Butadiene block copolymer and its

The Impact Strength of Styrene-Butadiene Block Copolymer and Its Dependence on the Continuous Phase... 

Polystyrene is one of the most widely used thermoplastic materials ranking behind polyolefins and PVC. Owing to their special property profile, styrene polymers are placed between commodity and speciality polymers. Since its commercial introduction in the 1930s until the present day, polystyrene has been subjected to numerous improvements. The main development directions were aimed at copolymerization of styrene with polar comonomers such as acrylonitrile, (meth)acrylates or maleic anhydride, at impact modification with different rubbers or styrene-butadiene block copolymers and at blending with other polymers such as polyphenylene ether (PPE) or polyolefins. 

UV light results in yellowing and embrittlement of SB (styrene-butadiene copolymer) and SBS (styrene-butadiene block copolymer) as it does with other styrene copolymers containing butadiene [83]. Increased hydrophobicity is an important consequence of photo-induced degradation of SBS block copolymers [668]. Therefore, water absorption increases significantly in this material and its mechanical properties decrease considerably as a result. 

Second, the strain-softening phenomenon of a styrene-butadiene-styrene tri-block copolymer and its blend with polystyrene both having alternating lamellar microdomains of the two components i.e., "strain-induced plastic-to-rubber transition" is investigat-d in terms of change of the alternating lamellar microdomains to fragmented sty-... 

When the noncrystallizable block in a diblock copolymer is rubber-like the isotherm shapes are very similar to those of the parent homopolymers.(55,56) This situation exists even when the crystallization occurs from a well-defined melt struc-ture.(55,57,58) However, at a fixed undercooling, there is a reduction in the overall crystallization and spherulite growth rates.(55) When the growth rates of ethylene oxide-butadiene block copolymers, and the corresponding homopolymer, are plotted against l/AT it is found, with the exception of the lowest content ethylene oxide polymer, that a set of parallel straight lines results irrespective of the iiutial melt domain structure.(55) This result implies that the products of interfacial free energies for nucleation are similar to one another. 

In order to obtain the desired photoconductive characteristics, toughness and adherence to the substrate it is usual to incorporate additives such as electron acceptors, plasticisers and primers. A typical electron acceptor is 2,4,7-trinitro-fluoronone, plasticisers include benzyltetraline and phenanthrene whilst as primers styrene-butadiene block copolymers (30-35% styrene) and styrene-maleic anhydride copolymers (5-30% maleic anhydride) are of use. 

Block copolymers such as styrene-butadiene-styrene (SBS) and its hydrogenated versions (SEBS), along with polyester-polyether block copolymers, can also be used to improve PBT impact. The SEBS and SBS copolymers [47], and especially their functionalized, grafted derivatives [48], show surprisingly good affinity for the polyester. 

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. 

In this paper graft copolymerization onto both polystyrene and styrene-butadiene block copolymer will be discussed. It will be shown that radical processes do not permit the addition of monomers onto polystyrene and that one must use anionic initiation in order... 

Of the 17 billion lb of butadiene consumed in 1999, almost two thirds went into the production of elastomers (styrene-butadiene latex rubber (SBR), polybutadiene, nitrile, and polychloroprene). Adiponitrile, ABS resins, styrene-butadiene latex, styrene block copolymers, and other smaller polymer uses accounted for the remainder. The largest single use was for styrene-butadiene copolymers (SBR and latex). Most of it was made by an emulsion process using a free-radical initiator and a styrene-butadiene ratio of about 1 3. More detailed description of the rubber and polymer used can be found in Chapters 16 and 15. 

Besides poly(dimethylsiloxane), other elastomeric polymers have been employed in the manufacturing of vaginal rings, such as poly(dimethylsiloxane/vinylmethylsi-loxane), styrene-butadiene-styrene block copolymer, and poly(ethylene-co-vinyl acetate) [123-125], In fact, poly(ethylene-co-vinyl acetate) (commonly referred as EVA) appeared in the mid 1990s as an alternative to poly(dimethylsiloxane), when the manufacturer of this last material stopped supplying it for human use, demonstrating it to be very suitable for the production of controlled-release systems. 

The use of core-shell impact modifiers combined with styrene-hydrogenated poly butadiene block copolymers in sPS is described by Rohm and Haas [24]. The core of the former type is of polybutadiene or its copolymer, the shell consists predominately of polystyrene. Rohm and Haas found that a synergistic effect is present and that the Izod notched impact strength is higher when both rubber types are used instead of only one. 

Despite the body of patent literature describing fully hydrogenated block copolymers and their properties, it has been suggested that complete saturation of styrenic block copolymers with butadiene would result in materials that were incapable of microphase separation. This argument was based on the supposition that the difference in solubility parameters of the fully saturated block copolymer would be so slight that they would not have useful mechanical properties at achievable molecular weights [58]. This assumption has since... 

Although the model studies indicated that selectivity of sulfonation was considerably less than desired, it was decided to proceed with the synthesis of the polyisoprene/polybutadiene star-block copolymer, anyway. It was felt that selectivity was good enough so that an appreciable fraction of the isoprene units could be sulfonated while limiting sulfonation of the butadiene units to some negligible level. For example, the data in Table II indicates that at 21 C, with a 1 1 mole ratio of sulfonating reagent, one should obtain about 50% sulfonation of the isoprene units with virtually no sulfonation of the butadiene units. This was deemed acceptable since the number of isoprene units at the chain ends could be simply doubled, and... 

Styrenic TPEs are the most widely used. One such material, commercialized by BASE in 1999, is a styrene-butadiene block copolymer with a styrene content of about 70%, intended for thin film for food packaging. It has high oxygen and water permeability, and excellent toughness and optical properties. Cling films with EVA layers on the outside are also available, which provide complete recovery of deformation at elongations up to 400%, and elongation at break of over 650%. 

The melt rheology of amorphous block copolymers, e.g., styrene-butadiene block copolymers (Arnold and Meier, 1968 Holden et al, 1969a Meier, 1969), has been described and interpreted already (Section 4.11). It is interesting to compare the amorphous block copolymers with block copolymers that have the additional feature of crystallizable sequences. A basic study of block copolymer rheology was carried out by Erhardt et al (1970), who determined the complex modulus and tan 6, and studied melt behavior at temperatures between about 60 and 200°C. A report on dielectric behavior by Pochan (1971) is also significant. 

Unlike PAN, this polymer remains unchanged for thermal treatments below 420°C. The use of two types of polymeric matrices permits the study of the influence of the polymer nature on metal particle formation. Co octacarbonyl was chosen for incorporation into polymeric matrices because it can give ferromagnetic cobalt particles in mild thermal conditions however, previously we have found that Co2(CO)g is not compatible with polybutadiene, polystyrene and a pdly(styrene-butadiene) block copolymer. 

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