Polymerization rate comparison

The styrene conversion versus reaction time results for runs in the laminar flow regime are plotted in Figure 8. Both the rate of polymerization and the styrene conversion increase with increasing flow rate as noted previously (7). The conversion profile for the batch experimental run (B-3) is presented as a dashed line for comparison. It can be seen that the polymerization rates for runs with (Nj e e 2850 are greater than the corresponding batch polymerization with a conversion plateau being reached after about thirty minutes of reaction. This behavior is similar to the results obtained in a closed loop tubular reactor (7J) and is probably due to an excessively rapid consumption of initiator in a... 

Indeed, reaction (20) can be considered as a real chain transfer with the monomer. In fact, by making a comparison between the reactions (20) and (6) and (7), it can be observed that, after these reactions, the catalytic complexes [CatJCHaCHaCHs and [CatJCHaCHa are respectively formed and both these complexes can add monomeric units in the polymerization process. The reactions (6) and (7) are equivalent to a real chain transfer because the over-all polymerization rate appears to be independent of the triethylaluminum concentration. Considering the chemical analogies of the catalytic complexes, resulting from the reactions (20) and (7), it may also be assumed that the transfer reaction whose rate is of first order with regard to the monomer may be considered a real chain transfer (from a kinetic point of view). 

The monomer 1 was polymerized by heating the crystals in a vacuum vessel below the melting point or by y-ray or UV irradiation of the crystals at room temperature. 60Co y-ray irradiation with a dose rate of 0.1 Mrad h 1 or a high-pressure mercury lamp (200 W) without filter was used as the radiation sources for the polymerization the conversion ratio was determined by extraction of residual monomer with ethanol. A comparison of the polymerization rates indicates that 60C y-ray irradiation is much more efficient than UV irradiation in inducing polymerization. 

The photopolymerization of the polymers studied is influenced by the sensitizer as well as the intensity of light used. Aromatic hydrocarbons, like anthracene and tetracene, are used as singlet sensitizers whereas 1-chlorothioxanthone (CTX) is a triplet sensitizer. From the comparison of the polymerization rates of the systems studied as a function of sensitizer it follows that there is a dependence on the type of sensitizer. As seen from Fig. 2, CTX as triplet sensitizer has been found to be the best sensitizer for vinyl ether systems. 

TABLE I. COMPARISON f riSRCENT CONVERSION AT CMC BY CONDUCTIVITY ruiftSaREMENTS AND POLYMERIZATION RATES... 

TABLE II. COMPARISON OF PARTICLE DIAMETERS FROM POLYMERIZATION RATE ANALYSIS WITH MEASUREMENTS BY ELECTRON MICROSCOPY... 

Figure 3. Comparison of the dependency of polymerization rate on surfactant concentration of the standard styrene and styrene/Nujol (1 0.25) emulsion systems...

The existence of a further type of active centers was demonstrated by Pino and Rotzinger93> by polymerizing ethylene with a MgQ2-supported catalyst in the presence of an electron donor. A comparison of the ethylene and propylene kinetic curves shows that, while propylene polymerization is characterized by the well known rapid decrease in rate, the ethylene polymerization rate increases reaching a constant value after about 30 min. This has been attributed to the existence of active... 

Figure 22 includes the temperature dependent polymerization rates (1), (2) and (3). The thermal polymerization kinetics (1), they — (2), and the UV photopolymerization kinetics (3) have been investigated by the method of diffuse reflection spectroscopy and other methods The activation energy of the thermal reactions (2) and (3) following the photoinduced dimerization processes, (150 + 30) meV, is appreciable lower than those of the dimer DR intermediates. However, the processes which dominate the polymerization reaction are determined not by the short diradicals with n 6 but by the long chains with n 7, which all have a carbenoid DC or AC structure. The discrepancy of the activation energies therefore may be due to the different reactivities of the diradical and carbenoid chain ends. The activation energies of the thermal addition reactions of the AC and DC intermediates at low temperatures have not been determined and therefore a direct comparison with those of the diradicals is not possible. 

As can be seen from Fig. 7, variation of the initial emulsifier concentration from 0-5 to 5% in the aqueous phase results in an increase in the BMA polymerization rate (conversion after 30 min) by about 15 times, whereas the MA polymerization rate essentially does not change with changing emulsifier concentration. The data in Table IV show how emulsifier concentration affects particle size and, accordingly, number. Although for both monomers an increase in the emulsifier concentration results in a decrease in the size and an increase in the number of particles, the effect is much weaker in the case of MA polymerization. A comparison of run 2 with runs 3,4, and 5 in Table IV indicates that at the same initial emulsifier concentration the number of particles in 1 dm of the latex is an... 

Fig. 3. Polymerization rate Theory—experimeni comparisons (Poehlein and De Graff, 1971)...

A comparison of the 7 form of TiCl3 with the a and (3 forms gave the following polymerization rates at 80°C. 

Temperature Effect. The experiments concerning temperature effects are carried out between — 80°C. and -b60°C. in the presence of a 5 A. LMS. Comparison of various experiments with constant ethylene and solid quantity submitted to equal amounts of gamma energy, at temperatures beyond 9°C. which is the critical ethylene temperature, shows the polymerization rate to decrease with increasing temperature. Below 9°C. down to — 80°C., the polymerization rate varies slowly and seems to be slightly affected by temperature. 

HEMA) [212]). Monomer 42 (MFC) spontaneously polymerizes at room temperature in aqueous solution and the choice of the slowest catalyst is therefore justified. Because poly-38 [212] is not soluble in water, the polymerization is run in a 50 50 MeOH water mixture. Consequently, rates are lower than in water (95% conversion requires 3-4 h reaction time at room temperature). A comparison of polymerization rates in aqueous and non-aqueous media reveals strong solvent effects. Polar solvents have been found to increase the polymerization rate, possibly because of the combined effect of an increase of rate constant [213] and a competitive coordination of the solvent and the ligand in the copper species [214]. 

Comparison of Eq. (P6.8.11) with Eq. (6.26) shows that the polymerization rate... 

Figure 168 is also a plot of two other moments of the instantaneous rate, and for comparison Figure 169 shows a plot of these same moments for a typical Cr/silica-titania-catalyzed polymerization. The instantaneous rate is shown, that is the polymerization rate at any given time when the ethylene concentration in the reactor is held constant. Another moment, the polymer yield, is just the integral of the rate curve up to that point in... 

Figure 2. Comparison of surface vs. bulk polymerization rates. Key , FTIR — PAS/air and O. FTIR.

Comparison of Polymer 16 polymerization (control) with 17 shows essentially identical polymerization rates up to the point of shortstop addition after 8 minutes of polymerization time. In Polymer 16 we see the polymerization begin to slow down after about 8 minutes of reaction at 420 meter-grams but to achieve 490 meter-grams in 10 minutes without die-out. 

Figure 6.11 Comparison of conversion-time plots for normal, inhibited, and retarded free-radical polymerization. Curve 1 normal polymerization in the absence of inhibitor/retarder. Curve 2 inhibition polymerization is completely stopped by inhibitor during the initial induction period, but at the end of this period with the inhibitor having been completely consumed, polymerization proceeds at the same rate as in normal polymerization (curve 1). Curve 3 retardation a retarder reduces the polymerization rate without showing an induction period. Curve 4 inhibition followed by retardation (After Ghosh, 1990).

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