Primary properties particle size distribution

The most challenging part of rubber mixing is the dispersion of the filler The filler agglomerates have to be broken into smaller particles, the aggregates, but not completely to the level of primary particles. An optimal particle size distribution has to be achieved in order to obtain the best properties of the final rubber product [14]. 

Having defined particles and partical distributions, we now examine methods by which we can measure peuticles and properties of powders. There are four (4) primary methods used to obtain data concerning particle size distributions. These include ... 

The respirable powders of a DPI cannot be characterized adequately by single-particle studies alone bulk properties must also be assessed since they contribute to ease of manufacture and affect system performance. Primary bulk properties include particle size, particle size distribution, bulk density, and surface area. These properties, along with particle electrostatics, shape, surface morphology, etc., affect secondary bulk-powder characteristics such as powder fiow, handling, consolidation, and dispersibility. 

The sampling operation involves collection of an aerosol sample that is representative of the particle size distribution and concentration of the sampled atmosphere. The efficiency of particle transport and collection operations are dependent on the particle size, sampling velocity, the geometry of the sampling apparatus and the properties of the collection medium. In the present work, a 37 mm diameter membrane filter (0.3 ym pore size) is the primary collection medium under evaluation. The filter is housed in a standard filter cassette and effects of filter-holder inlet geometry are also being investigated. 

Pigment properties, such as particle size distribution, chemical structure, and thermal stability, as well as the process have a significant impact on the dispersion process. The primary particle diameter of the pigments is generally less than 1 tm. 

The particle size and moisture content were the two primary properties requiring a lot of pre-treatment of the samples to fit into the desired limits mentioned above. The particle size distribution was determined by normal sieving procedure. 

The major distinction between the model of La Mer and that developed for uniform latex particles lies in the incorporation of colloidal stability of small particles. The La Mer model assumes that each nucleus is colloidally stable and survives at the end of the reaction at the center of a particle. The aggregation models argue that stabilizing primary small particles is difficult, but aggregation does not necessarily result in a broad particle-size distribution. When schemes for control of particle-size distribution are developed, the result of accepting the notion that colloidal stability can play an important role is that attention is focused away from the length of the nucleation period and towards the colloidal properties of the growing particles. 

The primary route of exposure to radon and its progeny is inhalation. The degree of deposition and the subsequent absorption of inhaled radon and progeny is determined by physiological parameters, such as respiration rate and tidal volume and physical properties, such as the particle size distribution of the carrier aerosols and of the unattached fraction, the equilibrium state, and solubility coefficients (Crawford-Brown 1987 Holleman et al. 1969 Jacobi 1964). 

Dozens of reactions of free radicals (SiCla, SiClsO, Cl, OCl, H, OH, HO, =Si, =SiO, etc.), charged particles, ion-radicals, O atoms, molecules and proto-particles in the flame with SiCU, O2, H2 and related compounds on synthesis of fumed silica are worthy of special attention, since variations in synthesis conditions allow one to prepare materials strongly different in their morphological (primary and secondary particle size distributions, type of contacts between adjacent particles) and surface (concentrations of silanols and intact water) properties. These problems as well as structural and adsorptive characteristics of different silicas were analyzed in details by Mironyuk and coworkers in a series of publications [36]. 

Many physicochemical properties of fumed silica depend significantly not only on the primary and secondary particle size distributions but also on the concentration of adsorbed water (C ) in the form of intact molecules and =SiOH groups (Cqh) [1-3,6,7]. For instance, marked amounts of adsorbed water can negatively affect the characteristics of fumed silica as a filler of liophilic media or polymers. There are several methods to change C and Cqh such as chemical modification... 

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