Monomer continued

Propagation. The initiator fragment reacts with a monomer M to begin the conversion to polymer the center of activity is retained in the adduct. Monomers continue to add in some way until molecules are formed with degree of polymerization n ... 

The molecular weight of the polymers is controlled by temperature (for the homopolymer), or by the addition of organic acid anhydrides and acid hahdes (37). Although most of the product is made in the first reactor, the background monomer continues to react in a second reactor which is placed in series with the first. When the reaction is complete, a hindered phenoHc or metal antioxidant is added to improve shelf life and processibiUty. The catalyst is deactivated during steam coagulation, which also removes solvent and unreacted monomer. The cmmbs of water-swoUen product are dried and pressed into bale form. This is the only form in which the mbber is commercially available. The mbber may be converted into a latex form, but this has not found commercial appHcation (38). 

Vinyl chloride monomer Continuous or in accordance with a procedure approved by the Health and Safety Executive... 

A detailed description of AA, BB, CC step-growth copolymerization with phase separation is an involved task. Generally, the system we are attempting to model is a polymerization which proceeds homogeneously until some critical point when phase separation occurs into what we will call hard and soft domains. Each chemical species present is assumed to distribute itself between the two phases at the instant of phase separation as dictated by equilibrium thermodynamics. The polymerization proceeds now in the separate domains, perhaps at differen-rates. The monomers continue to distribute themselves between the phases, according to thermodynamic dictates, insofar as the time scales of diffusion and reaction will allow. Newly-formed polymer goes to one or the other phase, also dictated by the thermodynamic preference of its built-in chain micro — architecture. 

Polymerization continues in stage II, and monomer continues to be supplied to the particles by the droplets in the aqueous phase. These droplets disappear when about 30% of the monomers has been converted to polymers. Polymerization continues in stage III after about 60% conversion, but all monomers must now be supplied to the macroradicals by a diffusion process in the micelles. 

These redistribution reactions of polymer molecules with other polymer molecules as well as with monomer, continue throughout the polymerization and should result in randomization of the polymer. Inasmuch as dimethylphenol is among the most reactive and diphenylphenol the least reactive of the phenols which have been oxidized successfully to linear high polymers, it appears likely that oxidation of any mixture of phenols will yield random copolymers. 

Monomer Continuous Pulsed Continuous Pulsed Continuous Pulsed... 

Monomer Continuous Pulsed Change Continuous Pulsed Change ... 

This problem could be solved if one could crease the luminous gas inside the tube and keep feeding the monomer continuously to compensate for the consumption of monomer due to the deposition. If the luminous gas phase could be kept at a small volume within the tube (typically 2 cm of the quartz tube), and the tube could be moved with respect to the luminous gas phase, then the inside wall of a considerably long (e.g., 16 m) plastic tube could be coated uniformly by LCVD [4]. 

If only a limited number of monomers combine by chemical reaction, then one talks of prepolymers, a preliminary stage of polymers, however, still showing reactive groups. They are partly applied in mixtures with similarly structured monomers. To simplify matters, the term monomer continues to be used in this book. 

Actin filaments are also dynamic, with actin monomers continuously being added at one end and removed at the other (treadmilling). 

Toyo Engineering Corp. (TOYO)/Mitsui Chemcials Inc. Polystyrene, high-impact (HIPS) Styrene monomer Continuous bulk polymerization process produces a wide range of HIPS with well-balanced mechanical properties and processability. Swing production feature also capable of producing GPPS 6 NA... 

The large variation in polymerization rates among the various 2-oxazoline monomers has been exploited for the preparation of quasi-diblock copolymers, namely, gradient copolymers with a narrow and steep monomer gradient, by statistical copolymerization of selected monomer combinations exhibiting large differences in reactivity. Such a one-pot quasi-diblock copolymer synthesis was first demonstrated for the statistical copolymerization of 2-phenyl-2-oxazoline and a much less reactive 2-perfluoroalkyl-2-oxazoline [174]. This living CROP (in nitromethane at 120 °C initiated by methyl p-nitrobenzenesulfonate) revealed complete consumption of the 2-phenyl-2-oxazoline after 2 min with only minor incorporation of the fluorinated monomer. Continuation of the polymerization for another 40 h led to full conversion of the fluorinated monomer. The... 

