Conversion molecular weight

The transfer constant governs the number of propagation steps per activation cycle and should be small for a narrow molecular weight distribution. Rearrangement of eq. 17 to eq. 18 suggests a method of estimating transfer constants on the basis of measurements of the conversion, molecular weight and dispersity.2j... 

In order to estimate the dependence of the termination rate constant on conversion, molecular weight and temperature, the following is assumed k- becomes diffusion controlled when the diffusion coefficient for a polymer radical Dp becomes less than or equal to a critical diffusion coefficient D ... 

Hamielec and coworkers (, 42, 43) have conducted extensive experimental and theoretical studies with styrene polymerization in CSTR s. Theirs represent probably the first published work in this area at commercially interesting temperatures and conversions relating theory to experiment, and determining the effects of reactor configuration and conditions on conversion, molecular weight and MWD. 

The study of the peak temperature sensitivity to the reactor operating parameters and the construction of sensitivity boundary curves for stable reactor operation were previously reported ( l). This paper presents a computer study on conceptual relationships between the conversion-product properties and the reactor operating parameters in a plug flow tubular reactor of free radical polymerization. In particular, a contour map of conversion-molecular weight relationships in a reactor of fixed size is presented and the sensitivity of its relationship to the choice of initiator system, solvent system and heat transfer system are discussed. 

This work particularly emphasizes the importance of selecting the initiator system for optimum reactor operation and reveals general concepts which specify the desired properties and operational modes of an optimum initiator system. In addition, the effects of the system heat transfer and the CTA (chain transfer agent) level on the conversion-molecular weights relationships are presented. 

Equation (8) provides a general relationship between the reactor temperature profile and the operating parameters. In relating the system heat transfer to the conversion-molecular weights relationship for a reactor of fixed size, the heat transfer coefficient emerges as the correlating parameter. 

Therefore, livingness is validated by analyzing the linear conversion-time, conversion-molecular weight and conversion-iniferter concentration relationships. However, such an interpretation appears to be too simple to describe the whole process of iniferter-based radical polymerization, which is far more complex than expected. 

At each temperature, the expected rapid rise of complex viscosity with conversion, molecular weight build-up, and ultimate solidification was observed and the complex... 

The cloud point curves of the epoxy monomer/PEI blend and BPACY monomer/PEI blend exhibited an upper critical solution temperature (UCST) behavior, whereas partially cured epoxy/PEI blend and BPACY/PEI blend showed bimodal UCST curves with two critical compositions, ft is attributed to the fact that, at lower conversion, thermoset resin has a bimodal distribution of molecular weight in which unreacted thermoset monomer and partially reacted thermoset dimer or trimer exist simultaneously. The rubber/epoxy systems that shows bimodal UCST behavior have been reported in previous papers [40,46]. Figure 3.7 shows the cloud point curve of epoxy/PEI system. With the increase in conversion (molecular weight) of epoxy resin, the bimodal UCST curve shifts to higher temperature region. 

About 25 years ago, F. T. Wall proposed such a method, which depended on the measurement of the so-called partial conversion molecular weight (I). If N is the number of polymeric molecules and W the weight of polymer, then the number average molecular weight Mn is given by W/N, from which it is easy to show... 

It should be stressed, however, that at present practically no experimental data on network formation (critical conversions, molecular weights, sol fractions, etc.) in these systems are available. 

Incidentally, as a matter of speculation, if one assumes that 0.025 to 0.04 mole % of formic acid were present in the original formaldehyde solution one could expect polymerization results of the uncatalysed polymerization in terms of conversion, molecular weight and rate similar to the ones Fukui et al. [36] reported. 

The relevant variables to be monitored in emulsion polymerization are temperature, flow rate, conversion, molecular weight, particle size, density, viscosity. 

To determine the effects of monomer feed ratio on conversion, molecular weight and structure of copolymer, various feed ratios (1 4, 1 2, 1 1, 2 1 and 4 1) of MA-ID were examined (Table IV). Conversions were 37, 62, 71, 51 and 25%, respectively. Assuming only 1 1 copolymer produced, the corresponding conversions are 98, 96, 71, 72 and 60%. The composition of the copolymers tends to be independent of the monomer feed ratios. These facts are coincident with the alternative structures of the resultant copolymers. Molecular weights also tend to be independent of feed ratios, with comparable low molecular weights obtained for all feed ratios. 

High conversion. Molecular weights and molecular-weight distributions at high conversions are less predictable and more dependent on the nature of the monomer. The two principal additional factors that come into play are chain transfer to polymer and the decrease of the rate coefficients for coupling and disproportionation with increasing polymer content, viscosity, and chain entanglement. 

Thus, just as with the IB systems, the polymerization experiments with St included the investigation of the effect of time, temperature, electron donor concentration ([ED]), solvent polarity, Friedel-Crafts acid concentration ([MtX ]), and aging on polymerization rate (conversion), molecular weight, and molecular weight distribution. The experimental conditions together with the raw data are shown in Tables 12-19 in the Appendix. 

Table IV presents the results of the ATRP of styrene in bulk using various initiators with attached functional groups (77). After a fbmd period of time, the polyrnerization reactions were stopped and conversion, molecular weight and polydispersity were measured. In ne y all cases, polymers with molecular weights predetermined by the ratio of concentration of reacted monomer to introduced initiator were obtained. The polydispersities were generally low. Only when allyl-2-chloro-...

Polymerization Temp m Initiators Time (hr) Conversion (%) Molecular Weights Ref. 

Solvent Temperature Reagent concentrations % Conversion Molecular weight range M /M ... 

Serra and coworkers studied the outstanding effect of mixing on conversion, molecular weight and polydispersity in free-radical polymerizations of styrene by a numerical simulation using different micromixer geometries [170, 171]. 

Fig. 2. Polymerization of styrene with the AlEtjCl/RCl initiator system (24). Dependence of conversion, molecular weight (M , and M ), and molecular weight dispersity (MJM ) on coinitiator concentration...

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