Styrene-butadiene sample

Figure 6. Relaxation modulus obtained by derivating the overlapping curve of Figure 5 ( ) for the styrene-butadiene sample. Comparison with the relaxed modulus determined on a macroscopic sample (—).

FIGURE 20.14 (a) Height image of a cluster of carbon black (CB) particles. The sample was prepared by pressing the particles into a pellet, (b) Optical micrograph of a cryo-ultramicrotome cut of a mbbery composite loaded with silica, (c, d) Phase images of a nanocomposite of polyurethane (PU) loaded with silica and a mbber blend based on natural mbber (NR) and styrene-butadiene copolymer (SBR) loaded with siUca, respectively. The samples were prepared with a cryo-ultramicrotome. 

FIGURE 22.2 Flocculation behavior of the smaU-strain modulus at 160°C of uncross-linked solution-based styrene-butadiene rubber (S-SBR) composites of various molar mass with 50 phr N234, as indicated (left) and strain dependence of the annealed samples after 60 min (right). (From Kliippel, M. and Heinrich, G., Kautschuk, Gummi, Kunststoffe, 58, 217, 2005. With permission.)... 

NR, styrene-butadiene mbber (SBR), polybutadiene rubber, nitrile mbber, acrylic copolymer, ethylene-vinyl acetate (EVA) copolymer, and A-B-A type block copolymer with conjugated dienes have been used to prepare pressure-sensitive adhesives by EB radiation [116-126]. It is not necessary to heat up the sample to join the elastomeric joints. This has only been possible due to cross-linking procedure by EB irradiation [127]. Polyfunctional acrylates, tackifier resin, and other additives have also been used to improve adhesive properties. Sasaki et al. [128] have studied the EB radiation-curable pressure-sensitive adhesives from dimer acid-based polyester urethane diacrylate with various methacrylate monomers. Acrylamide has been polymerized in the intercalation space of montmorillonite using an EB. The polymerization condition has been studied using a statistical method. The product shows a good water adsorption and retention capacity [129]. 

Brandt [200] has extracted tri(nonylphenyl) phosphite (TNPP) from a styrene-butadiene polymer using iso-octane. Brown [211] has reported US extraction of acrylic acid monomer from polyacrylates. Ultrasonication was also shown to be a fast and efficient extraction method for organophosphate ester flame retardants and plasticisers [212]. Greenpeace [213] has recently reported the concentration of phthalate esters in 72 toys (mostly made in China) using shaking and sonication extraction methods. Extraction and analytical procedures were carefully quality controlled. QC procedures and acceptance criteria were based on USEPA method 606 for the analysis of phthalates in water samples [214]. Extraction efficiency was tested by spiking blank matrix and by standard addition to phthalate-containing samples. For removal of fatty acids from the surface of EVA pellets a lmin ultrasonic bath treatment in isopropanol is sufficient [215]. It has been noticed that the experimental ultrasonic extraction conditions are often ill defined and do not allow independent verification. 

Although PFE lacks a proven total concept for in-polymer analysis, as in the case of closed-vessel MAE (though limited to polyolefins), a framework for method development and optimisation is now available which is expected to be an excellent guide for a wide variety of applications, including non-polyolefinic matrices. Already, reported results refer to HDPE, LDPE, LLDPE, PP, PA6, PA6.6, PET, PBT, PMMA, PS, PVC, ABS, styrene-butadiene rubbers, while others may be added, such as the determination of oil in EPDM, the quantification of the water-insoluble fraction in nylon, as well as the determination of the isotacticity of polypropylene and of heptane insolubles. Thus PFE seems to cover a much broader polymer matrix range than MAE and appears to be quite suitable for R D samples. 

During the upcoming discussion of quantitative calibration methods, a specific example involving NIR transmission spectroscopy of 70 different styrene-butadiene copolymers [52] will be used help illustrate these methods. In this example, complete laboratory NMR analyses of all of the copolymers were available, which for each sample provided the concentrations of the four known chemical components di-butadiene, frani-butadiene, 1,2-butadiene, and styrene. The NIR spectra of these copolymer samples over the spectral range 1570-1850nm are shown in Figure 12.9. 

In the styrene-butadiene polymer example, it is not physically possible to collect spectra of the pure butadiene components (cis-, trans- and 1,2-butadiene) experimentally, because they cannot be synthesized. As a result, only the CLS method that uses estimated pure component spectra basis can be used. Using the concentrations of all four major analytes for all of the calibration samples (obtained by C NMR), it was possible to estimate the pure component spectra of the four known components (see Figure 12.11). When these estimated pure component spectra are then used to estimate the concentrations of the four constituents in the samples (Equation 12.38), it is found that the RMSEE for cA-butadiene is 1.53. 

