Styrene/acrylonitrile copolymer blend with poly methyl

Considerable quantities of styrene are used in producing copolymerisates and blends, as, for example, in the production of copolymers with acrylonitrile (SAN), terpolymers from styrene/acrylonitrile/butadiene (ABS polymers) or acrylonitrile/styrene/acrylic ester (ASA), etc. The glass transition temperature of poly (styrene), 100 C, can be increased by copolymerization with a-methyl styrene. What are known as high impact poly (styrenes) are incompatible blends with poly(butadiene) or EPDM, which are consequently not transparent, but translucent. For this reason, pure poly (styrenes) are occasionally called crystal poly (styrenes). 

From studies of styrene-aaylonitrile copolymer (SAN) and poly(methyl methacrylate) (PMMA) blends, Higashida et al. [75] used previously determined values of the interaction parameter between styrene (S) and acrylonitrile (AN) units [76] and phase diagrams of PCL/SAN blends obtained by Chiu and Smith [20] to estimate values of Xs/pcl Xan/pcl functions of temperature and AN content On this basis they calculated phase diagrams similar to that determined experimentally by Chiu and Smith [20]. They also predicted that mixtures of PS and PCL oHgomers should be miscible at low temperatures and that such mixtures should exhibit UCST behaviour which was in agreement with experimental observations values of the interaction parameters determined by Higashida are quoted in Table 4. 

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. 

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 preparing the compatible blend, the compatibilizer is reac-tively blended with PC and a blending partner in the presence of a transesterification catalyst. The blending partner can be a poly(ole-fin), styrene acrylonitrile copolymer, acrylonitrile-butadiene-styrene, poly (methyl methacrylate), or poly (styrene). Suitable transesterification catalysts include tetraphenyl phosphonium benzoate, tetraphenyl phosphonium acetate, and tetraphenyl phosphonium... 

As expected, there are some interesting blends that do not fit the classifications chosen for this chapter and will be summarized in this section. PHE/PVME blends were shown to be miscible with lest behavior observed [ 180]. Partial methylation or benzylation of the secondary hydroxyls of PHE lowered the position of the lest and thus reduced the inherent miscibihty [1140]. PHE was also shown to exhibit miscibility with poly(4-vinyl pyridine), presumably due to the hydrogen bonding potential expected from this combination [223]. The polyformal from the reaction product of tetramethyl Bisphenol S and methylene chloride was foimd to be miscible with styrene-acrylonitrile copolymers (24, 28 and 42 wt% AN) and also poly(vinyl chloride) [1141]. 

Transition from miscibility to immisdbility in blends of poly(methyl methacrylate) and styrene-acrylonitrile copolymers with varying copolymer composition a DSC study. Eur. Polym. J.,... 

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... 

Intramolecular Repulsive Interactions. Miscible blends can also be achieved in absence of specific interactions, by exploiting the so-called intramolecular repulsive effect. This is observed in mixtures where at least one of the components is a statistical copolymer miscibility is restricted to a miscibility window, that is, it takes place within a well-defined range of copolymer composition. For example, poly(styrene-co-acrylonitrile) (SAN) and poly(methyl methacrylate) form miscible blends for copolymer compositions in the range 9-39% acrylonitrile (26,27). Miscibility in these systems is not a result of specific interactions but it is due to the intramolecular repulsive effect (28) between the two monomer units in the copol5uner such that, by mixing with a third component, these imfavorable contacts are minimized. The same situation is encoimtered in binary mixtures of two copol5uners (29). 

Poly(a-methyl styrene) was shown to be miscible with poly(cyclohexyl methacrylate) with /cst behavior [742]. The copolymer of a-methyl styrene and acrylonitrile (31 wt%AN) exhibited miscibility with PMMA when determined by dielectric spectroscopy and calorimetric measurements [743]. The same amS-AN/PMMA blend showed lest behavior and spinodal decomposition phase separation when heated above 180 °C [744]. 

PALS was employed to study the free volume parameters of the binodal and spinodal temperature regimes of poly(a-methyl styrene-acrylonitrile) (50/50 by mole) with a methyl methacrylate-methyl acrylate (95/5 by mole) copolymer [399]. The blend exhibited lest behavior and continuous and step changes were noted at the lest for the binodal and spinodal separation, respectively. The phase separation temperature from PALS showed good agreement with more conventional studies (e.g., TEM, DSC). 

Systems with UCST include polystyrene-poly(methyl methacrylate), and polystyrene-polyisoprene and LCST is found with poly(a-methyl styrene)-poly(methyl methacrylate), poly(styrene-co-acrylonitrile) (SAN)-polycaprolactone and poly(ethylene-co-vinyl acetate)-chlorinated polyethylene [ 5 ] as well as various polyvinylidene fluoride-polyacrylate copolymer blends [35]. 

Poly(vinyl chloride) (PVC) homopolymer is a stiff, rather brittle plastic with a glass temperature of about 80°C. While somewhat more ductile than polystyrene homopolymer, it is still important to blend PVC with elastomer systems to improve toughness. For example, methyl methacrylate-butadiene-styrene (MBS) elastomers can impart impact resistance and also optical clarity (see Section 3.3). ABS resins (see Section 3.1.2) are also frequently employed for this purpose. Another of the more important mechanical blends of elastomeric with plastic resins is based on poly(vinyl chloride) as the plastic component, and random copolymers of butadiene and acrylonitrile (AN) as the elastomer (Matsuo, 1968). On incorporation of this elastomeric phase, PVC, which is ordinarily a stiff, brittle plastic, can be toughened greatly. A nonpolar homopolymer rubber such as polybutadiene (PB) is incompatible with the polar PVC. Indeed, electron microscopy shows... 

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