Styrene-Isoprene Kraton

Styrenic SBS/SIS (styrene-isoprene-styrene block copolymers) CariflexTR, Kraton... 

Kraton 1107 brand elastomer was from Shell Chemical Co., and it is synthesized by coupling the isoprenyl anion ends of a styrene/isoprene (SI) block copolymer to give styrene/isoprene/styrene (SI IS). Proton NMR analysis indicated 84% (wt.) isoprene and 16% (wt.) styrene. 

It is important to appreciate that polymer produced by an anionic chain-growth mechanism can have drastically different properties from one made by a normal free radical reaction. Block copolymers can be synthesized in which each block has different properties. We mentioned in Chapter 4 that Michael Szwdrc of Syracuse University developed this chemistry in the 1950s. Since that time, block copolymers produced by anionic polymerization have been commercialized, such as styrene-isoprene-styrene and styrene-butadiene-styrene triblock copolymers (e.g., Kraton from Shell Chemical Company). They find use as thermoplastic elastomers (TPE), polymers that act as elastomers at normal temperatures but which can be molded like thermoplastics when heated. We will discuss TPEs further in Chapter 7. 

General Description Kraton Polymers are a range of unhydrogenated styrenic block copolymers, compounds with an unsaturated rubber midblock (styrene-butadiene-styrene [SBS] and styrene-isoprene-styrene [SIS])J ° ]... 

Krameria argentea extract Krameria extract Krameria triandra extract. See Rhatany extract Kraton D 1101] Kraton D 1102. See Styrene/butadiene/styrene block copolymer Kraton D 1107] Kraton D 1107P] Kraton D 1111] Kraton D 1112P. See Styrene/isoprene/styrene block copolymer Kraton D 1116. See Styrene/butadiene polymer... 

Kraton D1117P. See Styrene/isoprene/styrene block copolymer Kraton D 1118X. See Styrene/butadiene/styrene block copolymer Kraton D 1119P. See Styrene/isoprene/styrene... 

Kraton D 1125P. See Styrene/isoprene/styrene block copolymer... 

The most extensively studied block copolymers prepared by anionic polymerization are the styrene-butadiene or styrene-isoprene rubbers. Shell Chemical Company s Kraton thermoplastic elastomers are ABA block copolymers of this type. Their elastomeric properties are excellent, yet they differ from other rubbers in that vulcanization is not required. These elastomers consist of a rubbery polybutadiene matrix with the styrene segments serving as anchors in thermoplastic microdomains. 

Thermoplastic rubber is a relatively new class of polymer. It has the solubility and thermoplasticity of polystyrene, while at ambient temperatures it has the toughness and resilience of vulcanized natural rubber or polybutadiene. These rubbers are actually block copolymers. The simplest form consists of a rubbery mid-block with two plastic end blocks (A-B-A), as shown in Figure 5.7. Examples of commercial products are Kraton and Solprene . These materials are often compounded with plasticizers to decrease hardness and modulus, eliminate drawing, enhance pressure-sensitive tack, improve low-temperature flexibility, reduce melt and solution viscosity, decrease cohesive strength or increase plasticity if desired, and substantially lower material costs. Low levels of thermoplastic rubbers are sometimes added to other rubber adhesives. These materials are used as components in the following applications PSAs, hot-melt adhesives, heat-activated-assembly adhesives, contact adhesives, reactive contact adhesives, building construction adhesives, sealants, and binders. Two common varieties of thermoplastic rubber adhesives are styrene-butadiene-styrene (S-B-S) and styrene-isoprene-styrene (S-I-S). ... 

Styrene block copolymers are the most widely used TPEs. Styrenic TPEs are usually styrene butadiene styrene (SBS), styrene ethylene butadiene styrene (SEES), and styrene isoprene styrene (SIS). Styrenic TPEs usually have about 30 0 percent bound styrene. Principal styrenic TPE markets are molded shoe soles and other footwear, extruded film/sheet and wire/cable covering, and pressure-sensitive and hot-melt adhesives. They are also popular as grips for bike handles, kitchen utensils, clear medical products, and personal care products. Styrenic block copolymer thermoplastic elastomers are produced by Shell Chemical (Kraton), Firestone Synthetic Rubber and Latex, Division of Bridgestone/Firestone (Stereon), Dexco Polymers (Vector), EniChem Elastomers (Europrene), and other companies. 

Well-known materials are the Kraton polymer range, originally developed by Shell, and are produced in several types. The D series has an unsaturated rubber midblock - styrene/butadiene/styrene (SBS), and styrene/isoprene/styrene (SIS) - and the G series has a saturated midblock - styrene ethylene/butylene styrene (SEES) and styrene ethylene/propylene (SEP). The G series has increased resistance to oxidation and weathering, higher service temperature and better processing stability. 

Figure 4.11 Variations of the average relaxation time associated with the copolymer exchange in solutions of poly(styrene)-poly(hydrogenated isoprene) (Kraton G-1701) in dioxane/heptane mixtures. Left effect of temperature at heptane volume fraction 100% (o) and 95% (A). Right effect of the heptane volume fraction at 298 K. Reproduced from Reference 81 with permission of Elsevier.

Shell Chemical/Kraton Corp. also produces styrene isoprene tri-block copolymers as well as styrene-hydrogenated isoprene tri-block copolymers. Hydrogenated isoprene is ethylene propylene. 

The hydrogenation of the centre block of SBS copolymer produced oxidation stable thermoplastic elastomer. This product was commercialized by the Shell Development Company under the trade name of Kraton G. The field of thermoplastic elastomers based on styrene, 1-3-butadiene or isoprene has expanded so much in the last 10 years that the synthetic rubber chemist produced more of these polymers than the market could handle. However, the anionically prepared thermoplastic system is still the leader in this field, since it produced the best TPR s with the best physical properties. These TPR s can accommodate more filler, which reduces the cost. For example, the SBS Kraton type copolymer varies the monomer of the middle block to produce polyisoprene at various combinations, then, followed... 

The actual temperature acquired by the sample during pyrolysis can be monitored using optical pyrometry or can be standardized between different pyrolyzers using a model compound. The procedure is based on the dependence of the composition of the pyrolysis products on temperature. One such compound chosen as a standard is an isoprene/styrene copolymer, trade name Kraton 1107 [15] (see Section 4.2). 

Using living polymerizations, the Shell Company was able to commercialize several poly(styrene-co-butadiene) and poly(styrene-co-isoprene) block copolymers known in the industry as Kraton 1101 and Kraton G. These block copolymers have found many uses in the shoe sole and adhesive industries. The physical properties were dependent on the macrostructure and microstructure of these block copolymers. 

Figure 1.20 Py-GC-MS chromatogram of Kraton 1107 copolymer (a) isoprene, (b) methyl-benzene, (c) isomers of dimethyl benzene, (d)styrene, (e) 1,4-dimethyl-4-ethenyl-cyclohexene, (f) isopropenyl-benzene and (g) l-methyl-4-(l-methylethenyl)-cyclohexene. Reproduced with permission from M. Statheropoulos, K. Mikedi, N. Tzamtzis and A. Pappa, Analytica Chimica Acta, 2002, 461, 215.

Fig. 14. Comparison of the mechanical properties of tetrafunctional multigraft poly(isoprene-g-styrene) copoljrmers with commercial Styroflex and Kraton copolymers. From Ref. 167.

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