Grafting-onto

Impact polystyrene contains polybutadiene added to reduce brittleness. The polybutadiene is usually dispersed as a discrete phase in a continuous polystyrene matrix. Polystyrene can be grafted onto rubber particles, which assures good adhesion between the phases. 

Acrylonitrile has been grafted onto many polymeric systems. In particular, acrylonitrile grafting has been used to impart hydrophilic behavior to starch (143—145) and polymer fibers (146). Exceptional water absorption capabiUty results from the grafting of acrylonitrile to starch, and the use of 2-acrylamido-2-methylpropanesulfonic acid [15214-89-8] along with acrylonitrile for grafting results in copolymers that can absorb over 5000 times their weight of deionized water (147). 

Reactive Flame Retardants. Reactive flame retardants become a part of the polymer by either becoming a part of the backbone or by grafting onto the backbone. Choice of reactive flame retardant is more complex than choice of an additive type. The reactive flame retardant can exert an enormous effect on the final properties of the polymer. There are also reactive halogenated compounds used as iatermediates to other flame retardants. Tables 8 and 9 Hst the commercially avaHable reactive flame retardants and iatermediates. 

Brominated Styrene. Dibromostyrene [31780-26 ] is used commercially as a flame retardant in ABS (57). Tribromostyrene [61368-34-1] (TBS) has been proposed as a reactive flame retardant for incorporation either during polymerization or during compounding. In the latter case, the TBS could graft onto the host polymer or homopolymerize to form poly(tribromostyrene) in situ (58). 

A review covers the preparation and properties of both MABS and MBS polymers (75). Literature is available on the grafting of methacrylates onto a wide variety of other substrates (76,77). Typical examples include the grafting of methyl methacrylate onto mbbers by a variety of methods chemical (78,79), photochemical (80), radiation (80,81), and mastication (82). Methyl methacrylate has been grafted onto such substrates as cellulose (83), poly(vinyl alcohol) (84), polyester fibers (85), polyethylene (86), poly(styrene) (87), poly(vinyl chloride) (88), and other alkyl methacrylates (89). 

Problems with grafting and morphological changes in the particles are reviewed (117). Vinyl acetate has been grafted onto atactic polypropylene (118) and casein (119). 

A waterborne system for container coatings was developed based on a graft copolymerization of an advanced epoxy resin and an acryHc (52). The acryhc-vinyl monomers are grafted onto preformed epoxy resins in the presence of a free-radical initiator grafting occurs mainly at the methylene group of the aHphatic backbone on the epoxy resin. The polymeric product is a mixture of methacrylic acid—styrene copolymer, soHd epoxy resin, and graft copolymer of the unsaturated monomers onto the epoxy resin backbone. It is dispersible in water upon neutralization with an amine before cure with an amino—formaldehyde resin. 

In 1975 Wacker-Chemie introduced silicones under the name of m-polymers. These are also room temperature curing liquid polymers which give rubbery materials on cross-linking and are available both as one- and two-component systems. Their particular feature is that they contain dispersions of copolymers such as those of styrene and n-butyl acrylate in the shape of rods or rice grains in the fluid silicone polymer. A small amount of the organic copolymer is also grafted onto the silicone backbone. 

The first drugs in this class to be introduced into clinical practice are simple derivatives of 5-nitrofurfural (18). Thus, the oxime is known as nitrofuroxime (19) while the semicarbazone is called nitrofurazone (20). In order to maintain better control over the distribution and metabolism of these antibacterial agents, increasingly complex side chains and rings have been grafted onto the hydrazone. 

Grafting onto A growing polymer chain P2 attacks another polymer Pi. 

Ethylacrylate (EA) and butylacrylate (BA) was grafted onto natural rubber using BPO as the initiator [25]. KPS and AIBN were ineffective in the production of the graft and the failure to form the graft is attributed to the initiator effect. ... 

The reactivity of different monomers toward grafting onto natural rubber using different radical initiators was found to be ... 

Following the findings of Mino and Kaizerman [51] that ceric ion can form a redox system with cellulose, grafting onto various natural polymers has been carried out by the ceric ion method. In the case of cellulose, the reaction between ceric ion and cellulose occurs to produce active sites on cellulose in the following manner ... 

Polymers are classified according to their chemical structures into homopolymers, copolymers, block copolymers, and graft copolymers. In a graft copolymer, sequences of one monomer are grafted onto a backbone of the other monomer and can be represented as follows ... 

By using this technique acrylamide, acrylonitrile, and methyl acrylate were grafted onto cellulose [20]. In this case, oxidative depolymerization of cellulose also occurs and could yield short-lived intermediates [21]. They [21] reported an electron spin resonance spectroscopy study of the affects of different parameters on the rates of formation and decay of free radicals in microcrystalline cellulose and in purified fibrous cotton cellulose. From the results they obtained, they suggested that ceric ions form a chelate with the cellulose molecule, possibly, through the C2 and C3 hydroxyls of the anhy-droglucose unit. Transfer of electrons from the cellulose molecule to Ce(IV) would follow, leading to its reduction... 

Another binary mixture, namely, (acrylic acid/ acrylamide) was grafted onto carboxy methyl cellulose (CMC) [25]. 

As in the case of ceric and vanadium ions, the reaction of organic compounds with Co(III) proceeds via formation of an intermediate complex. Such a complex decomposes and produces free radicals capable of initiating vinyl polymerization. However, only a few reports on Co(IIl) ion-initiated grafting onto cellulose fibers are available [38]. 

The photo-induced process of modification of cellulose and its derivatives was reported by Geacintov and coworkers [67,68]. Thus, acrylonitrile, vinyl acetate, styrene, MMA, and the binary system of styrene and AN were grafted onto cellulose and cellulose derivatives. In... 

Photo-induced grafting onto wood cellulose with several vinyl monomers using phenyl acetophenone and benzophenone derivatives as photosensitizers has been reported [72]. A fast increase in grafting was observed for short irradiation times, whereas longer ones resulted in a decreased percent grafting. 

To sum up, the optimum conditions for methylmethacrylate grafting onto pulp by the ceric ion redox system can be summarized as follows the grafting is done at 30°C for a 1-h reaction time, using liquor ratio 40 1, acid concentration 1%, initiator concentration 0.1%, and monomer 1 mL/g pulp. 

When the AAM monomer was grafted onto polymer films, the grafted films showed much higher water absorption than the original ungrafted films. This is due to... 

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