Polymerization and Collision in High Concentrations for Brownian Coagulation

Aggregation always occurs in industrial processes with fractal-like particles, especially in dense systems (the volume fraction, ϕ>1%). However, the classic aggregation theory, established by Smoluchowski in 1917, cannot sufficiently simulate the particle dynamics in dense systems, particularly those of generat ed fractal-like particles. In this article, the Langevin dynamic was applied to study the collision rate of aggregations as well as the structure of aggregates affected by different volume fractions. It is shown that the collision rate of highly concentrated particles is progressively higher than that of a dilute concentration, and the SPSD (self-preserving size distribution) is approached (σg,n≥1.5). With the increase in volume fraction, ϕ, the SPSD broadens, and the geometric standard is 1.54, 1.98, and 2.73 at ϕ= 0.1, 0.2, and 0.3. When the volume fraction, ϕ, is higher, the radius of gyration is smaller with the same cluster size (number-based), which means the particle agglomerations are in a tighter coagulation. The fractal-like property Df is in the range of 1.60–2.0 in a high-concentration system. Knowing the details of the collision progress in a high-concentration system can be useful for calculating the dynamics of coagulating fractal-like particles in the industrial process.

Microgel-like aggregates of isotactic and atactic poly(methacrylic acid) chains in aqueous alkali chloride solutions as evidenced by light scattering

We study the structure of aggregates formed by isotactic and atactic poly(methacrylic acid)s in aqueous solutions with added alkali chlorides using light scattering.

Preliminary Research on Particle Size Analyses Method of the Quicklime-Stabilized Dredged Material

The paper presents a comparative study of particle size analyses of quicklime-stabilized dredged material (LSDM) by combined sieve-hydrometer method (SHM), laser diffraction method (LDM) and sieve method (SM). After analyzed the testing processes and compared the results comprehensively, some conclusions can be conduction. Adopting SHM and LDM to test the particle size of LSDM, not only break the structure unit of soil, but also change its property due to the pure water used as disperser. In addition, the severe flocculation, which attributed to the dissolvable salt in soil introduced by quicklime can’t be drainage effectively, result in the abnormal particle size distribution (PSD) curves produced by the SHM. Therefore, SHM and LDM are not suitable for the particle size analyses of LSDM. SM, without deteriorating the unit structure of aggregates and altering the properties of soil, should be adopted as the most suitable method for LSDM.