Butadiene content

Finally, there are some limits regarding LPG fuels butadiene content (0.5 wt. % maximum, ISO 7941), the absence of hydrogen sulfide (ISO 8819) and copper strip corrosion (class 1, ISO 6251) which are not usually problems for the refiner. 

Nitrile Rubber. Nitrile mbbers are made by the emulsion copolymerization of acrylonitrile (9—50%) and butadiene (6) and designated NBR. The ratio of acrylonitrile (ACN) to butadiene has a direct effect on the properties on the nature of the polymers. As the ACN content increases, the oil resistance of the polymer increases (7). As the butadiene content increases, the low temperature properties of the polymer are improved (see Elastomers, SYNTHETIC-NITRILE RUBBER). 

The crude product contains appreciable amounts of C2, C3, and C fractions. The actual butadiene content lies between 82 and 88 per cent. If very pure material is desired the butadiene is converted into the tetrabromide and this is crystallized and reconverted to the hydrocarbon by means of zinc and alcohol. ... 

Although the nitrile rubbers employed normally contain about 35% acrylonitrile the inclusion of nitrile rubber with a higher butadiene content will increase the toughness at low temperatures. For example, whereas the typical blend cited above has an impact strength of only 0.9 ft Ibf in notch at 0°F, a blend of 70 parts styrene-acrylonitrile, 30 parts of nitrile rubber (35% acrylonitrile) and 10 parts nitrile rubber (26% acrylonitrile) will have an impact value of 4.5 ftlbfin notch at that temperature. ... 

The heat of fusion AHf (obtained from the area under the DSC melting curve) and percentage crystallinity calculated from AHf is found to be linearly dependent on butadiene content, and independent of the polymer architecture. This is shown in Figure 3. Also, the density of the block copolymers was found to be linearly dependent on butadiene content (see Figure 4). The linear additivity of density (specific volume) has been observed by other workers for incompatible block copolymers of styrene and butadiene indicating that very little change in density from that of pure components has occurred on forming the block copolymers.(32) While the above statement is somewhat plausible, these workers have utilized the small positive deviation from the linear additivity law to estimate the thickness of the boundary in SB block copolymers.(32)... 

Figure 3. The linear dependence of AH, on butadiene content in various block...

Figure 4. The linear dependence of density on butadiene content in various block copolymers. Density of amorphous HB (polyethylene) is estimated from the extrapolation of the density of HI through that of the random copolymer HBI-50 to axis where butadiene content is 100%.

Figure 8. Comparison of the stress-strain properties of the press-quenched films of HBIB to those from the homopolymers HB and HI. Composition of each polymer is denoted by the butadiene content next to the graph.

Figure 10A. Dependence of Young s modulus on butadiene content for various...

Figure IOC. Dependence of the ultimate stress on the butadiene content for various copolymer architectures.

The dynamic mechanical behavior indicates that the glass transition of the rubbery block is basically independent of the butadiene content. Moreover, the melting temperature of the semicrystalline HB block does not show any dependence on composition or architecture of the block copolymer. The above findings combined with the observation of the linear additivity of density and heat of fusion of the block copolymers as a function of composition support the fact that there is a good phase separation of the HI and HB amorphous phases in the solid state of these block copolymers. Future investigations will focus attention on characterizing the melt state of these systems to note if homogeneity exists above Tm. 

To illustrate the MLR method, the step-wise MLR calibration method is used to build a model for the cA-butadiene content in onr styrene-butadiene example case. In this case, four variables are specihed for selection, based on prior knowledge that there are fonr major chemical components that are varying inde-... 

Figure 12.10 The fit of the MLR model for c s-butadiene content in styrene-butadiene copolymers that uses four selected x-variables. The four variables were chosen by the stepwise method.

Table 12.5 The model fit (RMSEE) values of 4 different MLR models for predicting cis-butadiene content in styrene-butadiene copolymers by NIR spectroscopy using 1, 2, 3 and 4 x variables that were selected in a stepwise manner...

Figure 12.13 The percentage of explained variance in both the x data (solid line) and y data (dotted line), as a function of the number of latent variables in a PLS regression model for cis-butadiene content in styrene-butadiene copolymers.

If the copolymerizations in Problem 6-8 were carried out using cationic initiation, what would be expected qualitatively for the copolymer compositions List the copolymers in order of their increasing 1,3-butadiene content. Would copolymers be formed from each of the comonomer pairs Explain. What would be observed if one used anionic initiation ... 

The residual double bonds of poly(methyl acrylate) have been determined by bromination [9,27]. Bromination is accomplished through the addition of potassium bromide to potassium bromate in acidic medium [9]. Styrene-butadiene copolymers contain residual double bonds. The butadiene content of the copolymer has been determined by an iodine monochloride titration procedure [9],... 

The resultant polymer latex has a butadiene/styrene rubber content of 77.5% by weight, with an overall butadiene content of 73.6%. 

Retention of elongation reaches a maximum at 35 to 50% copolymer content. Higher butadiene content in the copolymer gives increased softness and elasticity. According to experimental data, the copolymer with 37% acrylonitrile has optimal efficiency in handling, homogeneity, and mechanical properties. This composition corresponds to a molar ratio of 1.5 mole of butadiene to 1 mole of acrylonitrile. 

Dynamic viscoelastic and stress-optical measurements are reported for blends of crosslinked random copolymers of butadiene and styrene prepared by anionic polymerization. Binary blends in which the components differ in composition by at least 20 percentage units give 2 resolvable loss maxima, indicative of a two-phase domain structure. Multiple transitions are also observed in multicomponent blends. AU blends display an elevation of the stress-optical coefficient relative to simple copolymers of equivalent over-all composition. This elevation is shown to be consistent with a multiphase structure in which the domains have different elastic moduli. The different moduli arise from increased reactivity of the peroxide crosslinking agent used toward components of higher butadiene content. 

The deleterious effect of too high carboxylation seems to be less pronounced with block copolymers of low butadiene content (see e.g., Table IV, exp. RD114). A simple explanation would be that highly carboxylated short chains can he flat on the substrate surface rather than... 

To illustrate the MLR method, the SMLR calibration method is used to build a model for the czs-butadiene content in the polymers. In this case, four variables are specified for selection, based on prior knowledge that there are four major chemical components that are varying independently in the calibration samples. The SMLR method chooses the four X-variables 1706, 1824, 1670, and 1570 nm, in that order. These four selected variables are then used to build an MLR regression model for czs-butadiene content, the fit of which is shown in Figure 8.13. Table 8.5 lists the variables that were chosen by the SMLR method,... 

Table 8.5 Results obtained from building styrene-butadiene copolymers a SMLR predictive model for the c/s-butadiene content in...

Table 8.6 Results obtained from building a PCR predictive model forthe c/ s-butadiene content in styrene-butadiene copolymers...

---