Elastomers polystyrene dispersion polymer

The solution is transformed to an oil-in-oil emulsion in which a polystyrene solution forms the disperse phase and the elastomer polyester component solution the continuous phase. The point of phase separation is observed experimentally by the onset of turbidity, due to the Tyndall effect. The conversion required for phase separation to occur depends basically on the solubility of the polystyrene chains in the elastomer solution, which in turn is governed by the elastomer concentration and compatibility of the two polymers. 

Styrene-butadiene block copolymer belongs to the A-B-A type thermoplastic elastomer. The principal structure of this type of polymer involves the thermoplastic rubber molecules terminated by the hard, glassy end blocks. The A and B copolymer block segments are incompatible and, consequently, separate spontaneously into two phases. Thus in the solid state, the styrene-butadiene (S-B-S) thermoplastic elastomer has two phases a continuous polybutadiene rubber phase and the dispersed glassy domains of polystyrene. The styrene plastic end blocks, called domains, act as cross-links locking the rubber phase in place. 

For example, a 50 50 blend of polystyrene (a hard, glassy polymer at ordinary temperature) and polybutadiene (an elastomer) will be hard if polystyrene is the continuous phase, but soft if polystyrene is the dispersed phase. In some cases, however, an immiscible polyblend may have both components dispersed as continuous phases. Evidently, a proper control of phase morphology is of utmost importance with immiscible blends. The size of the dispersed phase should be optimized considering the final performance of the blend. 

The thermally exfoliated graphite oxide can be dispersed in a wide variety of polymers, e.g., polyolefins, polyesters, nylons, polystyrenes, and polycarbonates, and also in elastomers. It is also possible to compoimd the thermally exfoliated graphite oxide into the monomeric precursors of these pol5miers and to effect the polymerization in the presence of the thermally exfoliated graphite oxide nanofiller. To formulate a conductive ink, solvents are added, such as N-methyl-2-pyrrolidone, dimethylformamide, tetrahydrofuran, and others (20). 

Polymer Polyols (BP Chemicals) are dispersions of polystyrene acrylonitrile copolymer particles of 0-5-F5/im in polyether polyols sterically stabilized with non-aqueous dispersants (NAD). Use of these with the conventional urethane polyols enables elastomers of relatively high hardness, high strength and exceptionally high elongation at break to be... 

Styrenic block copolymers and their compounds have been in widespread commercial use for many years, with many applications. With the latest technology, they have become particularly interesting as impact modifiers for plastics, both thermoplastics and thermosets. Most polymers are thermodynamically incompatible with others polymers and mixtures tend to separate into two phases, even when they are part of the same molecule, as in block copolymers. Poly(styrene-P-elastomer-P-styrene) copolymers, in which the elastomer is the main constituent, give a structure in which the polystyrene end-segments form separate spherical regions ( domains ) dispersed in a continuous phase. 

Rubber-modified polystyrenes, such as ABS polymers, are two-phase systems in which the elastomer component is dispersed through the rigid phase. These rubber-modified styrene polymers can be analyzed directly in the latex (or aqueous emulsion) phase. Although aqueous content can approach 99%, the overtone and combination bands of the OH of water fall between 900 and 1000 ... 

These are based on simple molecules such as an A-B-A block copolymer, where A is a polystyrene and B an elastomer segment [1,3,7,8]. If the elastomer is the main constituent, the polymers should have a morphology similar to that shown in Fig. 5.2. Here, the polystyrene end segments form separate spherical regions, that is, domains, dispersed in a continuous elastomer phase. Most of the polymer molecules have their polystyrene end segments in different domains. 

It was pointed out in Section 2.16.9 that anionic living polymerisation can be used to prepare ABA tri>block copolymers suitable for use as thermoplastic elastomers. In such copolymers the A blocks are normally of a homopolymer which is glassy and the B block is of a rubbery homopolymer (e.g. a polydiene such as polybutadiene or polyisoprene). The characteristic properties of these materials stems from the fact that two polymers which contain repeat units of a different chemical type tend to be incompatible on the molecular level. Thus the block copolymers phase separate into domains which are rich in one or the other type of repeat unit. In the case of the polystyrene-polydiene-polystyrene types of tri-block copolymers used for thermoplastic elastomers (with about 25% by weight polystyrene blocks), the structure is phase-separated at ambient temperature into approximately spherical polystyrene-rich domains which are dispersed in a matrix of the polydiene chains. This type of structure is shown schematically in Fig. 4.36 where it can be seen that the polystyrene blocks are anchored in the spherical domains. At ambient temperature the polystyrene is below its Tg whereas the polydiene is above its Tg. Hence the material consists of a rubbery matrix containing a rigid dispersed phase. 

This book covers both fundamental and applied research associated with polymer-based nanocomposites, and presents possible directions for further development of high performanee nanocomposites. It has two main parts. Part I has 12 chapters which are entirely dedicated to those polymer nanocomposites containing layered silicates (clay) as an additive. Many thermoplastics, thermosets, and elastomers are included, such as polyamide (Chapter 1), polypropylene (Chapter 4), polystyrene (Chapter 5), poly(butylene terephthalate) (Chapter 9), poly(ethyl acrylate) (Chapter 6), epoxy resin (Chapter 2), biodegradable polymers (Chapter 3), water soluble polymers (Chapter 8), acrylate photopolymers (Chapter 7) and rubbers (Chapter 12). In addition to synthesis and structural characterisation of polymer/clay nanocomposites, their unique physical properties like flame retardancy (Chapter 10) and gas/liquid barrier (Chapter 11) properties are also discussed. Furthermore, the crystallisation behaviour of polymer/clay nanocomposites and the significance of chemical compatibility between a polymer and clay in affecting clay dispersion are also considered. 

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