Butadiene-styrene copolymers conversion

Butadiene-Styrene Copolymers from Ba-Mg-Al Catalyst Systems. Figure 13 shows the relationship between copolymer composition and extent of conversion for copolymers of butadiene and styrene (25 wt.7. styrene) prepared in cyclohexane with Ba-Mg-Al and with n-BuLi alone. Copolymerization of butadiene and styrene with barium salts and Mg alkyl-Al alkyl exhibited a larger initial incorporation of styrene than the n-BuLi catalyzed copolymerization. A major portion of styrene placements in these experimental SBR s are more random however, a certain fraction of the styrene sequences are present in small block runs. 

Figure 6. Effect of degree of conversion on the incorporation of styrene into a butadiene-styrene copolymer with no polar modifier present ( = 32°C,...

Polybutadiene.—Sensitized photo-oxidation of polybutadiene and butadiene -styrene copolymers has demonstrated the suceptibility of such polymers to attack by singlet oxygen/ " Conversely, quenchers of singlet oxygen act as stabilizers for the photo-oxidative decomposition of polymers containing unsaturation. Rabek and Lala have shown that a number of carotoneoids are effective stabilisers for polybutadiene. Nitroxides and their precursors have been shown to be effective antioxidants. Kelleher and co-workers found that in ABS copolymers deterioration occurs in the butadiene segments. They have also found that carbon black is an effective stabilizer. ... 

Butadiene copolymers are mainly prepared to yield mbbers (see Styrene-butadiene rubber). Many commercially significant latex paints are based on styrene—butadiene copolymers (see Coatings Paint). In latex paint the weight ratio S B is usually 60 40 with high conversion. Most of the block copolymers prepared by anionic catalysts, eg, butyUithium, are also elastomers. However, some of these block copolymers are thermoplastic mbbers, which behave like cross-linked mbbers at room temperature but show regular thermoplastic flow at elevated temperatures (45,46). Diblock (styrene—butadiene (SB)) and triblock (styrene—butadiene—styrene (SBS)) copolymers are commercially available. Typically, they are blended with PS to achieve a desirable property, eg, improved clarity/flexibiHty (see Polymerblends) (46). These block copolymers represent a class of new and interesting polymeric materials (47,48). Of particular interest are their morphologies (49—52), solution properties (53,54), and mechanical behavior (55,56). 

Figure 8. Copolymer composition variation with percent conversion. Conditions butadiene-styrene (75/25) in toluene at 30°C.

Second, the conversion of one of the blocks into another type of structure by a suitable quantitative chemical reaction, allows a broad diversification of the properties of the available block copolymers. The best example of such an opportunity is probably the hydrogenation of poly(butadiene-b-styrene) copolymers, which yields a product close to a low density poly(ethylene-b-styrene) when starting from an anionically prepared diblock (including a certain amount, ca. 10 %, of 1.2 units), while a high density poly(ethy1ene-b-styrene)... 

Structure and Composition of Diene Copolymers. One finds that most of the reported copolymerization studies on butadiene or isoprene involve styrene as comonomer. In part this is due to the early interest in styrene-butadiene synthetic rubbers. The free radical produced copolymers (GRS, usually about 20—25% styrene units) contain about 20% of its butadiene fraction in the 1,2 form. The ratio of 1,2 to 1,4 units is little affected by polymerization variables such as temperature, conversion and styrene content (39). Butadiene and styrene copolymers contain 50 to 60% 1,2-diene units when prepared by sodium catalysts at 50° (39). This behaviour is once more significantly different when lithium is used in place of sodium as can be seen in Table 3. 

Styrene is frequently used as part of some terpolymers with large practical utilization. One such copolymer is acrylonitrile-butadiene-styrene terpolymer (ABS). Usually it is made as poly(l-butenylene-graft-l-phenylethylene-co-cyanoethylene). This form of the copolymer can be made by grafting styrene and acrylonitrile directly on to the polybutadiene latex in a batch or continuous emulsion polymerization process. Grafting is achieved by the free-radical copolymerization of styrene and acrylonitrile monomers in the presence of polybutadiene. The degree of grafting is a function of the 1,2-vinyl content of the polybutadiene, monomer concentration, extent of conversion, temperature and mercaptan concentration (used for crosslinking). The emulsion polymerization process involves two steps production of a rubber latex and subsequent polymerization of styrene and acrylonitrile in the presence of the rubber latex to produce an ABS latex. 

Poly (butadiene- -styrene) was synthesized by grafting polystyrene onto polybuta diene. Styrene conversions up to 80% corresponding to G. E. of 50% were obtained. The graft copolymers were soluble over the styrene conversion range of 0 to 80%. Temperature, medium polarity, polybutadiene concentration and microstructure affect G. E. 

