Polymer blends with styrene-acrylonitrile

A group of new, fully miscible, polymer blends consisting of various styrene-maleic anhydride terpolymers blended with styrene-acrylonitrile copolymer and rubber-modified versions of these materials have been prepared and investigated. In particular the effects of chemical composition of the components on heat resistance and the miscibility behavior of the blends have been elucidated. Toughness and response to elevated temperature air aging are also examined. Appropriate combinations of the components may be melt blended to provide an enhanced balance of heat resistance, chemical resistance, and toughness. 

Blends with styrene-acrylonitrile copolymer (SAN) 7 represent an important series of systems in which a crystallisable polymer, PCL, is blended with an amorphous (co)polymer. The overall system, with its inherent variations, is complex and provides a good example of situations which can arise generally. These blends have been the subject of a major series of studies which raise many issues which must have a relevance to blends of PCL with other polymers but which have not been addressed in studies of other systems. 

Polypropylene block and graft copolymers are efficient blend compatibilizers. These materials allow the formation of alloys, for example, isotactic polypropylene with styrene-acrylonitrile polymer or polyamides, by enhancing the dispersion of incompatible polymers and improving their interfacial adhesion. Polyolefinic materials of such types afford property synergisms such as improved stiffness combined with greater toughness. 

M. Fowler, J. Barlow, and D. Paul, Effect of copolymer composition on the miscibility of blends of styrene-acrylonitrile copolymers with poly (methyl methacrylate), Polymer, 28(7) 1177-1184, June 1987. 

ABS and Related Materials. The so-called ABS (acrylonitrile-buta-diene-styrene—monomers 1, 2, and 3) materials comprise a class of compounds that consists of either blends or grafts (41). All have three monomers divided between two different polymers in a 1,2 and 1,3 combination mode. Blends of styrene-butadiene (1,2) random copolymers with styrene-acrylonitrile (1,3) random copolymers result in toughened plastics the common-mer, styrene, improves compatibility. The material may be described ... 

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... 

In the early 1980s, workers at Shell could demonstrate melt processability of polyketone produeed by palladium cyanide catalysts, after extensive extraction of catalyst residues from the polymers and blending these with other polymers such as styrene/acrylonitrile copolymer. From these studies, it was suggested that thermoplastic properties were possible in principle, and that the polyketone backbone was not inherently unstable in the melt as previously concluded. However, catalyst extraction did not offer a viable production option from a technical and economic viewpoint. 

The two most important ways of producing ABS polymers are (1) blends of styrene-acrylonitrile copolymers with butadiene-acrylonitrile rubber, and (2) interpolymers of polybutadiene with styrene and acrylonitrile, which is now the most important type. A typical blend would consist of 70 parts styrene-acrylonitrile (70 30) copolymer and 40 parts butadiene-acrylonitrile (65 35) rubber. 

The most common polymers used for instrument panel stmctnres are acrylonitrile-butadiene-styrene (ABS), acrylonitrile-butadiene-styrene blended with polycarbonate (ABS/PC), polycarbonate (PC), poly(phenylene oxide) blended with nylon (PPO/nylon), poly(phenylene oxide) blended with styrene (PPO/styrene), polypropylene (PP), and styrene-maleic anhydride copolymer (SMA) [3]. The percentage of each of these polymers typically used in year 2000 models is shown below in Table 17.3 [3], All of these materials by themselves... 

A material made by blending polymers or copolymers with other polymers or elastomers under selected conditions, e.g., styrene-acrylonitrile copolymer (SAN) blended with butadiene-acrylonitrile elastomer (NBR). A mixture of two chemically different polymers to form a material having properties different from but often comprising those of the original resins. Also see Polymer alloy. Low-molecular-weight polymerization product of allyl monomer, CH2 = CHCH2X, where, for example, X = -OH, -OOCCH3. 

Alloy a- 16i also 9- loi [F aloi, fr. OF alei, fr. aleir to combine, fr. L alligare to bind] (1604) n. A blend of a polymer or copolymer with other polymers or elastomers. An important example is a blend of styrene-acrylonitrile copolymer with butadiene-acrylonitrile rubber. The term polyblend is sometimes used for such mixtures. Some... 

We have already considered blends of PCL with styrene-acrylonitrile copolymers (Sect. 11), which constitutes one of the major studies of PCL blends. In addition, there have been several smaller studies with polystyrene and other styrene-containing polymers which are considered here. 

PS forms a miscible blend with polyxylenyl ether and with tetramethyl bis-phenol polycarbonate. Styrene acrylonitrile (SAN) copolymers can form miscible polymer blends with PMMA over some compositional window of AN and with polyvinyl chloride (PVC). PS and poly(cyclohexyl methacrylate) were reported to... 

