Styrene-vinyl acrylonitrile

Uses. The a2obisnitriles have been used for bulk, solution, emulsion, and suspension polymeri2ation of all of the common vinyl monomers, including ethylene, styrene vinyl chloride, vinyl acetate, acrylonitrile, and methyl methacrylate. The polymeri2ations of unsaturated polyesters and copolymeri2ations of vinyl compounds also have been initiated by these compounds. 

Physical Stabilization Process. Cellulai polystyrene [9003-53-6] the outstanding example poly(vinyl chloride) [9002-86-2] copolymers of styrene and acrylonitrile (SAN copolymers [9003-54-7]) and polyethylene [9002-88-4] can be manufactured by this process. 

In these equations I is the initiator and I- is the radical intermediate, M is a vinyl monomer, I—M- is an initial monomer radical, I—M M- is a propagating polymer radical, and and are polymer end groups that result from termination by disproportionation. Common vinyl monomers that can be homo-or copolymeri2ed by radical initiation include ethylene, butadiene, styrene, vinyl chloride, vinyl acetate, acrylic and methacrylic acid esters, acrylonitrile, A/-vinylirnida2ole, A/-vinyl-2-pyrrohdinone, and others (2). 

Many synthetic latices exist (7,8) (see Elastomers, synthetic). They contain butadiene and styrene copolymers (elastomeric), styrene—butadiene copolymers (resinous), butadiene and acrylonitrile copolymers, butadiene with styrene and acrylonitrile, chloroprene copolymers, methacrylate and acrylate ester copolymers, vinyl acetate copolymers, vinyl and vinyUdene chloride copolymers, ethylene copolymers, fluorinated copolymers, acrylamide copolymers, styrene—acrolein copolymers, and pyrrole and pyrrole copolymers. Many of these latices also have carboxylated versions. 

An a priori method for choosing a surfactant was attempted by several researchers (50) using the hydroph i1 e—1 ip oph i1 e balance or HLB system (51). In the HLB system a surfactant soluble in oil has a value of 1 and a surfactant soluble in water has a value of 20. Optimum HLB values have been reported for latices made from styrene, vinyl acetate, methyl methacrylate, ethyl acrylate, acrylonitrile, and their copolymers and range from 11 to 18. The HLB system has been criticized as being imprecise (52). 

The principal use of the peroxodisulfate salts is as initiators (qv) for olefin polymerisation in aqueous systems, particularly for the manufacture of polyacrylonitrile and its copolymers (see Acrylonitrile polymers). These salts are used in the emulsion polymerisation of vinyl chloride, styrene—butadiene, vinyl acetate, neoprene, and acryhc esters (see Acrylic ester polymers Styrene Vinyl polymers). 

Tetrachloroethylene reacts with formaldehyde and concentrated sulfuric acid at 80°C to form 2,2-dichloropropanoic acid [75-99-0] (8). Copolymers with styrene, vinyl acetate, methyl acrylate, and acrylonitrile are formed in the presence of dibenzoyl peroxide (9,10). 

Modifications of epichlorohydrin elastomers by radical-induced graft polymeri2ation have been reported. Incorporated monomers include styrene and acrylonitrile, styrene, maleic anhydride, vinyl acetate, methyl methacrylate, and vinyHdene chloride (81), acryHc acid (82), and vinyl chloride (81,83,84). When the vinyl chloride-modified epichlorohydrin polymers were used as additives to PVC, impact strength was improved (83,84). 

Free radical polymerization is a key method used by the polymer industry to produce a wide range of polymers [37]. It is used for the addition polymerization of vinyl monomers including styrene, vinyl acetate, tetrafluoroethylene, methacrylates, acrylates, (meth)acrylonitrile, (meth)acrylamides, etc. in bulk, solution, and aqueous processes. The chemistry is easy to exploit and is tolerant to many functional groups and impurities. 

Radical copolymerization is used in the manufacturing of random copolymers of acrylamide with vinyl monomers. Anionic copolymers are obtained by copolymerization of acrylamide with acrylic, methacrylic, maleic, fu-maric, styrenesulfonic, 2-acrylamide-2-methylpro-panesulfonic acids and its salts, etc., as well as by hydrolysis and sulfomethylation of polyacrylamide Cationic copolymers are obtained by copolymerization of acrylamide with jV-dialkylaminoalkyl acrylates and methacrylates, l,2-dimethyl-5-vinylpyridinum sulfate, etc. or by postreactions of polyacrylamide (the Mannich reaction and Hofmann degradation). Nonionic copolymers are obtained by copolymerization of acrylamide with acrylates, methacrylates, styrene derivatives, acrylonitrile, etc. Copolymerization methods are the same as the polymerization of acrylamide. 

This photoinitiating system is also used for the polymerization of other vinyl monomers such as styrene (St), acrylonitrile (AN), and vinylacetate (VA). The efficiency of photoinitiation by this system follows the order ... 

