Polymerization data

There is little information on rates of initiation in coordination polymerization. With the soluble catalyst (7r-CsHs)2TiCl2—AlMejCl for ethylene, Chien [111] reported = 4.99 x 10 1 mole s at 15°C Ei = 15.5 kcal mole ). This was determined from the rate of incorporation of C14 labelled AlMe2 Cl into the polymer. In most systems examined the initiating centres have been preformed and reaction starts immediately. This is the case with Natta type catalysts from transition metal subhalides with the alkyls of aluminium, beryllium and zinc. With some catalysts the rate rises rapidly to a steady value but with others there is a rapid rise to a maximum followed by a decline to a constant rate, the latter being 

The different patterns of behaviour are shown in the polymerization of propene by VCl3/AlEt2Cl and by VClj/AlEtj (Fig. 9). In Fig. 10(a) is shown the polymerization of propene by a-TiCls/AlEts and Fig. 10(b) illustrates the dependence of the steady rate on surface area. Keii [112, 269] has studied the phenomena in the early stages of the polymerization of propene by TiCla/AlEta. Acceleration of polymerization prior to attainment of the steady rate (Fig. 10a, curve c) has been found to follow the equation 

The observation that the time to 75% of the steady rate is inversely proportional to (Rp)s [270] leads to the time dependence of i in the early stages of reaction, when t 1/fe, as (Rp )t (Rp )skt (Rp )s t. Since the steady rate is proportional to [M] it follows that the acceleration stage is second order in monomer. The activation energy for this stage was found to be 20 kcal mole .  

If allowance is made for concurrent first order catalyst decay during build-up of catalyst sites 

In the case where acceleration is followed by a declining rate from powdered TiClj (Fig. 10a, curve a) the reaction is first or second order in monomer, dependent on the order of addition of monomer and metal alkyl to the TiCl3, viz. 

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Although the results presented in Fig. 5.2 appear to verify the predictions of Eq. (5.16), this verification is not free from controversy. This controversy arises because various workers in this field employ different criteria in evaluating the success of the relationships we have presented in fitting experimental polymerization data. One school of thought maintains that an adequate kinetic description of a process must apply to the data over a large part of the time of the experiment. 

Thus both combustion and polymerization data indicate a stabilization of... 

Table 6. Polymerization Data for Acrylic Ester Monomers in Solution ...

Table 8. Polymerization Data for Methacrylic Ester Monomers ...

Certain free radical polymerization data gave curves when plotted according to Eq. (2-15) but straight lines accordingto Eq. (2-19). This apparent paradox was resolved by postulating that some constant portion R of reactant is unreactive and serves to diminish the effective reactant concentration, lowering it to Ca - / The appropriate form of Eq. (2-15) is then... 

Figure 9.8 Comparison of molecular weight distributions for a conventional and RAFT polymerization. Data shown arc GPC distributions (upper trace) for PS prepared by thermal polymerization of S at 110°C for 16 h (Mn 324000, / Mn...

The model was tested against solution polymerization data for MMA reported by Schulz and Haborth (11). The minimization of error in fitting the model to the data resulted in negative values for a. This is physically unrealistic, and suggests that the model needs modification. Further work is intended which will refine the choice of initial condition for application of the model and/or change the inverse dependency of on entanglement density to power greater than unity. 

Evaluation of F(x) for Second Order Deactivation. As mentioned earlier for the case of second order decay F(x) cannot be derived analytically, however numerical calculation of F(x) or Its evaluation from simulated rate data Indicates that the function defined In Equation 11 provides an excellent approximation. This was also confirmed by the good fit of model form 12 to simulated polymerization data with second order deactivation. Thus for second order deactivation kinetics the rate expression Is Identical to Equation 12 but with 0 replacing 02. 

Figure 9. Catalyst activity of lanthanides in diene polymerization. Data from Ref. 22.

Table III presents additional cyclopentene polymerization data with 1-pentene as a regulator at 0°C throughout a wide range of conversion. As long as the cis selectivity is maintained, the regulator remains inactive and does not participate in the scrambling process.

See also Methacrylate monomers polymerization data for, 16 279t Methacrylic ester polymers, 16 271-298. See also Methacrylate monomers Methacrylic esters analytical test methods and specifications for, 16 291-293 bulk polymerization of, 16 281-282 chemical properties of, 16 276-277 electrical properties of, 16 276 emulsion polymerization of, 16 285-288 glass transition temperature of, 16 273-274... 

Five different types of rate constants are of concern in radical chain polymerization—those for initiation, propagation, termination, chain transfer, and inhibition. The use of polymerization data under steady-state conditions allows the evaluation of only the initiation rate constant kd (or kt for thermal initiation). The ratio kp/k J2 or kp/kl can be obtained from Eq. 3-25, since Rp, Rj, and [M] are measurable. Similarly, the chain-transfer constant k /kp and the inhibition constant kz/kp can be obtained by any one of several methods discussed. However, the evaluation of the individual kp, k ktr, and kz values under steady-state conditions requires the accurate determination of the propagating radical concentration. This would allow the determination of kp from Eq. 3-22 followed by the calculation of kt, kIr, and kz from the ratios kp/ltj2, ktr/kp, and kz/kp. 

