Polymerization monomer balance

With as httie as 0.5% hydrolysis of the sulfone monomer, the polymerization stoichiometric balance is sufficientiy upset to prevent high molecular weight polymer from being achieved. The dependence of maximum attainable PSF molecular weight on water content during polymerization can be inferred from Figure 1. 

Severe polymerization conditions (350°C., 48 hours), in fact, gave lower molecular weight polymers ([yj] = 0.1) and a small amount of black, insoluble precipitate. These results suggest that there was considerable degradation which interfered with monomer balance. Such... 

From the material balance for the more rapidly polymerizing monomer he derived a differential equation ([M,] + [M2] = M)... 

Interval III is characterized by polymerization in a constant number of latex particles in the absence of monomer droplets. The concentration of monomer in the latex particles thus declines as polymerization progresses. The principal modification required for the application ofEq. (S) in modeling Interval III is its coupling with a monomer balance equation and the modification of the growth factor K to incorporate the declining monomer concentration. A full monomer balance equation for a batch reactor demands the consideration of the monomer consumed in both the aqueous phase and the particles iMin and Ray, 1974). Frequently, however, the aqueous phase consumption is relatively small so that only consumption in the latex phase is significant. The latter is given by... 

Other materials balance equations may be coupled with Eq. (5) in an way analogous to the monomer balance equation. This is necessary if the availability of some species changes significantly with time, e.g., when the initiator has a half-life comparable to (or shorter than) the polymerization half-life. 

To achieve this balance between rate and MW, rates of polymerization (monomer consumption rates) at low conversion are of order 10 -10 mol s such that approximately 10 -10 s is required to take a batch system to complete conversion. Faster rates can be achieved by increasing Pinit. but at the expense of decreased polymer MW. 

Polymerization can occur under non-equilibrium conditions, thus eliminating the critical dependency on the monomer balance (typical of high-... 

Volume contraction due to the difference in polymer and monomer densities can be as high as 20% for bulk polymerization, and should not be neglected when solving the material balances. Solution of the initiator balance and substitution into the monomer balance lead to a differential equation for conversion, Eq. (91), where the volume contraction factor is deflned as s = pjinai Pa) /Pfind where is the... 

Integration of Equations 16.26-16.29 along with the monomer balance will describe the monomer conversion and molecular weight distribution as a function of time for the batch anionic polymerization. Addition of the enthalpy balance will allow the simulation to be done nonisothermally. 

It is generally accepted that the number of latex particles per unit volume of water, the average number of free radicals per particle (n = 0.5), and the concentration of monomer in the particles are constant for emulsion polymerization systems that follow the ideal Smith-Ewart Case 2 kinetics. As a result, a constant reaction rate period can be observed during emulsion polymerization. Monomer molecules must be transferred from the gigantic monomer droplets to the growing submicron latex particles to supply the reaction. A dynamic balance between the rate of consumption of monomer in the latex particles and the rate of diffusion of monomer molecules from the monomer droplets to the particles may thus be established, and this results... 

For a fixed extent of reaction, the presence of multifunctional monomers in an equimolar mixture of reactive groups increases the degree of polymerization. Conversely, for the same mixture a lesser extent of reaction is needed to reach a specified with multifunctional reactants than without them. Remember that this entire approach is developed for the case of stoichiometric balance. If the numbers of functional groups are unequal, this effect works in opposition to the multifunctional groups. 

Basic Components. The principal components in emulsion polymerization are deionized water, monomer, initiator, emulsifier, buffer, and chain-transfer agent. A typical formula consists of 20—60% monomer, 2—10 wt % emulsifier on monomer, 0.1—1.0 wt % initiator on monomer, 0.1—1.0 wt % chain-transfer agent on monomer, various small amounts of buffers and bacteria control agents, and the balance deionized water. 

In general, rubber manufacturers balance thiol reactivity and odor. The stmcture of the thiol plays a significant role in its abiUty to be transported within the polymer matrix, particularly in emulsion polymerizations, ie, mixed water—monomer emulsion. The odor of light thiols is generally too strong for most mbber manufacturers, as it is generally hard to remove residual odors from polymers. 

