Acrylonitrile-butadiene-styrene dispersion

Rubber-Modified Copolymers. Acrylonitrile—butadiene—styrene polymers have become important commercial products since the mid-1950s. The development and properties of ABS polymers have been discussed in detail (76) (see Acrylonitrile polymers). ABS polymers, like HIPS, are two-phase systems in which the elastomer component is dispersed in the rigid SAN copolymer matrix. The electron photomicrographs in Figure 6 show the difference in morphology of mass vs emulsion ABS polymers. The differences in stmcture of the dispersed phases are primarily a result of differences in production processes, types of mbber used, and variation in mbber concentrations. 

Acrylonitrile-Butadiene-Styrene (ABS) Copolymers. This basic three-monomer system can be tailored to yield resins with a variety of properties. Acrylonitrile contributes heat resistance, high strength, and chemical resistance. Butadiene contributes impact strength, toughness, and retention of low-temperature properties. Styrene contributes gloss, processibility, and rigidity. ABS polymers are composed of discrete polybutadiene particles grafted with the styrene-acrylonitrile copolymer these are dispersed in the continuous matrix of the copolymer. 

Various patents on the homopolymerization of BD in the presence of styrene are available [581-590]. According to these patents, St is used as a solvent in which BD is selectively polymerized by the application of NdV/DIBAH/EASC. At the end of the polymerization a solution of BR in St is obtained. In subsequent reaction steps the unreacted styrene monomer is either polymerized radically, or acrylonitrile is added prior to radical initiation. During the subsequent radical polymerization styrene or styrene/acrylonitrile, respectively, are polymerized and ris-l,4-BR is grafted and partially crosslinked. In this way BR modified (or impact modified) thermoplast blends are obtained. In these blends BR particles are dispersed either in poly(styrene) (yielding HIPS = high impact poly(styrene) or in styrene-acrylonitrile-copolymers (yielding ABS = acrylonitrile/butadiene/ styrene-terpolymers). In comparison with the classical bulk processes for HIPS and ABS, this new technology allows for considerable cost reductions... 

Grafted Rubber Latex Particles as the Disperse Phase. ABS polymers or acrylonitrile-butadiene-styrene polymers, can be generally made by piggy-back grafting of a polybutadiene latex with styrene and... 

Co-continuous polymer blends of 50/50 polyamide6/acrylonitrile-butadiene-styrene copolymer (PA6/ABS) involving multiwall carbon nanotubes (MWNTs) were prepared by melt mixing technique in order to develop conducting composites utilizing the concept of double-percolation. To control the dispersion and to selectively restrict MWNTs in the PA6 phase of the blends, MWNTs were pre-treated with two modifiers which differ in their molecular length scales and... 

After the examination of the PS photooxidation mechanism, a comparison of the photochemical behavior of PS with that of some of its copolymers and blends is reported in this chapter. The copolymers studied include styrene-stat-acrylo-nitrile (SAN) and acrylonitrile-butadiene-styrene (ABS). The blends studied are AES (acrylonitrile-EPDM-styrene) (EPDM = ethylene-propylene-diene-monomer) and a blend of poly(vinyl methyl ether) (PVME) and PS (PVME-PS). The components of the copolymers are chemically bonded. In the case of the blends, PS and one or more polymers are mixed. The copolymers or the blends can be homogeneous (miscible components) or phase separated. The potential interactions occurring during the photodegradation of the various components may be different if they are chemically bonded or not, homogeneously dispersed or spatially separated. Another important aspect is the nature, the proportions and the behavior towards the photooxidation of the components added to PS. How will a component which is less or more photodegradable than PS influence the degradation of the copolymer or the blend We show in this chapter how the... 

In rubber-modified polymers like high impact polystyrene or acrylonitrile-butadiene-styrene (ABS) resins, the toughening effect of the dispersed rubber particles appears only in the presence of block or graft copolymers. These copolymers regulate the particle size of the rubber dispersion and achieve adhesion of the two phases. Hence, graft copolymers are of practical importance in polymer alloys. 