Other criteria developed to prove the existence of compensation effects (35) also favor a physical significance of compensation. Compensation has been said to be spurious if the ratio of the two extreme experimental temperatures is 0.9 and higher. Goeldi and Elias (8) polymerized methyl methacrylate in the temperature range —5° to 120°C, so that Tmin/Tmax = 268/393 = 0.68. The same reasoning applies to the polymerization data of other workers. 

M. S. Nandi and N. G. Saha Studies in chain transfer. III. Determination of chain transfer coefficients from catalysed polymerization data. J. Polymer. Sci. 14, 295 (1954). 

The free volume at which k is assumed to have reached its limiting value (henceforth called v )> as well as the value of (Vfo)m> must be determined from the emulsion polymerization data... 

A method for calculating apparent reactivity ratios based on run number theory has been applied to "starved-feed" styrene/ ethyl acrylate systems. The reactivity ratios found are in agreement with those determined from solution polymerization data. The further confirmation of the observed agreement between reactivity ratios determined at low conversions and those determined by run number theory in "starved-feed" high conversion copolymerization requires the analysis of other comonomer pairs. 

For treatment of the polymerization data for bulk 4-methylpentene-l, the integrated form of Equation 1 was used. 

The catalytic systems 4a/MMAO and 5a/MMAO are also active for propylene polymerization. The polymerization data obtained with a propylene pressure of 5 atm. at... 

When the equation for plasma polymerization [Eq. (8.2)] is applied to express the thickness growth rate of the material that deposits on the cathode cathodic polymerization), it becomes quite clear that the deposition kinetics for the cathodic polymerization is quite different. There is a clear dependence of the deposition rate on WjFM, but no universal curve could be obtained. In other words, the relationship given by Eq. (8.2) does not apply to cathodic polymerization. The best universal dependency for cathodic polymerization was found between D.R./M (not D.R./F M) and the current density IjS), where / is the discharge current and S is the area of cathode surface [5]. Figure 8.7 depicts this relationship for all cathodic polymerization data, which were obtained in the same study, covering experimental parameters such as flow rate, size of cathode, and mass of hydrocarbon monomers but at a fixed system pressure. The details of DC discharge polymerization are described in Chapter 13. 

Figure 8.7 A master eurve for the relationship between GRjM and the eurrent density for DC cathodic polymerization data obtained under various conditions for methane and n-butane, at a fixed system pressure of 50mtorr.

Fig. 1. Lower part Rate constant for thermal and y-polymerization of TS-6 as a function of conversion normalized to the rate constant at X - 0. Curves are calculated from published time-conversion curves according to K = (1 — X)- dX/dt where X is the relative polymer content. y-Polymerization data are from Ref. thermal dates represent an average of literature dates, see e.g., Upper portion vs. conversion. The dashed curve is calculated on the basis of the energy transfer...

Representative for systems exhibiting sigmoidal conversion curves Fig. 1 shows experimental results for the rate constant of the reaction of TS, evaluated from thermal and y-polymerization data according to K = (1 — X) dX(t)/dt, and normalized to the rate constant in the low conversion limit. It is obvious, that at low conversion K depends on X, contrary to what is to be expected for a simple first order reaction. The functional form of KPC) is different for the two modes of polymerization. The overall increase of K with increasing X reveals an autocatalytic reaction enhancement. A measure for its efficiency is the ratio K(X = 0.5)/K(X = 0) which tirnis out to be about 200 for TS under thermal polymerization conditions. This effect is often observed with disubstituted diacetylenes albeit with different kinetic... 

For propylene polymerizations data are given for polymer fractions insoluble in boiling ether (for TiCIj) or n-heptane (for TiCIj)... 

Formaldehyde polymerization data have also been obtained by Sauterey [48] and in the early work of Toby and Rutz [49]. More recently, Boyles and Toby [50, 51] reinvestigated the kinetics of noncatalysed gaseous formaldehyde polymerization on the basis of careful attention to the purity of the monomer formaldehyde, a study of the surface to volume ratio of the vessel and the purity of the surface on which the polymer was deposited. 

If it is assumed that / is constant for a given series, a plot of (1/DF) vs. (k U]/ Rp) should have a slope of / and an intercept of k r/kp at (ka[I]/Rp) = 0. The benzoyl peroxide-initiated polymerization data were analyzed in this manner. There was considerable experimental scatter in these plots and therefore, the data are given (Table VII) as the least squares slopes and intercepts as well as their 95% confidence limits. The average values of k r/kp, ranging from 0.8 to 1.1 X... 

Data on a thermal batch bulk polymerization at 150°C (run in a two-litre bench-scale reactor) are presented in Table III and compared with computer predictions. Here, the computer prediction of molecular weight is good (almost independent of conversion) while the predicted conversions are slightly low. Comparison of the model predictions with thermal polymerization data of Hui and Hamielec 6) and Husain and Hamielec (J7) also indicate that the... 

The bridged phospholyl-amido complexes shown in Scheme 737 have been synthesized. The compound is structurally similar to the well-known constrined-geometry Cp-amido compound (GsMe4SiMe2NBut)TiCl2, and preliminary ethylene polymerization data for the phospholyl complexes show indeed comparable catalyst activ-ities.1850... 

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