Partially hydrolyzed poly(vinyl alcohol) grades are preferred because they have a hydrophobic /hydrophilic balance that make them uniquely suited for emulsion polymerization. The compatibUity of the residual acetate units with the poly(vinyl acetate) latex particles partly explains the observed stabilization effect. The amount of PVA employed is normally 4—10% on the weight of vinyl acetate monomer. The viscosity of the resulting latex increases with increasing molecular weight and decreasing hydrolysis of the PVA (318). 

The earliest study describing vulcanised polymers of esters of acryUc acid was carried out in Germany by Rohm (2) before World War I. The first commercial acryUc elastomers were produced in the United States in the 1940s (3—5). They were homopolymers and copolymers of ethyl acrylate and other alkyl acrylates, with a preference for poly(ethyl acrylate) [9003-32-17, due to its superior balance of properties. The main drawback of these products was the vulcanisation. The fully saturated chemical stmcture of the polymeric backbone in fact is inactive toward the classical accelerators and curing systems. As a consequence they requited the use of aggressive and not versatile compounds such as strong bases, eg, sodium metasiUcate pentahydrate. To overcome this limitation, monomers containing a reactive moiety were incorporated in the polymer backbone by copolymerisation with the usual alkyl acrylates. 

It may also be possible to crosslink the acrylic PSA with the help of multifunctional acrylates or methacrylates [87], These monomers can simply be copolymerized with the balance of the other monomers to form a covalently crosslinked network in one step. Since the resulting polymer is no longer soluble, this typ)e of crosslinking is typically limited to bulk reactions carried out as an adhesive coating directly on the article or in emulsion polymerizations where the crosslinked particles can be dried to a PSA film. 

Mixtures of monomers can be used to balance properties. This is possible due to the ease of copolymer formation via free-radical polymerization. The glass transition temperature of acrylic copolymers can be predicted from the weight fraction of the component monomers and the glass transition temperatures of the respective homopolymers [20]. Eq. 3 (commonly known as the Fox equation) is reported ... 

Polymerization inhibitors are key additives which prevent premature gelation of the adhesive. The foimulator must carefully balance shelf stability and the required cure on demand. Due to its high propagation rate, MMA is difficult to inhibit. Some comments on specific inhibitors follow. The most common inhibitor to be found in component monomers is 4-methoxyphenol, which is also called the methyl ether of hydroquinone. This inhibitor is effective only in the presence of oxygen. A mechanism has been proposed, and is illustrated in Scheme 13 [128]. 

A VCM (vinyl chloride monomer) production unit uses three vertically mounted agitated reactors for the polymerization of vinyl chloride. Crude material balances infer about 8 to 10% monomer losses. Describe how you would go about assessing whether these losses are due to leaks such as fugitive air emissions. Be specific in recommending procedures and instruments. 

Several components of the organic phase contribute greatly to the character of the final product. The pore size of the gel is chiefly determined by the amount and type of the nonsolvent used. Dodecane, dodecanol, isoamyl alcohol, and odorless paint thinner have all been used successfully as nonsolvents for the polymerization of a GPC/SEC gel. Surfactants are also very important because they balance the surface tension and interfacial tension of the monomer droplets. They allow the initiator molecules to diffuse in and out of the droplets. For this reason a small amount of surfactant is crucial. Normally the amount of surfactant in the formula should be from 0.1 to 1.0 weight percent of the monomers, as large amounts tend to emulsify and produce particles less than 1 yam in size. 

The performance of secondary alkanesulfonates in applications as emulsifiers in the widespread emulsion polymerization of vinyl monomers can be assessed by their hydrophilic-lipophilic balance (HLB) numbers. The HLB numbers can... 

This paper presents the physical mechanism and the structure of a comprehensive dynamic Emulsion Polymerization Model (EPM). EPM combines the theory of coagulative nucleation of homogeneously nucleated precursors with detailed species material and energy balances to calculate the time evolution of the concentration, size, and colloidal characteristics of latex particles, the monomer conversions, the copolymer composition, and molecular weight in an emulsion system. The capabilities of EPM are demonstrated by comparisons of its predictions with experimental data from the literature covering styrene and styrene/methyl methacrylate polymerizations. EPM can successfully simulate continuous and batch reactors over a wide range of initiator and added surfactant concentrations. 

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