Measurements of butadiene-isoprene copolymers are summarized in a plot of swelling index us. 1,2- content (Figure 5). These data were obtained at 99.85% styrene conversion rather than 99.50% (Figures 3 and 4), and this difference must be kept in mind. Crosslinking also increases with increasing... 

A number of important commercial resins are manufactured by suspension polymerization, including poly(vinyl chloride) and copolymers, styrene resins [general purpose polystyrene, EPS, high impact polystyrene (HIPS), poly(styrene-acrylonitrile) (SAN), poly(acrylonitrile-butadiene-styrene) (ABS), styrenic ion-exchange resins], poly(methyl methacrylate) and copolymers, and poly(vinyl acetate). However, some of these polymers rather use a mass-suspension process, in which the polymerization starts as a bulk one and, at certain conversion, water and suspending agents are added to the reactor to form a suspension and continue the polymerization in this way up to high conversions. No continuous suspension polymerization process is known to be employed on a... 

Variation of Styrene Content with Extent of Conversion. Figure 8 gives the relationship between copolymer composition and the extent of conversion for copolymers of butadiene and styrene (25 wt.7. styrene) prepared in toluene, at 30°C, with n-BuLi and barium salts of t-butanol and water. For comparison purposes, the copolymer composition curve is shown for the reaction initiated using n-BuLi alone. Copolymerization using n-BuLi results in very little incorporation of styrene into the copolymer chain until about 757. conversion, after which the styrene content increases very rapidly. In contrast, copolymerization using the barium salts and n-BuLi results in an increased incorporation of styrene at the same extents of conversion. 

Schulze and Crouch [7] observed that the viscosity of the soluble fraction of copolymers from butadiene and styrene decreased sharply with the conversion after an initial increase up to the point of gelation. This decrease could not be solely attributed to a selective incorporation of higher molecular mass fractions in the gel, thus leaving fractions of low molecular mass in solution. Cragg and Manson [8] reported a similar relationship between the intrinsic viscosity and the fraction of the crosslinking DVB in the ECP with styrene. Within the concentration range up to 0.1 mass % of DVB no gel was formed. Therefore, a selective removal of species with a high molecular mass could not have taken place to explain the decrease in the intrinsic viscosity observed after its increase at lower concentrations of DVB. 

Titanocene (Cp2TiR2) /alkyllithium (LiR) Styrene, butadiene or isoprene copolymers PB in cyclohexane and toluene (5 wt.%) Catalyst (bis(cyclopentadienyl) titanium dichloride) 0.4 mmol per 100 g PB PH2 0.49 MPa T 40 °C t 2 h Conversion 97% Asahi Kasei Kogyo Kabushiki Kaisha (Osaka, Japan) 62 (1985)... 

Solomon (3, h, 5.) reported that various clays inhibited or retarded free radical reactions such as thermal and peroxide-initiated polymerization of methyl methacrylate and styrene, peroxide-initiated styrene-unsaturated polyester copolymerization, as well as sulfur vulcanization of styrene-butadiene copolymer rubber. The proposed mechanism for inhibition involved deactivation of free radicals by a one-electron transfer to octahedral aluminum sites on the clay, resulting in a conversion of the free radical, i.e. catalyst radical or chain radical, to a cation which is inactive in these radical initiated and/or propagated reactions. 

Bauer et al. describe the use of a noncontact probe coupled by fiber optics to an FT-Raman system to measure the percentage of dry extractibles and styrene monomer in a styrene/butadiene latex emulsion polymerization reaction using PLS models [201]. Elizalde et al. have examined the use of Raman spectroscopy to monitor the emulsion polymerization of n-butyl acrylate with methyl methacrylate under starved, or low monomer [202], and with high soUds-content [203] conditions. In both cases, models could be built to predict multiple properties, including solids content, residual monomer, and cumulative copolymer composition. Another study compared reaction calorimetry and Raman spectroscopy for monitoring n-butyl acrylate/methyl methacrylate and for vinyl acetate/butyl acrylate, under conditions of normal and instantaneous conversion [204], Both techniques performed well for normal conversion conditions and for overall conversion estimate, but Raman spectroscopy was better at estimating free monomer concentration and instantaneous conversion rate. However, the authors also point out that in certain situations, alternative techniques such as calorimetry can be cheaper, faster, and often easier to maintain accurate models for than Raman spectroscopy, hi a subsequent article, Elizalde et al. found that updating calibration models after... 

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