Kraton G

Hydrogenated SBS triblock polymers have become increasingly important (Kraton G by Shell). With the original polybutadiene block comprised of 65% 1,4-and 35% 1,2-structures the elastomeric central block is equivalent to that of a high-ethylene ethylene-butene rubber. 

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... 

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

Elexar, C-Flex, Tekron, Hercuprene, Kraton G, Septon, Dynaflex, and Multi-Flex. 

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 NTO/TNT formulation is characterized by a lower vulnerability than RDX/ TNT and Composition B. NTO is also used to produce pressed PBXs with thermoplastic binders and cast PBXs with thermosetting binders for IMs. NTO is an explosive with calculated performance near that of RDX but with insensitivity approaching that of TATB. Possible use of NTO is as an alternative to RDX in formulations where a lower sensitivity is desired or as an alternative to TATB where better performance is required without a large increase in sensitivity [123, 152, 153, 215]. The formulations based on NTO/binder (FPC-461, Viton-A, Kel-F800, Estane-5702 and Kraton G) in 95/5 (mass percent concentrations) have also been tested for compatibility and none of the NTO/binder formulations showed evidence of incompatibility. 

Formulation component Kraton G1650, 65 parts Kraton G 1657, 35 parts Neville LX-685,60 parts Piccofyn A-l 35, 60 parts Picovar AB165,65 parts zircoaluminate, 4-6 parts. 

Kraton D SBS Kraton D SIS Kraton G Kraton FG Kraton IR Kraton IR Latex... 

Amphiphilic copolymers have been prepared that have reduced surface contact angles and are effective as emulsifying agents or absorbents. These materials were prepared by reacting poly[styrene-b-poly(ethylene-butylene)-g-succinic anhydride-b-polysty-rene)] [Kraton G 1901 ] with methoxypolyethylene glycols having M s between 2000 and 8000 daltons. 

Table 19.2 Notched impact strength (ak) of styrene polymers with 35% Kraton G 1651 under different processing procedures (Inj.m. = injection moulded)...

Figure 19.13 shows the dynamic mechanical properties of such a blend of sPS with a mixture of Kraton G 1651 (15 %) and microsuspension rubber particles (20%) consisting of 60% butyl acrylate (BA) core grafted with 40% styrene shell (S//BA). The glass transition temperatures of the Kraton (-60 °C) and the butyl acrylate (-45 °C) phases can be easily distinguished from one another. The TEM image of such a product after deformation is shown in Figure 19.14. The annealed specimen is shown since the two rubber types are better discernible than in the nonannealed sample. As expected, crazing and voiding in the rubber particles dominate. The product had the following notched impact strengths (ISO 179/eA) injection moulded (80 °C mould temperature) 6.3, injection moulded (140 °C) 4.0 and annealed 3.7kJ/m2.

Figure 19.13 Dynamic shear modulus (cycles/s) of sPS, rubber modified with a mixture of 15 % Kraton G 1651 and 20 % S//BA particles produced in microsuspension...

Obviously, the resistance of these products towards light, oxygen and other chemicals will be much better, and close to that of the corresponding polyolefins. Moreover, the hydrogenation can be stopped at different conversions opening a much broader range of applications conditions. Industrial developments already include successful materials like Kraton G thermoplastic elastomers. 

Figure 2. Scanning electron micrographs of a blend with 5% Kraton G—1652M that was drawn to fracture and cryogenically fractured lengthwise. The direction of stress is shown by the arrow.

Microfibrils in the blend compatibilized with Kraton G probably formed by drawing of the rubbery shell of the core-shell particle. Important factors would have been the amount of rubber in the shell, the strength of the rubber, and the strength of adhesion to LLDPE. All these factors may have contributed in some degree to the high fracture stress and strain of the blend with Kraton G. The amount of compatibilizer in the shell differed for the various Kratons the thicker coating was certainly one of the reasons Kraton G gave better properties to the compatibilized blend than the Kraton D compatibiliz-ers. 

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