Particle Size Distribution PSD

The particle size distribution (PSD) can have a fundamental effect on the physical properties of dispersions that are common polymer products. The measurement of just the average particle size may not be sufficient. For example, the presence of populations of different sizes resulting in a multimodal distribution could have a strong influence on final properties and may need to be controlled. 

There are several particle size measurement techniques in use, such as optical imaging, electron imaging, optical diffraction and scattering, electrical resistance changes, sieving, sedimentation, and ultrasonic attenuation [4j. 

Optical (larger than 1 pm) and scanning electron microscopy (SEM) techniques literally give the clearest picture of a PSD. However, analyzing the images may be tedious without image analyzers. Nevertheless, this method can be used as a check or calibration on the indirect methods. 

The Coulter-counter particle size analyzer (larger than 0.5 pm) is used for measuring volumes of individual particles. Particles are suspended in a conductive fluid, into which electrodes are placed. As a particle passes through an aperture between the electrodes, it displaces its own volume of electrolyte, and there is a measurable change in the electrical resistance of the system. The change becomes a precise measure of particle volume. These volumes can then be put into size bins and the PSD can be constructed. 

Turbidimetry has been used traditionally in industry to obtain a measure of average particle size and even the entire PSD, and is a measure of the attenuation of a beam of light passing through a suspended particle sample [8]. 

---

The particle size distribution (PSD), sodium (Na), rare earth (RF), and surface area (SA) are some of the parameters in the inspection sheet that require close attention. 

Table 1 shows that catalysts prepared on the same type of support have about the same particle size distribution (PSD). Table 1 also shows that the newly developed CPS4 supported catalysts have the smallest span of particle size distribution, therefore, it has the fastest filtration rate. Filtration rate is measured by measuring the filtration time of 350 ml of 4-benzyloxyphenol debenzylation products. 

Research on the modelling, optimization and control of emulsion polymerization (latex) reactors and processes has been expanding rapidly as the chemistry and physics of these systems become better understood, and as the demand for new and improved latex products increases. The objectives are usually to optimize production rates and/or to control product quality variables such as polymer particle size distribution (PSD), particle morphology, copolymer composition, molecular weights (MW s), long chain branching (LCB), crosslinking frequency and gel content. 

The importance of chemical-reaction kinetics and the interaction of the latter with transport phenomena is the central theme of the contribution of Fox from Iowa State University. The chapter combines the clarity of a tutorial with the presentation of very recent results. Starting from simple chemistry and singlephase flow the reader is lead towards complex chemistry and two-phase flow. The issue of SGS modeling discussed already in Chapter 2 is now discussed with respect to the concentration fields. A detailed presentation of the joint Probability Density Function (PDF) method is given. The latter allows to account for the interaction between chemistry and physics. Results on impinging jet reactors are shown. When dealing with particulate systems a particle size distribution (PSD) and corresponding population balance equations are intro-... 

These relations can be spread to the systems of particles of one form, but of various sizes, D. The specific surface area of such PS is equal to the sum of surface areas of particles related to the entire mass. At known particle size distribution (PSD), v(D), one has... 

Figure 9.26 The scheme of the simple interrelation of pore size distributions (psd), particle size distributions (PSD), and particles space arrangement (PSA).

Using the catalyst vendor s equilibrium catalyst report, the physical properties of the circulating catalyst may be monitored for any change. Albemarle routinely analyzes a sample of the circulating catalyst inventory among others for physical characteristics, including surface area (SA), metal content, apparent bulk density (ABD), and particle size distribution (PSD). 

Particle size distributions (PSD) measurement of dispersion of metal particles on supports... 

The morphology and the calculated particle size distribution (PSD) of TiO (ST) particles are shown in Fig. 1.3 (a) and (b). It was observed that the PSD is between 10 and 33 nm with a mean diameter of 17 -19 nm, which is somewhat larger than the one determined from XRD. However, SEM does not allow us to see the smallest particles and particles that look like single crystals in SEM may indeed be twinned or polyaystal-Une. Thus, we expect SEM analysis to give overestimated values of the particle size. 

In addition to the patent literature available on the production of BR in the gas-phase there is some scientific literature which mainly refers to the modeling of reaction kinetics. Details on the experimental procedure for the determination of the macroscopic kinetics of the Nd-mediated gas-phase polymerization of BD in a stirred-tank reactor are reported [568,569]. Special emphasis is given to video microscopy of individual supported catalyst particles, individual particle growth and particle size distribution (PSD). These studies reveal that individual particles differ in polymerization activity [536,537,570,571]. Reactor performance and PSD are modeled on the... 

While the simple process of comparing fractograms with appended particle diameter scales will provide all the information needed in many particle characterization studies, the fractogram does not constitute a finished particle size distribution (PSD) curve. To obtain a quantitative PSD curve, corrections must be applied. The first correction, which we call a scale correction, is necessary because elution volume and particle diameter are not proportional to one another. Thus the particle content of a fixed volume of eluted sample will correspond to a different increment in d depending upon the point of collection. A simple correction factor, detailed elsewhere (3), can be applied to this scale problem. 

Particle size distribution as well as an average particle size can be determined by HDC. One of the main limitations to an accurage determination of the particle size distribution (PSD) as well as to the range of applicability of HDC is the low mass recovery due to capture of particles bigger than 200 nm. Silebi and McHugh (5), in their analysis of the determination of particle size distribution by HDC, concluded that size distributions could be calculated accurately only for systems with particle sizes below about 300 nm due to poor recovery of larger particles. 

---