INDEX particle shape, size

It is clearly evident that numerous mineralogies are utilised for paper filling applications however, these minerals are all classified in much the same way. Particle size and size distribution, pigment brightness, refractive index, particle shape, and specific surface area are quantifiable characteristics that can be used to predict how the pigment will perform in various paper applications. To a lesser degree, particle charge, or zeta potential, plays a role in how the filler interacts with various paper chemical additives and influences the manner in which the mineral is retained in the paper web. 

Key filler characteristics include density, particle shape, size and size distribution, surface chemistry, oil absorption capacity, hardness, and refractive index. Oil absorption is frequently measured in a few fillers such as carbon black. It is usual to measure the uptake of dibutyl phthalate under standard conditions this gives some information about the surface of the... 

Computerized techniques are sometimes employed for cost/performance evaluations. The particle shape, size and distribution, oil absorption, dispersibilty and impurities of fillers affect its performance. Use of fillers with fine particle size and a refractive index closer to PVC results in the least reduction of clarity. Surface gloss decreases with coarse types and higher loadings cause whitening. Surface treated fillers are more easily dispersed. The presence of heavy metal impurities such as iron or zinc are avoided since they cause thermal degradation of PVC. 

Source sampling of particulates requites isokinetic removal of a composite sample from the stack or vent effluent to determine representative emission rates. Samples are coUected either extractively or using an in-stack filter EPA Method 5 is representative of extractive sampling, EPA Method 17 of in-stack filtration. Other means of source sampling have been used, but they have been largely supplanted by EPA methods. Continuous in-stack monitors of opacity utilize attenuation of radiation across the effluent. Opacity measurements are affected by the particle size, shape, size distribution, refractive index, and the wavelength of the radiation (25,26). 

The PLM can be used in a reflection or a transmission mode. With either mode, light of various wavelengths from ultraviolet to infrared, polarized or unpolarized, is used to yield a wide variety of physical measurements. With just ordinary white light, a particle or any object detail down to about 0.5 p.m (500 nm) in diameter can be observed to detect shape, size, color, refractive index, melting point, and solubiUty in a group of solvents, all nondestmetively. Somewhat larger particles yield UV, visible, or IR absorption spectra. 

Suspended particles are the most important factor in visibility reduction. In most instances, the visual quality of air is controlled by partide scattering and is characterized by the extinction coeffident The size of particles plays a crucial role in their interaction with light. Other factors are the refractive index and shape of the particles, although their effect is harder to measure and is less well understood. If we could establish these properties, we could calculate the amount of light scattering and absorption. Alternatively, the extinction coeffident associated with an aerosol can be measured directly. 

In the absence of interactions, particles of differing sizes and shapes are statistically independent. For this reason, we can treat the statistical properties of light scattered from a dilute polydisperse suspension as the sum of contributions of many dilute monodisperse suspensions of particles with characteristic shape and size. Suppose that each characteristic shape/size combination is labeled with the index v. Let (V represent the number of particles having a particular shape and size. Clearly, we require N = Ns. All sums over the (V particles in a suspension can be expressed in terms of sums over the shape/size distribution. Thus we have... 

Chemical composition, particle size, particle shape, specific gravity, surface area, refractive index, brightness, absorptivity, and wettability are the most important criteria used in selecting a filler for the paper industry. For further reading, a recent monograph on the use of fillers in paper industry is an excellent source of practical information. ... 

Of particular interest are the size resolution of the counter, or its ability to distinguish between neighboring particle sizes, and the limit of detection, or smallest size to which the counter responds. The size resolution depends on the relationship between pulse height and particle size, the response cioTe, For piuticles of given optical properties, this relationship is detennined by the geometry of the illumination and light collection systems. Particle shape and refractive index also influence the relationship. 

It depends on particle size, particle shape, aspect ratio, specihc gravity of the hller, and other properties of fillers. The following example illustrates this overah property of fillers. When polypropylene, having melt flow index of 16.5 g/10 min, was fllled with some mineral and cellulosic fillers, its MFl (in g/10 min) was as follows [2] ... 

Since the scattering intensity depends additionally on refractive index and particle shape, particle sizing based on intensity measurements generally requires calibration. 

Part 2 Determination of particle size — Test sieves, nominal size of apertures Part 3 Determination of particle shape of aggregates — Flakiness index Part 4 Determination of particle shape of aggregates — Shape index... 

---