Suspension polymerization relationship

NIR and Raman Suspension and emulsion polymerization [126-128] Non-invasive/Average particle size only, calibration required, system specific, chemometric required Emulsion and suspension polymerization. Relationship between spectra and particle size, not clear. No industrial applications. 

Factors which influence the particle size formed during suspension polymerization are the ratio of monomer to water, the viscosity of the aqueous medium as modified by suspending agents or protective colloids, the rate of agitation, the diameter and shape of the reaction vessel, and the relationship of agitation rate to agitator shape and diameter, to mention only a few [116]. 

Pol5mierization conditions of suspension polymerization affect porosity. These aspeets of polymerization are well studied and the available results permit us to outline existing relationships. 

Emulsion polymerization is superficially related to suspension polymerization, but the kinetic relationships are entirely different. The major causes of the differences are first, the monomer droplets in the latter system are approximately 0.1-1 mm in size and the particles in the former are approximately 10 to 10" mm in size and second, the catalyst is dissolved in the aqueous phase in the latter but is incorporated directly into the droplets in the former. 

Table XII gives the half-lives of several initiators which are of interest in suspension polymerizations of vinyl chloride. While these data are a rough guide to the temperature-time relationship to be expected, many other factors need to be considered. For example, lauroyl peroxide brings about a polymerization process of vinyl chloride in which the maximum rate takes place between 60% and 80 o conversion whereas the rate of polymerization with diisopropyl peroxydicarbonate is much more uniform throughout the process. Also, particle structure varies with the initiator used [139]. The development of initiators has been in the direction of molecules with unsymmetrical substitution about the peroxide bridge. Data on these compounds are also included in Table XII [139, 140].

When all the monomers in a suspension polymerization are virtually immiscible with the continuous phase, then the instantaneous copolymer composition can be predicted from idealized relationships which apply to homogeneous systems. However, the use of those relationships is not straightforward if one, or more, of the monomers is partially soluble in the continuous phase, because the actual composition of the drops may then be unknown. The effective monomer concentrations. 

In the suspension polymerization of vinyl chloride, Zeifa and Brooks found the relationship in Eq. (8). 

Relationship of Limiting Viscosity Number to the Tenq)erature of Polymerization for Suspension PVC. 

The foregoing relationships of chain length to extent of reaction would then be expected to apply to such step polymerizations as are involved in the synthesis of poly(alkylene sulfides) from a dihalide and sodium polysulfide (polycondensation) or in the formation of the urethane polymers from glycols and diisocyanates (polyaddition). The polysulfide reaction is actually carried out in a suspension of the dihalide in an aqueous solution of the polysulfide, using a surfactant to stabilize the resulting polymer suspension. 

The adhesion of suspended particles to vessel walls likewise depends on the temperature of the liquid medium. This relationship, in the case of polymeric particles forming a suspension with a concentration of 15%, was found to be as follows [191] ... 

A few distributions of VCM suspensions in water viewed by light microscopy into specially designed pressure cells appear in the literature (23,24), but no analyses of droplet size distribution under different conditions of reactor agitation or polymeric additive addition have been reported. A technique for fixing VCM emulsions by osmium tetroxide (25) may prove useful to study the VCM/water system in greater detail. Mersmann and Grossmann (26) have studied the dispersion of liquids in non-miscible two-phase systems, which include chlorinated liquids such as carbon tetrachloride in water. The influence of stirrer type and speed on the development of an equilibrium droplet size distribution is discussed. Different empirical relationships to calculate the Sauter mean diameter of droplet distributions from reactor operating parameters are also reviewed. 

In Section 3.1 we define two basic flows used in the characterization of polymeric fluids along with the appropriate material functions. These basic flows are also found in polymer processes. In Section 3.2 several constitutive equations capable of describing the viscoelastic behavior of polymer melts are presented. The emphasis in this section is on manipulating these equations for flows in which the deformation history is known. In this section we have added discussion of fiber suspensions as they are commonly processed to yield materials with increased stiffness and strength. In Section 3.3 an introduction into the methods for measuring rheological properties is presented. In Section 3.4 several useful relationships between material functions are presented. These relationships (or correlations) are important as they allow one to obtain estimates, for example, of steady shear material functions from linear viscoelastic data. Because... 

Professor Cohen received an Excellence in Teaching Award for his course on polymeric materials based on this textbook. His research interests focus on the structure-property relationships of elastomers and the testing of theories of rubber elasticity and fracture. Previous research efforts were devoted to the study of suspensions and their applications. He was a co-principal investigator of the Cornell Injection Molding Program initiated under a grant from the National Science Foundation (NSF) and supported by an industrial consortium until 2000. 

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