Monomer continued weight fraction

Continuous Stirred Tank Reactors. Biesenberger (8) solved for the MWD with condensation polymerization in a CSTR, analogous to the treatment Denbigh (14) provided for the other two mechanisms. In this case, the variable residence time distribution leads to an extremely broad MWD with even the maximum weight fraction at the lowest molecular weight (monomer). The dispersion index approaches infinity as the condensation is driven to completion in a stirred tank reactor. A sequential analytical solution of the algebraic equations was obtained with a numerical evaluation of the consecutive equations. 

The effect of the monomer concentration in the dispersed phase on the stability of the concentrated emulsions, with decane as the continuous medium, prepared at room temperature and heated at 60 °C for 5h, is presented in Fig. 24. The concentrated emulsion remains stable until a weight fraction of 0.2 is reached for larger values, the weight fraction which survives as concentrated emulsion decreases and becomes small for a weight fraction of 0.4. The loss of hydrophilicity caused by the increase in the amount of acrylamide accounts for the destabilization of the concentrated emulsion. 

When the monomer droplets are depleted, Interval III commences. The majority of the remaining monomer is in the latex particles with some dissolved in the aqueous phase. Particles are still able to grow, but the decreasing concentration of the monomer leads to a gradual decrease in the rate of polymerization (unless reduced diffusion of radicals because of the increasing weight fraction of polymers leads to an increase in n). Polymerization will usually continue until all the monomer has reacted. 

Figure 8.3. Profiles of the monomer conversion (X) as a function of time for the experiments with different initiator concentrations. Weight fraction of initiator (A) 4.32 x 10 , ( ) 9.62 x 1(O) 4.32 X 10 . The continuous lines represent the theoretical predictions, and the discrete points represent the experimental data taken from reference 42.

The ratio Mw/Mn (MWD) decreased with increasing PEO-MA fraction in the monomer feed and/or the number of EO units in the macromonomer. Generally, the Mw/Mn in bulk (homogeneous) systems is a function of the termination mode and the chain transfer events and varies between 1 and 2. In the present disperse systems, MWD is much broader (much above 2) as a result of further contributions, such as polymerization in the continuous phase, interface, and polymer particles. The chain transfer to PEO chains decreased the molecular weight, i,e., the Mw of copolymer decreased with increasing macromonomer concentration and PEO chain length. 

In the first method, hydrogenated styrene (H-S) monomer, dlvinyl benzene (DVB), (1 mole %) and benzoin, 0.4% by weight, were subjected to free radical polymerization via UV light exposure. The synthesis was permitted to continue until about sixty to seventy per cent (60% to 70%) conversion. At that point, the remaining styrene and DVB were removed by evaporation and replaced by an exactly equal amount of deuterated styrene (D-S) and fresh DVB and initiator. The polymerization was then permitted to continue for another several per cent. Delta fraction sizes of 5 to 20% were obtained. After the delta fraction had been synthesized in place, the remaining D-S and- DVB were again removed by evaporation, and replaced by an exactly equal amount of H-S, DVB and new Initiator. Then the reaction was permitted to continue to completion via UV exposure. 

Isotactic poly(butene-l) is produced commercially with three-component coordination-type catalysts. It is manufactured by a continuous process with simultaneous additions to the reacticMi vessel of the monomer solution, a suspension of Ti l2-Al l3, and a solution of diethyl aluminum chloride [84], The effluent containing the suspension of the product is continually removed from the reactor. Molecular weight control is achieved through regulating the reaction temperature. The effluent contains approximately 5-8% of atactic polybutene that is dissolved in the liquid carrier. The suspended isotactic fractions (92-98%) are isolated after catalyst decomposition and removal. The product has a density of 0.92 g/cnf and melts at 124—130° . 

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