Several radical copolymerizations of vinyl 2-furoate with well-known monomers (50 50) were also studied. Complete inhibition was obtained with vinyl acetate, very strong retardation with styrene, vinyl chloride and acrylonitrile methyl methacrylate homopolymerized without appreciable decrease in rate. It is evident that the degree of retardation that vinyl 2-furoate imposes upon the other monomer depends on the stability of the latter s free radical. With styrene and vinyl chloride the small amounts of fairly low molecular-weight products contained units from vinyl 2-furoate which had entered the chain both through the vinyl bond and through the ring (infrared band at 1640 cm-1). 

The isoprene units in the copolymer impart the ability to crosslink the product. Polystyrene is far too rigid to be used as an elastomer but styrene copolymers with 1,3-butadiene (SBR rubber) are quite flexible and rubbery. Polyethylene is a crystalline plastic while ethylene-propylene copolymers and terpolymers of ethylene, propylene and diene (e.g., dicyclopentadiene, hexa-1,4-diene, 2-ethylidenenorborn-5-ene) are elastomers (EPR and EPDM rubbers). Nitrile or NBR rubber is a copolymer of acrylonitrile and 1,3-butadiene. Vinylidene fluoride-chlorotrifluoroethylene and olefin-acrylic ester copolymers and 1,3-butadiene-styrene-vinyl pyridine terpolymer are examples of specialty elastomers. 

Radiation Induced Reactions. Graft polymers have been prepared from poly(vinyl alcohol) by the irradiation of the polymer-monomer system and some other methods. The grafted side chains reported include acrylamide, acrylic acid, acrylonitrile, ethyl acrylate, ethylene, ethyl methacrylate, methyl methacrylate, styrene, vinyl acetate, vinyl chloride, vinyl pyridine and vinyl pyrrolidone (13). Poly(vinyl alcohols) with grafted methyl methacrylate and sometimes methyl acrylate have been studied as membranes for hemodialysis (14). Graft polymers consisting of 50% poly(vinyl alcohol), 25% poly(vinyl acetate) and 25% grafted ethylene oxide units can be used to prepare capsule cases for drugs which do not require any additional plasticizers (15). 

A similar method can be used for the addition of carbon tetrachloride to nonpolymerizable olefins (e.g., 1-octene, 2-octene, 1-butene, 2-butene) pure adducts are obtained in yields of over 90% if the components are allowed to react at 100° for 6 hours. Adducts of carbon tetrachloride with vinylic monomers (styrene, butadiene, acrylonitrile, methyl acrylate, etc.) can be prepared in good yields by substituting cupric chloride dihydrate in acetonitrile for ferric chloride hexahydrate and benzoin. 

The interest in alpha olefins as a group lies in the reactivity of the double bond, just like styrene, vinyl chloride, ethylene, propylene, or acrylonitrile. But individually, the alpha olefins of varying chain length have quite different physical characteristics and therefore different applications. For example, the C4 alpha olefin is a gas at room temperature, while the through Ci8 s are liquids and the 020" are waxy solids. 

Uses Copolymerized with methyl acrylate, methyl methacrylate, vinyl acetate, vinyl chloride, or 1,1-dichloroethylene to produce acrylic and modacrylic fibers and high-strength fibers ABS (acrylonitrile-butadiene-styrene) and acrylonitrile-styrene copolymers nitrile rubber cyano-ethylation of cotton synthetic soil block (acrylonitrile polymerized in wood pulp) manufacture of adhesives organic synthesis grain fumigant pesticide monomer for a semi-conductive polymer that can be used similar to inorganic oxide catalysts in dehydrogenation of tert-butyl alcohol to isobutylene and water pharmaceuticals antioxidants dyes and surfactants. 

Emulsion polymerization was first employed during World War II for producing synthetic rubbers from 1,3-butadiene and styrene. This was the start of the synthetic rubber industry in the United States. It was a dramatic development because the Japanese naval forces threatened access to the southeast Asian natural-rubber (NR) sources, which were necessary for the war effort. Synthetic mbber has advanced significantly from the first days of balloon tires, which had a useful life of 5000 mi to present-day tires, which are good for 40,000 mi or more. Emulsion polymerization is presently the predominant process for the commercial polymerizations of vinyl acetate, chloroprene, various acrylate copolymerizations, and copolymerizations of butadiene with styrene and acrylonitrile. It is also used for methacrylates, vinyl chloride, acrylamide, and some fluorinated ethylenes. 

Butadiene Styrene Vinyl Acetate Vinyl Methyl Methyl Chloride Methacrylate Acrylate Acrylonitrile ... 

The rates of radical-monomer reactions are also dependent on considerations of steric hindrance. This is easily observed by considering the reactivities of di, tri-, and tetrasubstituted ethylenes in copolymerization. Table 6-5 shows the kn values for the reactions of various chloroethylenes with vinyl acetate, styrene, and acrylonitrile radicals. The effect of a second substituent on monomer reactivity is approximately additive when both substituents are in the 1- or a-position. However, a second substituent when in the 2- or (3-position of the monomer results in a decrease in reactivity due to steric hindrance between it and the radical to which it is adding. Thus 2-10-fold increases and 2-20-fold decreases in the reactivities of vinylidene chloride and 1,2-dichloroethylene, respectively, are observed compared to vinyl chloride. 

