SBS triblock copolymer

A new process to develop interface vulcanization is grafting of selective accelerators onto a polymer chain, which in the subsequent process of vulcanization acts as an effective cure accelerator for the second polymer component in the blend. Beniska et al. [6] prepared SERFS blends where the polystyrene phase was grafted with the accelerator for curing SBR. Improved hardness, tensile strength, and abrasion resistance were obtained. Blends containing modified polystyrene and rw-1,4-polybutadiene showed similar characteristics as SBS triblock copolymers. 

FIGURE 5.7 Phase separation in styrene-butadiene-styrene (SBS) triblock copolymer. The isolated spherical styrene domains form the hard phase, which act both as intermolecular tie points and filler. The continuous butadiene imparts the elastomeric characteristics to this polymer. MW = molecular weight. (From Grady, B.P. and Cooper, S.L., Science and Technology of Rubber, Mark, J.E., Erman, B., and Eirich, F.R. (eds.). Academic Press, San Diego, CA, 1994. With permission.)... 

The above equations gave reasonably reliable M value of SBS. Another approach to modeling the elastic behavior of SBS triblock copolymer has been developed [202]. The first one, the simple model, is obtained by a modification of classical rubber elasticity theory to account for the filler effect of the domain. The major objection was the simple application of mbber elasticity theory to block copolymers without considering the effect of the domain on the distribution function of the mbber matrix chain. In the derivation of classical equation of rabber elasticity, it is assumed that the chain has Gaussian distribution function. The use of this distribution function considers that aU spaces are accessible to a given chain. However, that is not the case of TPEs because the domain also takes up space in block copolymers. 

Synthesis of vinyl block copolymers is accomplished by living polymerisation, mostly by anionic polymerisation. Several strategies can be used, illustrated here by the example of the Styrene-Butadiene-Styrene (or SBS) triblock copolymer. 

The data in Table III illustrate that the addition of polypropylene showed an improvement in physical properties similar to the commercially available SBS triblock copolymer. This TPE, shown in Table III, shows outstanding physical properties. This unique block copolymer can only be made using the anionic polymerization technique. 

A Study of the Flow Properties of a Styrene-Methylmethacrylate Diblock Copolymer and SBS Triblock Copolymers... 

Sample Materials. A styrene-butadiene-styrene (SBS) triblock copolymer from Phillips Petroleum named Solprene 414C was studied in the investigation. 

SBS-Triblock Copolymers (40% Styrene). The following values were used in calculation of Tcr for Solprene 414C ... 

ABA triblock copolymers cannot be produced by monofiinctional initiation when the A anion is not sufficiently basic to initiate polymerization of B monomers. In such cases the bifunctional initiators like alkali metal complexes of polycyclic aromatic compounds (e.g., naphthalene and biphenyl) can be used to produce ABA triblock copolymers. In these cases polymerization would be started with monomer B to produce a polymeric dianion which would initiate polymerization of the A monomer that is added later. The process is illustrated below for the commercially important styrene-butadiene-styrene (SBS) triblock copolymer ... 

SBS Triblock Copolymer used was Kraton D1101 (Styrene/Butadiene Ratio 30/70). 

It has been found in the study of PVME and SBS triblock copolymer that solubility of PVME in PS block copolymer domains is larger than in PS homopolymer. This may indicate that the mixing enthalpy has an effect on the blend miscibility [Xie et al., 1993]. The behavior has been attributed to the effect of PB segments in SBS. The phase equilibria and miscibility in polymer blends containing random or block copolymer was reviewed [Roe and Rigby, 1987]. More recent data are presented in Chapter 4 Interphase and Compatibilization by Addition of a Compatibilizer in this Handbook. 

The outstanding behavior of these rubbers arises from the natural tendency of two polymer species to separate. However, this separation is restrained in these polymers since the blocks are covalently linked to each other. In a typical commercial SBS triblock copolymer with about 30% styrene content, the styrene blocks congregate into rigid, glassy domains which act effectively to link the butadiene segments into a network (Figure 4.7) analogous to that of cross-linked rubber. 

The appropriate amount of dicumyl peroxide was added and the second step of "dynamic covulcanization" took place. In this way vulcanizates with rheological properties, similar to those of SBS triblock copolymers, were obtained (Fig. 1). Unfortunately, their mechanical... 

It was found that mixtures of modified polystyrene with elastomers, e.g. cis-1,4-polybutadiene, behave like the SBS triblock copolymers. The changes of the shear modulus as a function of temperature are similar in both cases mentioned above but quite different from the ordinary mixture of polystyrene and polybutadiene (Fig. 9). 

Other experiments. In the same semi-batch equipment one experiment was performed using methanol to precipitate the PPE instead of CO2. In another experiment a Styrene-Butadiene-Styrene (SBS) triblock copolymer was precipitated from cyclohexane by adding CO2 as an anti-solvent. This synthetic rubber contains blocks with a glass transition temperature of 100°C (polystyrene) and blocks with a glass transition temperature of approximately -100°C (polybutadiene). 

Schematic figures of the shape memory mechanism of the styrene-butadiene-styrene (SBS) triblock copolymer/poly(e-caprolactone) (PCL) blend in (a)-(d). (Adapted from Zhang, H., Wang, H., Zhong, W, and Du, Q. 2009. A novel type of shape memory polymer blend and the shape memory mechanism. Polymer 50 1596-1601. Copyright Elsevier Ltd. Reproduced with permission.)...

FIGURE 7 Illustration of phase separation in SBS triblock copolymers normally used as a thermoplastic elastomer. The isolated spherical styrene domains form the hard phase, which acts as both intermolecular tie points and filler. The continuous butadiene imparts the elastomeric characteristics to this polymer. 

Kim, G. Libera, M. Microstructural development in solvent-cast polystyrene-polybutadiene-polystyrene (SBS) triblock copolymer thin films. Macromolecules 1998,31, 2569-2577. Bates, F.S. Polymer-polymer phase behaviour. Science 1991, 251, 898-905. 

An oil-soluble initiator and stabiliser were dissolved in styrene monomer, and an SBS triblock copolymer then added to the styrene solution. The resulting solution was added to an aqueous solution of sodium lauryl sulphate surfactant to form a crude emulsion which was then... 

FIG. 1, Schematic diagrams of SBS triblock copolymer morphologies, for spherical or cylindrical domains (top two) and lamellar structures (bottom). The interphase is labeled S + B. 

Three SBS triblock copolymers with different compositions and block lengths (Table 1) were obtained from Shell Development Co, they are designated here as 0.48 PS, 0.29 PS, and 0,27 PS to reflect their polystyrene (PS) content. It should be noted that two of these have comparable PS... 

In block copolymers with lamellar morphology, mechanical properties and deformation structures vary with the orientation of the lamellae with respect to the direction of applied load. When the material is loaded in a perpendicular direction to the lamellar orientation, lamellae are folded in a fish-bone-like arrangement (57). Such a lamellar folding in a solution cast film of an SBS triblock copolymer is shown in Figure 20 (58). 

Microphase-separated block copolymer films have been investigated by numerous authors (257,258). van den Berg and co-workers reported on the film structures of poly(styrene-6Zoc butadiene-6Zoc -styrene) (SBS) triblock copolymers of PB and PS (259). In particular, the effect of film thickness on the observed morphology was unraveled for this system. 

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