Blends poly styrene/polybutadiene

Joseph, S. Oommen, Z. Thomas, S. Melt elasticity and extrudate characteristics of poly-styrene/polybutadiene blends. Mater. Lett. 2002, 53, 268. 

A preliminary screening indicated that excellent impact could be obtained using 15-20 wt % butadiene based on the total polymer blend. At 20 wt % butadiene, several block polymers were screened for optimum impact and overall balance of properties. Two-component systems (block polymer-polystyrene) and three-component systems (block poly-mer-polybutadiene-polystyrene) were tried. The impact varied with the styrene content of the block polymer in both two- and three-component systems as shown in Figure 1. Subsequent work showed that the best overall balance of impact, flexural modulus, and heat distortion was obtained at 15% butadiene. 

Scalco, Huseby, and Blyler (8), Zosel (9), and Bergen and Morris (10). Prest and Porter (23) applied the same principle to homopolymer blends [poly (2,6-dimethylphenylene oxide)-polystyrene]. Recently some papers were published on triblock copolymers of styrene-butadiene-styrene and on their blends with polybutadiene (24, 25). Triblock copolymers can be considered heterophase material as the different constituent blocks are thermodynamically incompatible with each other, and, consequently, polystyrene domains are enclosed in polybutadiene (continuous matrix). The findings indicate that these systems are in general thermorheologically complex, so that the shift factor ar depends not only on temperature but also on time. These conclusions have been extrapolated to other two-phase systems. 

Other symbols occasionally used in the literature include (br) for branched materials and (iso), (syndio), and (a) for isotactic, syndiotactic, and atactic structures respectively. No symbol appears to exist for mechanical blends, although these materials are obviously important. Where necessary the symbol -m- will denote a mechanical blend, for example, poly(styrene-m-butadiene) for a mechanical blend of polystyrene with polybutadiene. 

In practice, the existence of both UCST and LCST has been established for polymer-solvent systems. About 10 years ago, Schmitt discussed UCST, LCST and combined UCST and LCST behavior in blends of poly(methyl methacrylate) with poly(styrene-co-acrylonitrile) (PMMA-PSAN), Ueda and Karasz reported the existence of UCST in chlorinated polyethylene (CPE) blends using DSC, Inoue found that elastomer blends of cis-l,4-polybutadiene and poly(styrene-co-butadiene) exhibit both UCST and LCST behavior and Cong et al. (72) observed that blends of polystyrene and carboxylated poly(2,6-dimethyl-l,4-phenylene oxide) copolymers with a degree of carboxylation between molar fraction 8% and 10% exhibit both UCST and LCST behavior. They used DSC to establish the phase diagram. 

In the late forties, work began to improve the prcperties of a new thermoplastic blend. It had been revealed [2] in 1948 - 50 that poly(styrene-co-acrylonitrile), or SAN, could be blended with Buna N, a copolymer of butadiene and acrylonitrile, or Buna S, a copolymer of loutadiene and styrene, to get useful thermoplastics. These materials were impact resistant, with Izod impact values of 2 to 3 foot-pounds. The commercial use of these materials was hindered loy the lack of low tenperature impact strength. The rubber technologists of the narbon Division (as the Marsene Corporation had been named on assimilation into Borg-Warner) knew that polybutadiene remained "rubbery" at lower tenperatures than the copolymers cited above. However, blending experiments showed that polybutadiene and SAN were incompatible. The polymerization of SAN could be acconplished in solution, in bulk, or... 

Figure 16.14 LSCM images of poly(styrene-ran-butadiene) and polybutadiene blend imaged at 20(tm beneath the top surface, using (a) reflecting and (b) fluorescence modes ...

Polycarbonate is blended with a number of polymers including PET, PBT, acrylonitrile-butadiene-styrene terpolymer (ABS) rubber, and styrene-maleic anhydride (SMA) copolymer. The blends have lower costs compared to polycarbonate and, in addition, show some property improvement. PET and PBT impart better chemical resistance and processability, ABS imparts improved processability, and SMA imparts better retention of properties on aging at high temperature. Poly(phenylene oxide) blended with high-impact polystyrene (HIPS) (polybutadiene-gra/f-polystyrene) has improved toughness and processability. The impact strength of polyamides is improved by blending with an ethylene copolymer or ABS rubber. 

Cobalt complexes find various applications as additives for polymers. Thus cobalt phthalocyanine acts as a smoke retardant for styrene polymers,31 and the same effect in poly(vinyl chloride) is achieved with Co(acac)2, Co(acac)3, Co203 and CoC03.5 Co(acac)2 in presence of triphenyl phosphite or tri(4-methyl-6- f-butylphenyl) phosphite has been found to act as an antioxidant for polyenes.29 Both cobalt acetate and cobalt naphthenate stabilize polyesters against degradation,73 and the cobalt complex of the benzoic acid derivative (12) (see Section 66.4) acts as an antioxidant for butadiene polymers.46 Stabilization of poly(vinyl chloride)-polybutadiene rubber blends against UV light is provided by cobalt dicyclohexyldithiophosphinate (19).74 Here again, the precise structure does not appear to be known. 

Polyblends with Soft Matrix. Polyblends in which both phases are soft are mixtures of different rubbers. Treads of automobile tires are made of polyblends of SBR with either natural rubber or cts-polybutadiene. Co vulcanization of EPDM with various rubbers is discussed in the chapter of M. E. Woods and T. R. Mass. Relaxation behavior of blends of EVA rubber with styrene/ethylene-butylene/styrene block copolymer and of poly (ethylene oxide) with ethylene oxide/propylene oxide/ethylene oxide block copolymer were studied by M. Shen, U. Mehra, L. Toy, and K. Biliyar. 

All the commercial PBT/PC and PET/PC blends also contain typically 10-20 wt% of an additional elastomeric impact modifier. The exact nature and the content of the impact modifier is kept proprietary and often forms the basis for a particular blend patent. Typically core-shell rubbers such as polymethylmethacrylate grafted butadiene-styrene rubber (MBS) or an all acrylic core-shell rubber such as poly (MMA-g-n-BuA) are used [Nakamura, 1975 Chung, 1985]. ABS (with high polybutadiene content S 50%) or ASA... 

Radioluminescence spectroscopy has been used to examine molecular motion, solubility, and morphology of heterogeneous polymer blends and block copolymers. The molecular processes involved in the origin of luminescence are described for simple blends and for complicated systems with interphases. A relatively miscible blend of polybutadiene (PBD) and poly(butadiene-co-styrene) and an immiscible blend of PBD and EPDM are examined. Selective tagging of one of the polymers with chromophores in combination with a spectral analysis of the light given off at the luminescence maxima gives quantitative information on the solubility of the blend components in each other. Finally, it is possible to substantiate the existence and to measure the volume contribution of an interphase in sty-rene-butadiene-styrene block copolymers. 

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