COPOLYMERIZATION WITH PARTICIPATION OF MULTIMONOMERS Synthesis of various multimonomers and their copolymerization with styrene, acrylonitrile or acrylic acid was described in a set of papers. Most of the early work on the copolymerization of multimonomers with vinyl monomers employed p-cresyl formaldehyde resins, esterified by methacryloyl chloride or acryloyl chloride, as one of the comonomers, and a simple vinyl monomer such as styrene or acrylonitrile as the other monomer. 

The chain transfer reaction played an important role, particularly because of abstraction of the active hydrogen at a-carbon from the allyl group. Moreover, unreacted double bonds were present in the copolymer obtained. The influence of chain transfer reaction could be diminished by applying multimonomers which do not contain allyl groups. This was shown in the example of copolymerization of multimethacrylate prepared by esterification of poly(2-hydroxyethyl methacrylate) with methacryloyl chloride. Copolymerization of the multimethacrylate with vinyl monomers such as styrene or acrylonitrile can be represented by the reaction ... 

The copolymerization of multimonomers with vinyl monomers such as acrylic acid, styrene, or acrylonitrile results in semi-ladder copolymers soluble in many common sol-vents. Such products consist of ladder-type blocks created from multimonomer molecules and blocks of repeated units formed from vinyl monomer, both connected with branching points and fastened together by fragments of the molecule with ladder structure. Semi-ladder copolymer (multimethacrylate-acrylic acid, partially crosslinked) has the following structure ... 

Fig. 8. Polymerization of vinyl monomers by vibromilling polyamide. Effect of monomer concentration on yielding 1) styrene 2) acrylonitrile (13)...

Acrylonitrile Allyl acrylate Allyl methacrylate n-Butyl acrylate n-Butyl methacrylate Isobutyl methacrylate Divinyl benzene 2-Choroethyl methacrylate Ethyl acrylate /i-Ethoxyethyl methacrylate 2-Ethylhexyl methacrylate Ethyl methacrylate Methyl methacrylate Methylisopropenylketone Methyl vinyl ketone N-Vinyl pyrrolidone Styrene Vinylpyridine Acrylonitrile Allyl acrylate Allyl methacrylate... 

For most of these esters, the free radical polymerization procedures are very similar to each other. With minor modifications, the considerations and preparations given here may be applied to many of the other common vinyl monomers such as styrene, vinyl acetate, vinylidene chloride, acrylonitrile, and acrylamide. 

Grafted Polymers. Due to the special chain structure ABS terpoly-mers have been widely modified by grafting vinyl monomers onto the main chain. We emphasize that the method how ABS itself is obtained is addressed sometimes as grafting styrene and acrylonitrile onto a butadiene rubber. Here we focus on grafting reactions on the ABS itself. Some examples of ABS grafted polymers are shown in Table 8.7. The pending acid functionalities may be allowed to react with amines and other compounds (45). 

Internal plasticizing demands a chemical relationship between the components which constitute the product. Therefore, good effects can be expected from copolymers of styrene and isobutylene, ethylene, or diolefins like butadiene or isoprene. Internal plasticizing of PVC can be effected by copolymerizing vinyl chloride with acrylates of higher alcohols or maleates and fumarates. The important ABS products are internal copolymers of butadiene, styrene, and acrylonitrile. The hardness of the unipolymers of styrene and acrylonitrile can be modified by butadiene which, as a unipolymer, gives soft, rubberlike products. As the copolymerization parameters of most monomers are known, it is relatively easy to choose the most suitable partner for the copolymerization. When the product of the r—values is l, there is an ideal copolymerization, because the relative reactivity of both monomers toward the radicals is the same. Styrene/butadiene, styrene/vinyl thiophene, and... 

Armstrong et al. have extensively studied the effect of this radiation on grafting butadiene, styrene, vinyl chloride, vinyl esters, acrylic, and methacrylic esters, acrylonitrile and other less common monomers on Nylon 66 fibers. They observed the influence of oxygen, water, methanol, acetic acid, dose of irradiation as well as temperature (160-163). 

Guzman (53) investigated the ceric ion initiated grafting of acrylonitrile, acrylamide, methyl methacrylate, styrene, vinyl acetate, methacrylate, acrylic anhydride, and isoprene to cellulose. Intense grafting was obtained with acrylonitrile, acrylamide, methacrylate and acrylic anhydride. 

Beginning in the late forties, copolymers were fractionated by adsorption chromatography poly (butadiene-co-styrene)32 34), poly(butadiene-co-acrylonitrile)32), polystyrene- -vinyl acetate)35), poly(styrene-h-ethylene oxide)36) and poly(styrene-co-acrylonitrile) 37). HPLC adsorption chromatography was first applied to copolymer analysis by Teramachi et al. in 1979 38>. 

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