the final products were compared to the reference product made by mixing 2 seeds and copolymerizing them to increase the solid content. It was found that while none of the alternatives considered allowed to reproduce the exact PSD of the reference system, a redox system based on a combination of ammonium persulfate and Iron (II) sulfate came the closest to the reference product. It enabled us to generate well-defined small particles in the right size range. The other systems that did not generate enough negatively charged free radicals led to poorly defined small particle populations.

In the commercial production of acrylic and vinyl polymers, trace amounts of oxygen can significantly disrupt free-radical polymerization by generating toxic volatile organic compounds (VOCs), retarding polymerization, and altering polymer properties. To establish a mechanistic understanding of these effects across industrially relevant monomers, this work examines the influence of oxygen on the solution homopolymerizations of butyl acrylate (BA), vinyl acetate (VAc), and methyl methacrylate (MMA). Systematic experiments conducted under nitrogen and air reveal pronounced monomer-dependent behavior: BA and VAc exhibit severe retardation and form only oligomeric species, while MMA continues to polymerize but shows substantial reductions in molar mass. In all three systems, the presence of oxygen promotes the formation of toxic VOCs, with the extent of oxidation increasing sharply as monomer concentration decreases. To complement the experimental findings, a mechanistic kinetic model is developed for MMA, enabling prediction of monomer conversion, VOC formation, and molecular-weight evolution under oxygen-containing conditions. Together, this work provides a unified framework for understanding oxygen-induced defects in industrial free-radical polymerization processes involving acrylic and vinyl monomers.

A fault detection system based on a recurrent autoencoder is proposed, suitable for continuous processes with complex nonlinear dynamics. The system consists of three modules: 1) a recurrent autoencoder; 2) a fault state detection module; and 3) an interpretation module. The training strategy only requires process data obtained under normal operating conditions. The fault detection module analyzes the total reconstruction error of the measured variables obtained by the recurrent autoencoder. The interpretability module examines the reconstruction errors of the individual variables and highlights variables potentially responsible for the detected anomaly. The developed system is applied to a computationally simulated Styrene-Butadiene rubber latex production process. The latex is synthesized in a train of continuous stirred tank reactors that may be affected by various types of faults. Simulation results show a satisfactory performance of the proposed fault detection system. Failures whose data patterns differ significantly from those of normal operation are effectively detected. In contrast, some subtle faults only cause minor deviations in the data patterns and are therefore difficult to detect rapidly, leading to delays in detection. In most cases, the interpretability module can correctly identify the variable more strongly associated with the detected fault.

The primary synthesis of liquid rubber via anionic polymerization requires substantial alkali metal initiators, resulting in high costs. This study introduces a metal-free chain transfer agent (CTA), 9,10-dihydroanthracene (DHA), into the anionic polymerization of isoprene (Ip). A series of liquid polyisoprenes (PIp) with number-average molecular weights (M_n) ranging from 2100 to 6800 g/mol were synthesized. Furthermore, the correlation between DHA, THF dosage, and reaction temperature and the resulting polymer structures was established. The results indicate that at 20°C, DHA induces chain transfer during the anionic polymerization of Ip. Moreover, higher dosages of both DHA and THF led to lower M_n and polydispersity index (PDI) of the resulting PIp, corresponding to a lower degree of polymerization ($�{\overline{X}}_n$). Concurrently, the initiator efficiency (E_I) and chain transfer constant (C_M) increased. Conversely, −25°C effectively suppressed chain transfer, while 60°C did not significantly promote the process. To validate its practical potential, a 100-fold scale-up experiment was performed. This yielded a series of liquid PIp with M_n below 2500 g/mol, PDI below 1.21, E_I greater than 20.0, and C_M greater than 2.8 × 10⁻². It provides crucial theoretical and experimental foundations for advancing the preparation technology of liquid rubber.