Figure 12.26 Plot of the calibration error (RMSEE) and the validation error (RMSEP) as a function of the number of latent variables, for the case where 63 of the styrene-butadiene copolymer samples were selected for calibration, and the remaining seven samples were used for validation.

The samples we used were vulcanizates of natural rubber (NR) and styrene-butadiene copolymer rubbers (SBR), carbon-filled and unfilled. Table 1 summarizes their preparative data. Incompressibility of these vulcanizates and some other vulcanizates were checked by dipping, stretching uniaxially, and weighing a specimen in water. 

Table 11. Eight-hour time-weighted average exposure levels of butadiene in personal breathing-zone samples at a plant producing styrene-butadiene polymer in the Netherlands, 1990-97...

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The Delta Mooney (A Mooney) test is an extension of the Mooney used on empirical grounds as a general indication of processibility for non-pigmented oil extended emulsion styrene/butadiene rubber. It quantifies the changes that occur in Mooney viscosity with time, either as the difference between viscosities recorded at two specified times or as the difference between the minimum viscosity recorded immediately after the commencement of the test and the subsequent maximum viscosity. Several alternative Delta Mooney values are defined depending on the times, whether minimum/maximum viscosity difference is used and whether or not the sample has been massed on a mill. Procedures for Delta Mooney are standardised in ISO 289-341, BS 903 Part A58-142 and in ASTM D334643. 

The block copolymers were AB type styrene-butadiene block copolymers prepared by anionic polymerization. Unless specified differently in the text, a block copolymer of number average molecular weight 110,000 containing 70 wt % styrene and 30 wt % butadiene (S30B) was used. Samples of different composition used in one series of experiments had approximately the same molecular weight. 

Following the guidelines established by Schechter s work, we dispersed titanium dioxide particles in 1% solutions of carboxylated styrene-butadiene block copolymers and stirred the dispersions at elevated temperatures in a nitrogen atmosphere. Typical data are shown in Table I. The dispersions (primary dispersions) in o-dichlorobenzene were quite stable. The titanium dioxide particles were isolated from these primary dispersions by centrifugation and were washed with toluene and finally with methanol. After drying in vacuo, samples of the block copolymer-titanium dioxide composites were submitted for carbon analysis. The... 

A specific example is used to illustrate the MLR methods, as well as the other quantitative calibration methods discussed in this section. In this example, a total of 70 different styrene-butadiene copolymers were analyzed by NIR transmission spectroscopy.39 For each of these samples, four different properties of interest were measured the concentrations of czs-butadiene units, trans-butadiene units, 1,2-butadiene units, and styrene units in the polymer. The NIR spectra of these samples are overlayed in Figure 8.12. These spectra contain 141 X-variables each, which cover the wavelength range of 1570-1850 nm. 

In order to assess the optimal complexity of a model, the RMSEP statistics for a series of different models with different complexity can be compared. In the case of PLS models, it is most common to plot the RMSEP as a function of the number of latent variables in the PLS model. In the styrene—butadiene copolymer example, an external validation set of 7 samples was extracted from the data set, and the remaining 63 samples were used to build a series of PLS models for ris-butadicne with 1 to 10 latent variables. These models were then used to predict the ris-butadicne of the seven samples in the external validation set. Figure 8.19 shows both the calibration fit error (in RMSEE) and the validation prediction error (RMSEP) as a function of the number of... 

Figures 4A and 4B are the ultra-thin cross-sections of OsOi+-stained two-stage (styrene//styrene-butadiene) and (styrene-butadiene/ /styrene) latex particles at the stage ratio of 50/50 (LS-10 and LS-11), respectively. Latex samples were mixed with a polymerizable monomer mix of butyl and methyl methacrylates, cured, and microtomed for examination. Figure 4A shows particle cross-sections much smaller than the actual particle size of LS-10. It appears that since the embedding monomer solution was a solvent for polystyrene, the continuous polystyrene phase was dissolved and small S/B copolymer microdomains were left behind. This is further evidence that the second-stage S-B copolymers phase-separated as microdomains within the first-stage polystyrene phase, as shown in Figures 1A and 1A. Figure 4B shows somewhat swollen and deformed particle cross-sections, suggesting that the first-stage cross-linked S-B copolymers were a continuous phase. Indeed, the former (LS-10) behaved like a hard latex, but the latter (LS-11) behaved like a soft latex.

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