In heterophase polymeric materials such as rubber modified polystyrene or acrylonitrile-butadiene-styrene (ABS) resins, outstanding mechanical properties can be obtained only by regulating the dispersed rubber particle size and by achieving adhesion between the rubber and the resin phase. This can usually be achieved by adding block or graft copolymers, or by their formation in situ, as in industry. 

HIPS) is produced commercially by the emulsion polymerization of styrene monomer containing dispersed particles of polybutadiene or styrene-butadiene (SBR) latex. The resulting product consists of a glassy polystyrene matrix in which small domains of polybutadiene are dispersed. The impact strength of HIPS depends on the size, concentration, and distribution of the polybutadiene particles. It is influenced by the stereochemistry of polybutadiene, with low vinyl contents and 36% d5-l,4-polybutadiene providing optimal properties. Copolymers of styrene and maleic anhydride exhibit improved heat distortion temperature, while its copolymer with acrylonitrile, SAN — typically 76% styrene, 24% acrylonitrile — shows enhanced strength and chemical resistance. The improvement in the properties of polystyrene in the form of acrylonitrile-butadiene-styrene terpolymer (ABS) is discussed in Section VILA. 

Many thermoplastics are heterogeneous (or heterophase) because they contain liquid or rubber dispersions that improve their physical properties with respect to those of the continuous brittle phase. Examples of this are the softening of PVC by the presence of phthalate droplets and the improved toughness of HIPS or the polymer of acrylonitrile-butadiene-styrene (ABS) by addition of PBD-based rubber particles. This chapter will focus on the (heterogeneous, bulk and free-radical) polymerizations leading to the production of HIPS and PVC. 

High-impact polystyrene and acrylonitrile-butadiene-styrene copolymer are often prepared in a combined bulk-suspension process. This begins with a solution of polybutadiene in styrene or styrene/acrylonitrile. Subsequently, the polymerization of styrene or styrene/acrylonitrile is initiated and continues under stirring until phase inversion occurs (i.e., polybutadiene is dispersed in a continuous PS matrix - Chapter 4). In the final stage, water and dispersant are added to the system and the polymerization is completed in suspension. 

A substantial part of the synthetic polymer dispersions is commercialized as dry products. These include styrene-butadiene rubber (SBR) for tires, nitrile rubbers, about 10% of the total poly(vinyl chloride) production, 75% of the total acrylonitrile-butadiene-styrene... 

To achieve more uniform nanotube dispersion in composites, Haggenmueller et al. [59] developed an alternative melt mixing method consisting of a combined solution-evaporation technique to prepare a thin SWNT-polymer film followed by repeated compression molding of the latter. The resulting product was reported to yield compositionally uniform films. Using a small batch mixer, adequately dispersed nanotube composites from polypropylene, poly(acrylonitrile-butadiene-styrene), polystyrene, and high impact polystyrene have been prepared [60]. 

Figure 9.18 Transmission electron microscopy images of three different acrylonitrile-butadiene-styrene (ABS) terpolymers, showing a continuous phase of styrene-co-acrylonitrile and a dispersed phase of butadiene, corresponding to the dark phase on images.

Table 6 Recipe for the preparation of acrylonitrile-butadiene-styrene (ABS) dispersion by emulsion polymerisation at 50 °C ...

Impact Modifiers Impact modifiers are either systems with spherical elastomer particles in a rigid polymer matrix or they are systems with a honeycomb, network type of dispersed elastomeric phase. For the spherical elastomeric particles, examples are acrylonitrile butadiene styrene (ABS), methacrylate-butadiene-styrene (MBS) and acrylics. These systems are either graft copolymers of methyl methacrylate-butyl acrylate-styrene or methyl methacrylate-ethylhexyl acrylate-styrene. For the honeycomb, network type of dispersed elastomeric phase ethylene vinyl acetate (EVA) and chlorinated polyethylene (CPE) or directly dispersed rubber are examples. Both of these two impact modifiers exist in the polymeric form, hence they can hardly migrate and evaporate because of their size. As a result, they pose almost no problems to health. For PVC window frame production, usually the first type (and acrylic impact modifiers) are used while MBS modifiers are found to be very effective in plasticised as well as in rigid PVC. CPE is mainly used in PVC for products like sheet, pipe, gutters and sidings. 

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