Styrene monomer polymer

Betancourt-Galindo R, Saldivar R, Rodriguez-Femandez OS, et al. (2004) Preparation and characterization of magnetic latexes using styrene monomer. Polym Bull 51 395 02... 

Chloromethylated polystyrene - - Styrene monomer Polymer characterisation, monomer yield decreased with increasing chlorine content of polymer [49]... 

Acrylics. Acetone is converted via the intermediate acetone cyanohydrin to the monomer methyl methacrylate (MMA) [80-62-6]. The MMA is polymerized to poly(methyl methacrylate) (PMMA) to make the familiar clear acryUc sheet. PMMA is also used in mol ding and extmsion powders. Hydrolysis of acetone cyanohydrin gives methacrylic acid (MAA), a monomer which goes direcdy into acryUc latexes, carboxylated styrene—butadiene polymers, or ethylene—MAA ionomers. As part of the methacrylic stmcture, acetone is found in the following major end use products acryUc sheet mol ding resins, impact modifiers and processing aids, acryUc film, ABS and polyester resin modifiers, surface coatings, acryUc lacquers, emulsion polymers, petroleum chemicals, and various copolymers (see METHACRYLIC ACID AND DERIVATIVES METHACRYLIC POLYMERS). 

The reaction rate of fumarate polyester polymers with styrene is 20 times that of similar maleate polymers. Commercial phthaHc and isophthaHc resins usually have fumarate levels in excess of 95% and demonstrate full hardness and property development when catalyzed and cured. The addition polymerization reaction between the fumarate polyester polymer and styrene monomer is initiated by free-radical catalysts, commercially usually benzoyl peroxide (BPO) and methyl ethyl ketone peroxide (MEKP), which can be dissociated by heat or redox metal activators into peroxy and hydroperoxy free radicals. 

The free styrene monomer is restrained within the gel and further reaction with fumarate groups is determined by the spacial arrangement the styrene polymerizes in homopolymer blocks as it intercepts fumarate reaction sites. As individual micelles expand and deplete available fumarate sites in the short polymer chains, the remaining styrene forms homopolymer blocks that terminate at the boundaries between overlapping micelles (Fig. 4). 

In these mbber-modified polystyrene polymers, the mbbers should have low T, large particle sizes (0.5—5 J.m), graftable and cross-linkable sites, and should be compatible with styrene monomer (93). Polybutadiene, with a T of —SS C, meets all of these requirements and is used most frequently. These mbber-modified systems exhibit excellent low temperature impact strength, a required attribute for use in refrigerators. 

Today the common practice is first to dissolve the rubber in the styrene monomer and then to polymerise the styrene in the usual way. By this process the resultant blend will contain not only rubber and polystyrene but also a graft polymer where short styrene side chains have been attached to the rubber molecules. This gives a marked improvement in the impact strengths that can be obtained. 

Occupational and environmental exposure to chemicals can take place both indoors and outdoors. Occupational exposure is caused by the chemicals that are used and produced indoors in industrial plants, whereas nonoccupa-tional (and occupational nonindustrial) indoor exposure is mainly caused by products. Toluene in printing plants and styrene in the reinforced plastic industry are typical examples of the two types of industrial occupational exposures. Products containing styrene polymers may release the styrene monomer into indoor air in the nonindustrial environment for a long time. Formaldehyde is another typical indoor pollutant. The source of formaldehyde is the resins used in the production process. During accidents, occupational and environmental exposures may occur simultaneously. Years ago, dioxin was formed as a byproduct of production of phenoxy acid herbicides. An explosion in a factory in... 

Styrene-based polymer supports are produced by o/w suspension polymerization of styrene and divinylbenzene. Suspension polymerization is usually carried out by using a monomer-soluble initiator such as benzoperoxide (BPO) or 2,2-azo-bis-isobutylnitrile (AIBN) at a temperature of 55-85°C (19). A relatively high initiator concentration of 1-5% (w/w) based on the monomer is used. The time required for complete monomer conversion must be determined by preliminary experiments and is usually between 5 and 20 h, depending on the initiator concentration, the temperature, and the exact composition of the monomer mixture (11-18). 

Steric factors appear to be dominant in determining AHv and ASP. The resonance energy lost in converting monomer to polymer is of secondary importance for most common monomers. It is thought to account for A//, for VAc and VC being lower than for acrylic and styrenic monomers. 

Low Conversion Reactors. The major problem in temperature control in low conversion reactors is the orders cf magnitude increase in viscosity as the conversion increases. Fig.8 shows the viscosity of a polystyrene solution as the function of percent PS. The data are for polystyrene with a Staudinger molecular weight of 60,000 at 100 C and 150 C in a cumene solution, a satisfactory analog for styrene monomer solutions. As the polymer concentration increases from 0 to 60%, viscosity increases from about 1 cp to 10 cp. 

Reaction Mechanism. The reaction mechanism of the anionic-solution polymerization of styrene monomer using n-butyllithium initiator has been the subject of considerable experimental and theoretical investigation (1-8). The polymerization process occurs as the alkyllithium attacks monomeric styrene to initiate active species, which, in turn, grow by a stepwise propagation reaction. This polymerization reaction is characterized by the production of straight chain active polymer molecules ("living" polymer) without termination, branching, or transfer reactions. 

The thermally-initiated styrene system is considerably simpler than most industrial applications. Though these experiments provided useful guidelines, it was difficult to develop broadly applicable design criteria without carefully evaluating a broad range of monomer, polymer and initiator systems. Hence we extended our kinetic model to some other monomer systems such as styrene and methyl methacrylate using common initiators such as benzoyl peroxide (BPO) and... 

Certain commercially important crosslinking reactions are carried out with unsaturated polymers. For example, as will be described later in this chapter, polyesters can be made using bifunctional acids which contain a double bond. The resulting polymers have such double bonds at regular intervals along the backbone. These sites of unsaturation are then crosslinked by reaction with styrene monomer in a free-radical chain (addition) process to give a material consisting of polymer backbones and poly(styrene) copolymer crosslinks. 

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