Polymerization of unsaturated organic compounds (monomers) is a special type of chain reaction. In a process of breaking of multiple bonds, new monomers continuously attach to the radical or ionic chain carriers. An example of this is the cationic polymerization of vinylchloride into polyvinylchloride (PVC) ... 

Polycondensation is a multistep reaction. As such, it first produces oligomers, i.e., molecules comprised of only a small number of monomers. Continuation of the process to produce polymers can either take the form of step-by-step addition of... 

Sequencing of two distillation columns. The demand for styrene monomer continues to increase. Other companies produce styrene by alkylating benzene with ethylene to ethylbenzene, fol-bwed by dehydrogenation to styrene. Our chemists have developed a new reaction path to styrene that involves other chemicals that appear to be available from our own supplies at a relatively low cost. These chemicals are toluene and methanol. We have been asked to prepare a preliminary design and economic evaluation for this new route to determine if it merits further consideration. If so, we will consider entering the styrene manufacturing business. 

Emulsion polymerization Emulsion polymerization starts with a dispersion of monomer micelles in a nonsolvent medium stabilized by appropriate surfactant molecules. Polymerization proceeds within each spherical micelle once a radical enters the micelle from the continuous phase, which finally results in a dispersion of latex. Dispersed phase (monomer), continuous phase (nonsolvent and initiator), surfactant < 1 pm, uniform in size... 

Gas phase reactors Gaseous monomers, continuous heterogeneous solid cat. PE, PP fluidized beds horizontal with weirs rotating paddles helically stirred tanks. 

A propagating polymeric radical with a PAVE active-radical center can have one of two possible reaction pathways. First, and most obvious, it can cross-pro-pagate to monomer, continuing the polymerization reaction, or it can undergo yS-scission, resulting in an acid fluoride-terminated polymer and a perfluoroalkyl radical capable of initiating further polymerization. Essentially this is a chain-transfer-to-monomer step, the details of which are outlined in Scheme 9.1 [6, 9]. 

Figure 3.33 lists a recipe for emulsion polymerization of polystyrene in a water dispersion of monomer droplets and soap micelles [20]. The reaction is started by light-sensitive, water-soluble initiators, such as benzoyl peroxide. If one compares the sizes of the dispersed droplets, one notices that the small soap micelles that contain also styrene in their interior are most likely to occasionally initiate a polymerization of the monomer on absorption of a free radical. Once initiated, the reaction continues until a second free radical molecule enters the micelle. Then the reaction is terminated, until a third radical starts another molecule. Monomers continuously add to the micelles, so that the polymerization continues. Keeping the free radical generation constant, a relatively narrow molar mass distribution can be obtained. 

The alkyllithium-initiated anionic copolymerization of diene and styrene monomers continues to be of interest because one can tailor-make copolymers with a wide range of compositional heterogeneity. Recently, kinetic studies have provided rate constant data to further clarify the factors responsible for the predominant incorporation of the less reactive diene monomer in styrene/diene copol3naerizations carried out in hydrocarbon media.They confirm that the magnitude of the rate constants for butadiene-styrene copolymerizations fall in the order results of several... 

The final stage, phase III, is characterized by complete disappearance of monomer droplets. If the steady state is not maintained by fresh monomer diffusion into the polymer particles, the polymerization rate declines. The unreacted monomer continues to polymerize at a declining rate. If this process is allowed to continue, onset of gelation can take place through chain transfer to pol5uner. 

Conformational studies on poly(decamethylene adipate) and poIy(tetra-methylene succinate) and the use of molecular orbital theory potential energy surfaces in determining polymer conformations for 2GT have also appeared. Crystallization, Crystallinity, and First and Second Order Transition Behaviour. The crystallization behaviour of 2GT, alone or in admixture with additives or modified by small amounts of co-monomers, continues to evoke considerable interest. Thus, X-iay fluorescence studies have been made on phenylmercurated... 

Roy et fl/.[62] carried out a copolymerization of MMA and nBA in microemulsion through semicontinuous addition of a monomer to the emulsion to obtain a 40 wt% solid content of latex of about 30 nm particle size using 4 wt% Dowfax 2A-1 as surfactant and 0.4 wt% acrylamide as cosurfactant. Xu et hollow-fiber device to feed the monomer continuously into... 

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