Solution polymerization, grafting

There are only a limited number of commercial apphcations of bulk or solution polymerization of chloroprene. These involve graft polymerization of adhesives and production of Hquid polymers. 

Table II. Liquids Useful in Solution Polymerization of Graft...

Fig. i. Percent grafting and molecular wt of side chains as a function of pyridine content (60% and less are solution polymerization) (700). 10. MRads at 340,000 Rads per hour at 25° C. O 0.025 mm thick film, 0.0025 mm thick film... 

RESINS (Acrylonitrile-Butadiene-Styrene). Commonly referred to as ABS resins, these materials are thermoplastic resins which are produced by grafting styrene and acrylonitrile onto a diene-rubber backbone. The usually preferred substrate is polybutadiene because of its low glass-transition temperature (approximately —80°C). Where ABS resin is prepared by suspension or mass polymerization methods, stereospedfic diene rubber made by solution polymerization is the preferred diene. Otherwise, the diene used is a high-gel or cross-linked latex made by a hot emulsion process. 

Anionic graft-polymerization of paraformaldehyde onto starch and dextrin has been effected in methyl sulfoxide solution, polymerization being initiated by the carbohydrate potassium alcoholate formed from the reaction of the carbohydrate with naphthalene potassium, a metallation procedure not previously described for carbohydrates.220... 

The grafting of TAA onto poly(MA-co-ABME) is carried out either by solution polymerization using dimethyl formamide as the solvent or by suspension polymerization (better yield) using dimethylformamide as the solvent and paraffin oil as the suspending medium... 

Summary Graft copolymers with poly(organosiloxane) backbone and thermoplastic side chains have been synthesized via the "grafting fi om" method based on azo- and triazene modified poly(organosiloxane)s. Initiation of free radical polymerization is possible from the polymeric azo and triazene initiators after thermal decomposition of the labile frmctions in solution. The graft products have been characterized by NMR, GPC, and DSC. Stable, free standing films can be cast from the graft copolymers. 

The system utilized in Figure 3.13 for HIPS can also be used to produce a solution polymerization ABS. This type of ABS is used in non-glossy applications. The glossy ABS is usually produced in an emulsion process in which emulsified polybutadiene latex is grafted and agglomerated and blended with a continuous phase of SAN. This blended material is then dried and pelletized. This process is not cost competitive with the continuous solution polymerization, but it produces a product with a superior balance of properties that commands a premium price. 

The surface of a porous substrate membrane is irradiated with y-ray, which causes generation of radicals on the membrane surface. Then, the membrane is immersed into a monomer solution. The graft polymerization of the monomers is initiated at the membrane surface. By choosing a very hydrophilic monomer, the hydrophilicity of the surface is increased considerably. 

Figure 4. Rubber particles (a) in impact polystyrene and made by mass (solution) polymerization (b) with grafted shell in ABS and made by emulsion polymerization.

Efficient toughening by the rubber modifier can be obtained, as discussed earlier, only if the RLP is capable of sufficient grafting to the epoxy matrix. Theoretically, the optimal linear rubber chain should possess two terminal reactive groups. Since this configuration could not be synthesized in dilute solution polymerization, a branched copolymer of nBA and ethylene dlacry-late (EDA), structure I, with a potentially higher functionality, was studied. Ethylene diacrylate is used primarily as a cross-... 

Considerable work has been done on the initiation of the vinyl fluoride by ionizing radiation much as y-radiation from a °Co source. A selection of references on this research includes Usmanov and other authors [4,48-62], Of these, Usmanov et al. [4] deal with the graft copolymerization of vinyl fluoride to some natural and synthetic polymers. Usmanov et al. [53] discuss the formation of branched polymers during radiation-induced polymerization. Gubareva et al. [54] deal with solution polymerizations. Nakamura et al. [58, 59, 61] deal with emulsion polymerizations of vinyl fluoride by radiation initiations. Usmanov et al. [60,61] discuss the effects of chain-transfer agents during radiation-initiated polymerization. Some copolymerization studies are described in Usmanov et al. [55]. 

Early examples of the precipitation approach include the aqueous solution polymerizations reported by Chaimberg et al. [53] for the graft polymerization of polyvinylpyrrolidone onto silica. The nonporous silica particles were modified with vinyltriethoxysilane in xylene, isolated and dispersed in an aqueous solution of vinylpyrrolidone. The reaction was performed at 70°C and initiated by hydrogen peroxide, after which precipitation on the surface occurred, leading to encapsulation. Nagai et al. [54] in 1989 reported on the aqueous polymerization of the quaternary salt of dimethylaminoethyl methacrylate with lauryl bromide, a surface-active monomer, on silica gel. Although the aim was to polymerize only on the surface, separate latex particles were also formed. 

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