Styrene vinyl acetate

We might be hard pressed to estimate the individual resonance stabilization energies in Eqs. (7.23) and (7.24), but the qualitative apphcation of these ideas is not difficult. Consider once again the styrene-vinyl acetate system ... 

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). 

Vinyl acetate is a colorless, flammable Hquid having an initially pleasant odor which quickly becomes sharp and irritating. Table 1 Hsts the physical properties of the monomer. Information on properties, safety, and handling of vinyl acetate has been pubUshed (5—9). The vapor pressure, heat of vaporization, vapor heat capacity, Hquid heat capacity, Hquid density, vapor viscosity, Hquid viscosity, surface tension, vapor thermal conductivity, and Hquid thermal conductivity profile over temperature ranges have also been pubHshed (10). Table 2 (11) Hsts the solubiHty information for vinyl acetate. Unlike monomers such as styrene, vinyl acetate has a significant level of solubiHty in water which contributes to unique polymerization behavior. Vinyl acetate forms azeotropic mixtures (Table 3) (12). 

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). 

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. 

Thus, a mixture of simple carbonyls Me(CO)n and halides should behave as a photoinitiator of free radical polymerization. Many such systems have been found to function in this way. Complexes formed by irradiation of Fe(CO)5 in the presence of a vinyl monomer (M) (such as MMA, styrene, vinyl acetate, propylene, and vinyl ether) have been studied by Koerner Von Grustrof and colleagues [12,13] and shown to have the chemical struc-... 

Uses. There are about forty to fifty organic peroxides commercially available in more than seventy formulations designed for specific applications which include (1) initiators for vinyl monomer polymerizations, and copolymerizations of monomers such as vinyl chloride, ethylene, styrene, vinyl acetate, acrylics, fluoroolefms and buta-dienestyrene (2) curing agents for thermoset polyesters, styrenated alkyds and oils, silicone rubbers and poly allyl diglycol carbonates ... 

Styrene Styrene Styrene Vinyl acetate Vinyl acetate Maleic anhydride Methyl acrylate... 

For the remaining three systems, styrene-vinyl acetate, vinyl acetate-vinyl chloride, and methyl acrylate-vinyl chloride, one reactivity ratio is greater than unity and the other is less than unity. They are therefore nonazeotropic. Furthermore, since both ri and 1/7 2 are either greater than or less than unity, both radicals prefer the same monomer. In other words, the same monomer—styrene, vinyl chloride, and methyl acrylate in the three systems, respectively—is more reactive than the other with respect to either radical. This preference is extreme in the styrene-vinyl acetate system where styrene is about fifty times as reactive as vinyl acetate toward the styrene radical the vinyl acetate radical prefers to add the styrene monomer by a factor of about one hundred as compared with addition of vinyl acetate. Hence polymerization of a mixture of similar amounts of styrene and vinyl acetate yields an initial product which is almost pure polystyrene. Only after most of the styrene has polymerized is a copolymer formed... 

A Japanese patent72) claims the synthesis of thermally stable copolymers by free-radical terpolymerization of dialkylstannyl dimethacrylates, glycidyl methacrylate and vinyl monomers (vinyl chloride, styrene, vinyl acetate, etc.). The products contain 0.5 to 30% tin and 0.05 to 7 % epoxide oxygen. 

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). 

Radical chain polymerizations are characterized by the presence of an autoacceleration in the polymerization rate as the reaction proceeds [North, 1974], One would normally expect a reaction rate to fall with time (i.e., the extent of conversion), since the monomer and initiator concentrations decrease with time. However, the exact opposite behavior is observed in many polymerizations—the reaction rate increases with conversion. A typical example is shown in Fig. 3-15 for the polymerization of methyl methacrylate in benzene solution [Schulz and Haborth, 1948]. The plot for the 10% methyl methacrylate solution shows the behavior that would generally be expected. The plot for neat (pure) monomer shows a dramatic autoacceleration in the polymerization rate. Such behavior is referred to as the gel effect. (The term gel as used here is different from its usage in Sec. 2-10 it does not refer to the formation of a crosslinked polymer.) The terms Trommsdorff effect and Norrish-Smith effect are also used in recognition of the early workers in the field. Similar behavior has been observed for a variety of monomers, including styrene, vinyl acetate, and methyl methacrylate [Balke and Hamielec, 1973 Cardenas and O Driscoll, 1976, 1977 Small, 1975 Turner, 1977 Yamamoto and Sugimoto, 1979]. It turns out that the gel effect is the normal ... 

A special situation arises when one of the monomer reactivity ratios is much larger than the other. For the case of r >> r2 (i.e., r S> 1 and ri propagating species preferentially add monomer M,. There is a tendency toward consecutive homopolymerization of the two monomers. Monomer Mj tends to homopolymerize until it is consumed monomer M2 will subsequently homopolymerize. An extreme example of this type of behavior is shown by the radical polymerization of styrene-vinyl acetate with monomer reactivity ratios of 55 and 0.01. (See Sec. 6-3b-l for a further discussion of this comonomer system.)... 

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

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. 

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. 

For example polymethyl acrylate was treated with phosphorus penta-chloride to form copolymers containing 26.6 and 37.8% acid chloride units these copolymers, by treatment with tert-butyl hydroperoxide, yield 4.9 to 6% perester containing polymers which were used for grafting styrene, vinyl acetate, acrylonitrile (177). 

Platinum complexes, [PtCl2 (l ,l )-XantBino ] (2) and its S,S analogue, were treated with tin(II) chloride to form the pre-catalyst for chemo-, regio-, and enantio-selective hydroformylation of styrene, vinyl acetate and allyl acetate. Although the reaction showed good chemo- and regio-selectivities, only moderate ee was obtained.103... 

Off-odor forming residual raw materials can be further subdivided into residual monomers, e.g. styrene, vinyl acetate, acrylic esters, and residual solvents e.g. ethyl acetate. The presence of such residual raw materials can be deduced from knowledge of the chemical composition of the packaging, which allows them to be specifically searched for and quantitatively analyzed. 

The same authors132) studied the copolymerization of short co-methacryloyl-PMMA macromonomers with monomers such as styrene, vinyl acetate and acrylonitrile using AIBN as the initiator. They found that the copolymers formed are free of homopolymer these graft copolymers possessing a small number of very short grafts exhibit properties similar to those of the backbone chains. 

Thus in radical polymerizations, elementary oxygen is always an inhibitor. Its inhibiting effects in the polymerizations of styrene, vinyl acetate, vinyl chloride, the acrylates and methacrylates, were described some years ago [89, 90]. 

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