Polystyrene, copolymers with acrylonitrile-butadiene

The term graft copolymer is used to describe copolymers with long sequences of another monomer (comonomer) as branches on the main polymer chain. Most commercial varieties of high-impact polystyrene (HIP) and copolymers of acrylonitrile, butadiene, and styrene (ABS) are graft copolymen in which the main polymer chain is polybutadiene and the branches are styrene, or styrene and acrylonitrile. Figure 1.12 shows various types of copolymers. 

Order-disorder transitions and spinodals were computed for linear multi block copolymers with differing sequence distributions by Fredrickson et al. (1992). This type of copolymer includes polyurethanes, styrene-butadiene rubber, high impact polystyrene (HIPS) and acrylonitrile-butadiene-styrene (ABS) block copolymers. Thus the theory is applicable to a broad range of industrial thermoplastic elastomers and polyurethanes. The parameter... 

The potential problem of styrene taint in foods is well known and documented in the literature (Saxby 1996). Styrene (see Chapter 2) is the monomer that is polymerized to make polystyrene (PS) (also known as general purpose or GPPS grade). It is also commonly used with butadiene rubber (5-20 % w/w) as a block copolymer to form high impact polystyrene (HIPS). In addition there are less common copolymer grades such as acrylonitrile-butadiene-styrene (ABS) having a mixture of 25 %, 15-25 % and 50-65 % of each monomer respectively or a copolymer with acrylonitrile (styrene-acrylonitrile, SAN). 

The benzene-derived petrochemicals in Figure 4.15 are intermediate feedstocks for styrenic and phenolic plastics. In the styrenics chain, ethylbenzene is dehydrogenated to styrene, to be used as polystyrene monomer or as a copolymer with acrylonitrile and butadiene. In the phenolics chain, cumene is an intermediate for making phenol. Bisphenol A is the condensation product of two moles of phenol and acetone. Phenol and Bisphenol A are used to manufacture resins and polycarbonates. Phenol and cyclohexane are the starting materials for the manufacture of nylon 6. 

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. 

Transparent and brittle used for cheap molded objects, e.g., Styron, Carinex, Hostyren, Lustrex. Modified with rubber to improve toughness, e.g., High impact Polystyrene (HIPS) and acrylonitrile-butadiene-styrene copolymer (ABS). Expanded by volatilization of a blended blowing agent (e.g., pentane) to make polystyrene foam, e.g., Styrocell, Styrofoam... 

Oligomeric aromatic phosphates have been patented and commercially used as flame-retardant additives mainly for impact-resistant polystyrene blends with polyphenylene oxide and polycarbonate blends with acrylonitrile-butadiene-styrene (ABS) copolymers (130,131). They have also been shown useful in thermoplastic polyesters (92). The principal commercial examples are based on phenol and resorcinol (Akzo-Nobel s Fyrolflex RDP) or phenol and bisphenol A (Akzo-Nobel s Fyrolflex BDP or Albemarle s Ncendx P-30). Although these have the diphosphate as their principal ingredient, they also contain higher oligomers. 

The products based on starch/EVOH show mechanical properties good enough to meet the needs of specific industrial applications (133). Their moldabil-ity is comparable with that of traditional plastics such as polystyrene (PS) and acrylonitrile-butadiene-styrene copolymer (ABS). Nevertheless, they continue to be highly sensitive to low humidities, especially when in film form, with evident embrittlement. 

Another polyolefin of interest is polystyrene, a clear, brittle plastic that, by itself, is rarely used in composites. However, several copolymers and alloys of polystyrene with acrylonitrile or butadiene have been used with fiber glass or glass spheres to form composites (7). 

We have considerable latitude when it comes to choosing the chemical composition of rubber toughened polystyrene. Suitable unsaturated rubbers include styrene-butadiene copolymers, cis 1,4 polybutadiene, and ethylene-propylene-diene copolymers. Acrylonitrile-butadiene-styrene is a more complex type of block copolymer. It is made by swelling polybutadiene with styrene and acrylonitrile, then initiating copolymerization. This typically takes place in an emulsion polymerization process. 

The isoprene units in the copolymer impart the ability to crosslink the product. Polystyrene is far too rigid to be used as an elastomer but styrene copolymers with 1,3-butadiene (SBR rubber) are quite flexible and rubbery. Polyethylene is a crystalline plastic while ethylene-propylene copolymers and terpolymers of ethylene, propylene and diene (e.g., dicyclopentadiene, hexa-1,4-diene, 2-ethylidenenorborn-5-ene) are elastomers (EPR and EPDM rubbers). Nitrile or NBR rubber is a copolymer of acrylonitrile and 1,3-butadiene. Vinylidene fluoride-chlorotrifluoroethylene and olefin-acrylic ester copolymers and 1,3-butadiene-styrene-vinyl pyridine terpolymer are examples of specialty elastomers. 

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. 

Copolymerization allows the synthesis of an almost unlimited number of different products by variations in the nature and relative amounts of the two monomer units in the copolymer product. A prime example of the versatility of the copolymerization process is the case of polystyrene. More than 11 billion pounds per year of polystyrene products are produced annually in the United States. Only about one-third of the total is styrene homopolymer. Polystyrene is a brittle plastic with low impact strength and low solvent resistance (Sec. 3-14b). Copolymerization as well as blending greatly increase the usefulness of polystyrene. Styrene copolymers and blends of copolymers are useful not only as plastics but also as elastomers. Thus copolymerization of styrene with acrylonitrile leads to increased impact and solvent resistance, while copolymerization with 1,3-butadiene leads to elastomeric properties. Combinations of styrene, acrylonitrile, and 1,3-butadiene improve all three properties simultaneously. This and other technological applications of copolymerization are discussed further in Sec. 6-8. 

Note-. 2 - sufficient thermal stability and limited reactivity with polymer allows broad use, 1 = marginal thermal stability or potential reactivity with polymer restricts use, 0 = generally unsuitable for use. FPVC, Flexible Polyvinyl Chloride RPVC, Rigid Polyvinyl Chloride PS, Polystyrene LDPE, Low Density Polyethylene HDPE, High Density Polyethylene PP, Polypropylene ABS, Acrylonitrile-butadiene-styrene copolymer PET, Polyethylene terephthalate PA, Polyamide PC, Polycarbonate... 

In works [46-48] by method of EPR-tomography thermo- and photo-oxidation of poly(acrylonitrile-butadiene)styrene (ABS) copolymer were studied. This polymer is structurally and dynamically micro-heterogeneous, i.e. there are regions with high content of polybutadiene and regions with high content of polystyrene or polyacrylonitrile. In polymer... 

MABS polymers (methyl methacrylate-acrylonitrile-butadiene-styrene) together with blends composed of polyphenylene ether and impact-resistant polystyrene (PPE/PS-I) also form part of the styrenic copolymer product range. Figure 2.1 provides an overview of the different classes of products and trade names. A characteristic property is their amorphous nature, i.e. high dimensional stability and largely constant mechanical properties to just below the glass transition temperature, Tg. 

There are a number of flame-retardant styrenic polymers that will be covered in this chapter. These include polystyrene itself, rubber-modified polystyrene [high-impact polystyrene (HIPS)] and rubber-modified styrene-acrylonitrile copolymer [acrylonitrile-butadiene-styrene (ABS)]. Blends with styrenic... 

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