Particle size factor

Temperature has dramatic effect on the electrokinetic properties of thenno-sensitive polymers. A pH independent electrophoretic mobility of about -0.5x10 m" V s" (pH 3-11) in the presence of 0.1 mol dm NaCl was reported for synthetic poly (A-isopropylacrylamide) latex (persulfate initiator) at 20°C [17]. The same material has a mobility of about -5x10 m V s" (ten times greater ) at 50 C. This dramatic change occurs when the lowest critical solubility temperature is exceeded, and it is accompanied by substantial decrease in particle size (factor about two,... 

It should be noted that accurate temperature data may depend on a number of variables including the type of sample, mounting method, heating rate, type of melting point (equilibrium melting point vs. melt during heating) (38), as well as particle size factors. 

Several factors affect the bandshapes observed ia drifts of bulk materials, and hence the magnitude of the diffuse reflectance response. Particle size is extremely important, siace as particle size decreases, spectral bandwidths generally decrease. Therefore, it is desirable to uniformly grind the samples to particle sizes of <50 fim. Sample homogeneity is also important as is the need for dilute concentrations ia the aoaabsorbiag matrix. 

Monomer compositional drifts may also occur due to preferential solution of the styrene in the mbber phase or solution of the acrylonitrile in the aqueous phase (72). In emulsion systems, mbber particle size may also influence graft stmcture so that the number of graft chains per unit of mbber particle surface area tends to remain constant (73). Factors affecting the distribution (eg, core-sheU vs "wart-like" morphologies) of the grafted copolymer on the mbber particle surface have been studied in emulsion systems (74). Effects due to preferential solvation of the initiator by the polybutadiene have been described (75,76). 

In addition to graft copolymer attached to the mbber particle surface, the formation of styrene—acrylonitrile copolymer occluded within the mbber particle may occur. The mechanism and extent of occluded polymer formation depends on the manufacturing process. The factors affecting occlusion formation in bulk (77) and emulsion processes (78) have been described. The use of block copolymers of styrene and butadiene in bulk systems can control particle size and give rise to unusual particle morphologies (eg, coil, rod, capsule, cellular) (77). 

Adipic acid is shipped in quantities ranging from 22.7 kg (50-lb bags) to 90.9 t (200,000-lb hopper cars). Upon long standing, the soHd material tends to cake, dependent on such factors as initial particle size and moisture content. Shipping data in the United States are "Adipic Acid," DOT-ID ALT 9077, DOT Hazard Class ORM-E. It is regulated only in packages of 2.3 t (5,000 lb) or more (hopper cars and pressure-differential cars and tmcks) (157). 

Aluminum hydroxide gel may be prepared by a number of methods. The products vary widely in viscosity, particle size, and rate of solution. Such factors as degree of supersaturation, pH during precipitation, temperature, and nature and concentration of by-products present affect the physical properties of the gel. 

Particle Size Distribution. For many P/M processes, the average particle size is not necessarily a decisive factor, whereas the distribution of the particles of various sizes ia the powder mass is. The distribution curve can be irregular, show a rather regular distribution with one maximum, have more than one maximum, or be perfecdy uniform. 

Reactivity is affected by particle size. Smaller particles react faster. However, the dominant factor for reactivity is the soHdification rate. Material that is soHdified quicker reacts faster with alcohol (30). Commercial P4S q is a soHd solution containing P4S2Q, P4SC), P4Sy, free sulfur, etc (33). SoHdification rate... 

Because mass flow bins have stable flow patterns that mimic the shape of the bin, permeabihty values can be used to calculate critical, steady-state discharge rates from mass flow hoppers. Permeabihty values can also be used to calculate the time required for fine powders to settle in bins and silos. In general, permeabihty is affected by particle size and shape, ie, permeabihty decreases as particle size decreases and the better the fit between individual particles, the lower the permeabihty moisture content, ie, as moisture content increases, many materials tend to agglomerate which increases permeabihty and temperature, ie, because the permeabihty factor, K, is inversely proportional to the viscosity of the air or gas in the void spaces, heating causes the gas to become more viscous, making the sohd less permeable. 

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