Power feed polymerization

The modulus in this case is the secant modulus at 1% strain. Both polymers had the same composition 39/59/2 - methyl methacrylate/ butyl acrylate/acrylic acid. The power feed example was prepared such that butyl acrylate varied 0.83 — 0.30 and methyl methacrylate varied 0.15 — 0.68 as the polymerization proceeded, with x = 0.83. While both examples show the usual trend of high modulus at low temperature to low modulus at higher temperature, the power feed polymer exhibits a much broader transition region than the uniform example. 

The toughness parameter q is defined by Equation 13. The effect of nonuniform polymerization is shown for a 50/50 copolymer in which the power feed profile involved a decreasing ethyl acrylate concentration (0 1), with x = 1 (linear). (( ) power feed, q = 0.19)... 

The "onion skin" growth mechanism is supported by filming experiments in which film formation is greatly effected by the nature of the monomer composition added last in the polymerization. In power feed examples, as well as in staged feeds, hard and hydrophobic compositions hinder film formation while softer and more hydrophilic compositions aid film formation. Curiously, in this respect, it was found that the filming characteristics of all-acrylic latexes responded to non-uniform polymerization techniques much more dramatically than did their styrene-acrylic counterparts. 

Figure 13. The effect of nonuniform polymerization on the expansion behavior of carboxylic emulsion polymers. The power feed example was prepared using the monomer feed profile illustrated in Figure 12 ((%) uniform feed power feed).

In order to design experiments to test the influence of process variables on polymer infrastructure, a simple but general process design is needed. For these studies a new sequential feed polymerization process called "power-feed" was chosen (7 -8, 9). The advantage of this technique is that almost any conventional monomer feed profile can be simulated and described by an equation containing only three independent variables. In addition, a number of novel monomer composition profiles can also be constructed with this approach. The composition of the monomer feed to the reactor can be described by ... 

The latexes were prepared using a conventional semi-batch emulsion polymerization system modified for power-feed by the addition of a second monomer tank. Polymerization temperatures ranged from 30-85°C using either redox or thermal initiators. Samples were taken periodically during the polymerization and analyzed to determine residual monomer in order to assure a "starved-feed" condition. As used in this study this is a condition in which monomer feed rate and polymerization rate are identical and residual monomer levels are less than 5%. 

Figures 2, 3 and 4 illustrate the differences between conventional mixed feed, staged and power-feed copolymers whose average composition is 50/50 ethyl acrylate/styrene. In the case of the staged polymerization, all the ethyl acrylate was fed first followed by the styrene. The power-feed copolymer was prepared with ethyl acrylate linearly increasing as a function of time, i.e., x = 1.0, = 0.

The differences in the three polymerization processes are immediately apparent in the spectra. For the conventional copolymer, Figure 2, there is a predominance of BAB triads (EA = A). The power-feed copolymer appears to have relatively higher concentrations of mixed (AAB = BAA) and homo (AAA) triads. In the case of the stage polymerization, Figure 3, the carbonyl resonance is essentially identical to that for poly(ethyl acrylate), that is, AAA triads. 

Guyot et a/. have described a so-called corrected-batch process for producing copolymers of constant composition by emulsion polymerization. Unlike the power-feed process, the polymerization is carried out in the presence of excess monomer. The principle is to monitor the composition of the unreacted monomer by gas-liquid chromatography, and then to use this information to correct for difference in the rates of copolymerization of the two monomers by controlling the relative rates of feed of the two monomers to the reactor. The objective is to keep the monomer-feed composition constant, and hence also the composition of the copolymer which is being produced instantaneously. 

Acyclic C5. The C5 petroleum feed stream consists mainly of isoprene which is used to produce rubber. In a separate stream the linear C5 diolefin, piperylene (trans and cis), is isolated. Piperylene is the primary monomer in what are commonly termed simply C5 resins. Small amounts of other monomers such as isoprene and methyl-2-butene are also present. The latter serves as a chain terminator added to control molecular weight. Polymerization is cationic using Friedel-Crafts chemistry. Because most of the monomers are diolefins, residual backbone unsaturation is present, which can lead to some crosslinking and cyclization. Primarily, however, these are linear acyclic materials. Acyclic C5 resins are sometimes referred to as synthetic polyterpenes , because of their similar polarity. However, the cyclic structures within polyterpenes provide them with better solvency power and thus a broader range of compatibility than acyclic C5s. 

The power exponent, x determines what the monomer feed profile will look like as a function of of. Some examples of more common feed profiles are shown in Figure 1. If the polymerization is carried out under monomer-starved conditions, the composition of the polymer being formed at any instant is the same as the feed composition, C-. Therefore, the cumulative polymer composition at any timeef may be obtained from ... 

As the power input is increased (at a given flow rate), the domain of plasma polymerization approaches the monomer-deficient one, which can be recognized by the asymptotical approach of D.R. value to a horizontal line as the power input increases. In the monomer-deficient domain, the deposition rate (plateau value) increases as the flow rate is increased and shows a linear dependence on the monomer feed-in rate at a given discharge power and the system pressure (Fig. 8.2), i.e.,... 

This process takes place in an electrically-heated bed of coke particles at 1300—1600°C [20]. In order for the process to be economical, cheap and abundant power is required [21]. The advantages of the Shawinigan process are 1) hydrogen can be recycled to the ammonia feed unit, 2) there is no need for ammonia absorption facilities, and 3) the absence of water vapor and low concentration of ammonia suppresses undesirable polymerization [22], This process is currently used in a commercial plant in South Africa [23]. Other processes involved in the formation of hydrogen cyanide include ... 

A CSTR is commonly used for the bulk polymerization of styrene. Assume a mean residence time of 2 h, cold monomer feed (300 K), adiabatic operation (UA i = 0), and a pseudo-first-order reaction with rate constant k = 10 ° exp(—10000/T) h where T is in kelvin. The adiabatic temperature rise for complete conversion is approximately 400 K. Assume constant physical properties and ignore power input form the agitator. 

A 240 mm 3-core polymeric insulated cable 25 km in length feeds a static load of 20 MVA at a power factor of 0.95 lagging. The nominal system voltage is 33,000 V and the sending end voltage... 

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