Kraton copolymers

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

Thermoplastic Elastomers. These represent a whole class of synthetic elastomers, developed siace the 1960s, that ate permanently and reversibly thermoplastic, but behave as cross-linked networks at ambient temperature. One of the first was the triblock copolymer of the polystyrene—polybutadiene—polystyrene type (SheU s Kraton) prepared by anionic polymerization with organoHthium initiator. The stmcture and morphology is shown schematically in Figure 3. The incompatibiHty of the polystyrene and polybutadiene blocks leads to a dispersion of the spherical polystyrene domains (ca 20—30 nm) in the mbbery matrix of polybutadiene. Since each polybutadiene chain is anchored at both ends to a polystyrene domain, a network results. However, at elevated temperatures where the polystyrene softens, the elastomer can be molded like any thermoplastic, yet behaves much like a vulcanized mbber on cooling (see Elastomers, synthetic-thermoplastic elastomers). 

Fig. 20. UV initiated cationic cure of epoxidized block copolymer in the presence of alcohol (Kraton Polymer s EKP-207 and L1203 inono-ol).

An interesting observation arose with the thermoplastic elastomer styrene/ butadiene (S/B) tri-block copolymer (Kraton ). These are made by anionic... 

The pathway and kinetics of the C to S transition have been studied on shear-aligned cylinders of the commercial diblock copolymer of PS and poly(ethylene-co-butylene) (KRATON G 1657 Shell Chemical Company) [143, 144], A complete dissolution of the cylindrical structure before the epitaxial... 

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

Styrene-ethylene-butylene-styrene block copolymer (SEBS) Kraton G, Elexar... 

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. 

The chromatogram of Kraton 1107 shows the other components of the sample besides the major coupled diene S-l-l-S small amounts of "kill" polystyrene, uncoupled S-1 block copolymer, and material with higher molecular weight than that of SlIS are indicated. As indicated in Figures 2a and 3a, the LB polymers all showed a small polystyrene "kill" component and a high molecular weight shoulder on the block copolymer peak with a molecular weight of about twice that of the block copolymer. 

No formal termination is given in structure 5.42 because in the absence of contaminants the product is a stable macroanion. Szwarz named such stable active species living polymers. These macroanions or macrocarbanions have been used to produce block copolymers such as Kraton. Kraton is an ABA block copolymer of styrene (A) and butadiene (B) (structure 5.43). Termination is brought about by addition of water, ethanol, carbon dioxide, or oxygen. 

The most widely used chain reaction block copolymers are those prepared by the addition of a new monomer to a macroanion. AB and ABA block copolymers called Soprene and Kraton, respectively, are produced by the addition of butadiene to styryl macroanions or macrocarbanions (Equation 7.32). This copolymer is normally hydrogenated (Equation 7.33). 

Kraton Trade name for an ABA block copolymer of styrene and butadiene. 

The product obtained by the partial hydrogenation of polybutadiene (Hydropol) has been used as a wire coating and a saturated ABA copolymer (Kraton) is produced by the hydrogenation of the ABA block copolymer of styrene and butadiene. 

Kraton, the yellow rubber-like material often found on the bottom of running shoes, is a copolymer whose structural information is known. It is formed from a group of styrene units, i.e., a block of polystyrene, attached to a group of butadiene units, or a block of... 

Each domain in a block copolymer exhibits its characteristic Ts and Tm. Thus the triblock of styrene-butadiene-styrene (Kraton) has a Tg of 373 K for the styrene block and a Tg of 210 K for the butadiene block. In the temperature range of 210 to 373 K, the block copolymer has both high-resilience and low-creep characteristics. The copolymer is rubbery and flows at temperatures above 373 K. 

The ABA block copolymer of styrene (12.5%)-butadiene (75%)-styrene (12.5%) (Kraton), is a thermoplastic elastomer CTPE) with the multiple repeating units shown below ... 

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... 

HMX HMX HMX HMX HMX HMX HMX HMX HMX HMX HMX HMX HNS NTO NTO/HMX NTO/HMX NTO/HMX PETN PETN PETN PETN PETN PETN PETN PETN PETN PETN RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX TATB/HMX Cariflex (thermoplastic elastomer) Hydroxy-terminated polybutadiene (polyurethane) Hydroxy-terminated polyester Kraton (block copolymer of styrene and ethylene-butylene) Nylon (polyamide) Polyester resin-styrene Polyethylene Polyurethane Poly(vinyl) alcohol Poly(vinyl) butyral resin Teflon (polytetrafluoroethylene) Viton (fluoroelastomer) Teflon (polytetrafluoroethylene) Cariflex (block copolymer of butadiene-styrene) Cariflex (block copolymer of butadiene-styrene) Estane (polyester polyurethane copolymer) Hytemp (thermoplastic elastomer) Butyl rubber with acetyl tributylcitrate Epoxy resin-diethylenetriamine Kraton (block copolymer of styrene and ethylene-butylene) Latex with bis-(2-ethylhexyl adipate) Nylon (polyamide) Polyester and styrene copolymer Poly(ethyl acrylate) with dibutyl phthalate Silicone rubber Viton (fluoroelastomer) Teflon (polytetrafluoroethylene) Epoxy ether Exon (polychlorotrifluoroethylene/vinylidine chloride) Hydroxy-terminated polybutadiene (polyurethane) Kel-F (polychlorotrifluoroethylene) Nylon (polyamide) Nylon and aluminium Nitro-fluoroalkyl epoxides Polyacrylate and paraffin Polyamide resin Polyisobutylene/Teflon (polytetrafluoroethylene) Polyester Polystyrene Teflon (polytetrafluoroethylene) Kraton (block copolymer of styrene and ethylene-butylene)... 

The vinyl monomers used in this study, methacrylic acid, methyl methacrylate, acrylic acid, methyl acrylate, and acrylonitrile, as well as the solvents, initiators, and polystyrene were supplied by the Aldrich Chemical Company. The styrene-butadiene block copolymer was supplied by Shell as Kraton D1102, known as SBS this contains approximately 75% butadiene and 25% styrene. 

Fig, 2.9 (a) TEM micrographs from the hexagonal morphology in Kraton TR1102, a PS-P8-PS block copolymer with fPS 0.24 (Dlugosz el at. 1970 Keller and Odell 1985). 

Fig. 2.61 AFM micrographs of thin films of a Kraton PS-PB-PS triblock copolymer with /pS == 0.24. Part (b) is an enlargement of the square region in part (a), showing the coexistence of regions with parallel and perpendicular cylinders of PS (van Dijk and van den Berg 1995).

A gel permeation chromatogram obtained by Heller (13) indicated that Kraton 101 contained 1% polystyrene, 22% polystyrene/1,4-poly-butadiene, and 77% polystyrene/1,4-polybutadiene/polystyrene, apparently because the material is manufactured by coupling of the diblock. The diblock would be present if the coupling reaction is not 100% efficient. Kraton 101 would thus be essentially a blend of ABBA and AB block copolymers. Assuming that Kraton 102 is manufactured in the same way, the molecular weight of the ABBA block copolymer results as about 72,000 from the above data, the polystyrene blocks having a molecular weight of about 12,000, and the polybutadiene center block one of about 48,000. 

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