Dow has prepared a compatibilized blend of PC and linear PE. The compati-bilizer used was EPDM grafted with SAN. The product has high impact strength and good melt processability. Polymer alloys with S-AMS copolymer and PP with styrene-grafted polyolefin copolymer have been reported. Triax 1000 of Monsanto is a blend of nylon and ABS compatibilized with styrene-acrylonitrile and glycidyl methacrylate terpolymer. The compatibilizer often improves the property balance of an immiscible blend. Reactive compatibilization is an emerging technique. 

Aspects of viscosity, elasticity, and morphology have been discussed in general terms by various workers [73-76]. Rheological studies specific to particular polymers include dynamic rheological measurements and capillary rheometry of rubbers [77], capillary rheometry of PP [78], degradation of PP [79], torsion rheometry of PE [80], viscosity effects in blends of PC with styrene-acrylonitrile and acrylonitrile-butadiene-styrene [81], peel adhesion of rubber-based adhesives [82], and the effect of composition of melamine-formaldehyde resins on rheological properties [83]. 

Isopropanol vapor was used to dissolve the matrix in polymer blends [245]. Williams and Hudson [246] etched microtomed blocks of high impact polystyrene so that the rubber particles protruded from the matrix. Later, Kesskula and Traylor [130] removed rubber particles from Hire and ABS polymers by dissolving the matrix in a cyclohexane solution of osmium tetroxide and extracting the dispersed phase for SEM. Olefin particles were removed from impact modified nylon and polyester [6]. Selective etching of the polycarbonate phase with triethyl-amine in a mixture with styrene-acrylonitrile copolymer (SAN) revealed the nature of the blend [247]. 

In 1946 Naugatuck Chem. Co. introduced i oyaif e, a mechanical blend of styrene-acrylonitrile copolymer, SAN, and NBR, known as ABS-type A [Daly, 1948]. The contemporary version of ABS, so-called ABS-type G, was invented in 1950 by emulsion-grafting of crosslinked polybutadiene particles with styrene and acrylonitrile. The material gained wide application — ABS is a component in about 25% polymer blends. In 1986 these materials constituted 74% of all blends sold in Europe, 77% in Japan, and 69% in North America. 

There are many other commercial examples of polymer blends. Polycarbonate can be blended with an acrylonitrile-butadiene-styrene terpolymer to give a PC-ABS blend. Polypropylene impact can be improved by the addition of ethylene-propylene copolymers, which are sometimes called ethylene-propylene-rubber (EPR). Ethylene, propylene, and a diene monomer (EPDM), such as ethylidene norbomene, is also used to impart impact and flexibiUty to polypropylene. 

Polycaprolactone, which is widely used in medical applications, can be blended with a number of polymers such as styrene-acrylonitrile (SAN), PVC, and polycarbonate. In this example a polymer blend of polycaprolactone with a high nitrile SAN was expected to give a transparent extruded sheet which was thermoformable in hot water. Suitable thermoforming properties and adequate transparency had been achieved with 35 wt% polycaprolactone blended with 65 wt% SAN using small laboratory samples prepared in a torque rheometer. Unfortunately, strips extruded from a pellet blend using a 25 mm laboratory extruder were white, cloudy and not transparent. 

It has, however, been reported that TTS works in some miscible polymer blends with very small difference in the component TgS (Alegria et al. 1995 Friedrich et al. 1996). Figure 7.10 shows the temperature dependence of Oj for PMMA/poly(styrene-co-acrylonitrile) (PSAN) blends and of the constituent components (PMMA and PSAN). It is interesting to observe in Figure 7.10 that the temperature dependence of Y for PMMA is virtually identical to that for PSAN, and that the values of for all blends lie virtually on the same curve as the constituent components. Numerous... 

Acrylonitrile—Butadiene—Styrene. ABS is an important commercial polymer, with numerous apphcations. In the late 1950s, ABS was produced by emulsion grafting of styrene-acrylonitrile copolymers onto polybutadiene latex particles. This method continues to be the basis for a considerable volume of ABS manufacture. More recently, ABS has also been produced by continuous mass and mass-suspension processes (237). The various products may be mechanically blended for optimizing properties and cost. Brittle SAN, toughened by SAN-grafted ethylene—propylene and acrylate mbbets, is used in outdoor apphcations. Flame retardancy of ABS is improved by chlorinated PE and other flame-retarding additives (237). 

Whilst the ASA materials are of European origin, the AES polymers have been developed in Japan and the US. The rubber used is an ethylene-propylene terpolymer rubber of the EPDM type (see Chapter 11) which has a small amount of a diene monomer in the polymerisation recipe. The residual double bonds that exist in the polymer are important in enabling grafting with styrene and acrylonitrile. The blends are claimed to exhibit very good weathering resistance but to be otherwise similar to ABS. 

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