Polyurea nanofibers, of high thermal stability and solvent resistance, were obtained through simple precipitation polymerization of TDI and ODA in acetone at 30 °C.
A series of poly(styrene-co-methacryloxyethylhexadecyldimethyl ammonium bromide), P(St-DMHB), cationic particles were prepared by emulsion polymerization using 2,2 0 -azobis(2-methylpropionamide) dihydrochloride as the initiator with different levels of DMHB as the cationic functional comonomer. f potential, particle size, and size distribution of the particles were determined. Large discrepancy was observed between the particle size from dynamic light scattering and that from transmission electron microscopy. Results showed that particle size and f potentials were closely dependant on DMHB level used. A flocculation process for the cationic latex was established, and a method to estimate DMHB conversion was proposed.
The computational fluid dynamics (CFD) and kinetic-based moment methods coupled approach is adopted to simulate the bulk copolymerization of styrene-acrylonitrile (SAN) in a stirred tank reactor. Numerical simulations are carried out to investigate the impacts of impeller speed, monomer ratio, initiator ratio, and initial reaction temperature on the copolymerization process and product properties. Particularly, the Chaos theory is selected as a criterion for evaluating the occurrence of the thermal runaway. The Flory's and Stockmayer's distributions are employed to calculate chain length distribution and copolymer composition distribution of copolymer. The simulation results highlight that the appearance of thermal runaway can be postponed by properly increasing the rotation speed, decreasing the initiator loadings, initial acrylonitrile contents and initial reactor temperature. Furthermore, significant differences exist in the product properties that predicted by the ideal and non-ideal models, which demonstrates that the temperature heterogeneity plays a crucial role in SAN copolymerization. This study could offer references for the safe operation and design of polymerization processes.
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