Blends SMMAs

Fig. 6. Miscibility doors of PVME/SMMA blends having different blend ratios ( ) 80/20, ( ) 50/50, (A) 35/65, ( ) 20/80 [36]...

Ill 50/50 blends of SAN and SMMA at room temperature one phase, O two phases. The solid and dashed curves were calculated as in II [6]. 

Similar miscibility maps were reported for 50/50 blends of SMMA and poly(S-ran-maleic anhydride) (SMA) [6]... 

IV 50/50 blends of SMMA and MMA-MA two phases. The solid curve is calculated for a degree of polymerization of 500. Both components are miscible in the area above the curve [7]. 

There are a wide range of applications that are made from SBC that may show up in the ordinary household. Some SBCs are used in appliances, housewares and office supplies. Owing to limitations of temperature resistance, chemical resistance, and abrasion resistance, the SBC may be blended with polymers such as styrene-methyl methacrylate (SMMA) to improve functionality. SBCs may also be seen in parts such as aquarium filter tanks, sewing machine dust covers, bird feeders, cake pan lids, pens, vacuum cleaners and computer accessories. 

Another polymer that has been very successful in blends with SBC is polystyrene-methyl methacrylate (SMMA), a styrene acrylic copolymer. Compared with SBC, SMMA offers significantly higher stiffness, surface hardness and temperature resistance. The refractive index of these copolymers can be... 

SMMA blends can also be used in extruded sheet and profile extrusion. Depending on the styrene-acrylic copolymer, its blend level and the processing conditions, the clarity of extruded parts may not be as good as the clarity of injection molded parts. 

New grades of SMMA are being developed that have shown tremendous potential for blends in SBC. These new grades result in very high impact in the blends with higher loadings of SMMA. Notched Izod impact values of almost 5 ft-lb/in have been reported for injection molded test specimens containing 50 % SMMA [22]. 

In 1983, Monsanto developed blends with co-continuous morphology, Triax 2000. These alloys comprised PC, ABS, and styrene-methylmethac-rylate-maleic anhydride (SMMA-MA) [Jones and Mendelson, 1985]. One year later, PC was reactively blended with either ABS, SAN-GMA, and NBR, or with graft copolymers of acrylonitrile-butadiene-a-methyl styrene-methyl-methacrylate (MeABS) and acryloiutrile-a-methyl styrene-methyl methacrylate copolymer (MeSAN) [Kress et al., 1986]. The blends were commercialized by Bayer as Bayblend . 

In the 1950 s, the core-shell, emulsion type methylmethacrylate-butadiene-styrene terpolymer (MBS) was developed to toughen PVC or PC. These blends could also contain other polymers, viz. SAA [Murdock et al., I960] SMM and PS [Murdock et al., 1962] SMM-AN [Schmitt et al., 1967] high heat ABS [Kanegafuchi Chemical Industry, 1967] HIPS [Ward, 1970] MMVAc-AA [Holland et al., 1970] SMMA [Blasius, 1992], etc. Table 1.34 traces evolution of these systems. Later, these multipolymers were modified by incorporation MA, AA, or GMA units to serve as reactive compatibilizers and toughening agents for PA, PEST or PC blends. 

PPE, with SAN, SMMA, SAA or SMA Miscibility of copolymers with PPE when the amount of comonomer is small. The interfacial energy between the blend components was significantly reduced by adding either a PS-b-PMMA, or PS-b-PEB-b-PMMA. The copolymers had a profound influence on morphology, phase adhesion and mechanical properties of the blend. Gottschalk et al., 1994... 

SAN/SMMA/MAN Ternary blends prepared in THF, precipitated by MeOH, then dried DSC at 20 °C/min over T = 310-430 K 7... 

PA-6 (20 parts)/PPE (60 parts)/ SMA (20 parts) TSE at 280 °C/PA preextruded with SMA/mechanical properties vs. blends with either PS or SMMA copolymer/also used SMMA-MA or styrene-N-phenyl maleimide copolymer Kasahara et al. 1982... 

Although the unmodified styrenics, viz., polystyrene, SAN, SMA, SMMA copolymers, exhibit good clarity, strength, and rigidity, they are invariably brittle for many applications. Hence, the rubber-modified styrenics such as HIPS and ABS, which combine a good level of impact strength with moderate heat resistance, have become more widely accepted in many molding and extrusion applications. Structurally, HIPS and ABS may themselves be considered as blends, since they contain >5 % polybutadiene rubber as a discrete phase, dispersed as 0.1-5 pm-size... 

Another promising area of growth is for SBC blends with higher-performing styrenics such as styrene-methyl methacrylate (SMMA) and SAN, in order to down-engineer applications currently in higher-cost PC, acrylic, or clear ABS. Potential uses include molded appliance parts and medical devices and extruded graphic display profiles. 

Homogeneous blends of a thermoplastic styrene/methyl methacrylate (SMMA) copolymer and a thermoplastic vinylidene fluo-ride/hexafluoropropylene copolymer which is an excellent processing additive for the extrusion of thermoplastic polyolefin (1). 

The window of miscibility in this case is an ellipse contained within the boundaries of the copolymer composition map. Additional examples of the mean field approach to predict the miscibility window for cop olymer-copolymer blends include SAN/SMMA, SMMA/MMA-AN and SAN/MMA-AN [188], amSAN/SAN and amSAN/SMA [202], SMMA/SMMA (different compositions) [203 ], SMA/tetramethyl Bis A polycarbonate [204], chlorinated PVC (different compositions), chlorinated polyethylene (different compositions and MMA-EMA (different compositions) [177] and SAN/NBR [205]. This approach has also been applied to ternary blends of PPO/PS/poly(o-chlorostyrene-co-p-chlorostyrene) [206]. The mean field binary interaction model approach was also successfully applied to polyamides based on various combinations of aliphatic and aromatic units [207]. 

Polystyrene is immiscible with PC however, tetramethyl Bisphenol A polycarbonate (TMPC) is miscible and exhibits lest behavior [439]. The CPMAS NMR analysis gave indication of homogeneity of the TMPC/PS blend at the level of a few nanometers [440], consistent with SANS data of 2 nm [441]. Styrene-MMA copolymers are immiscible with PC, but miscible with TMPC [442]. Miscibility maps for SMMA copolymer blends with hexafluorobisphenol A-tetramethyl bisphenol A copolymers show areas of single phase behavior. TMPC miscibility windows with a series of styrene copolymers (SAN, SMA, styrene-allyl alcohol (SAAl)) have been reported [443 ]. Miscibility of the copolymers with TMPC was maintained for SAN (0-13 wt% AN), SMA (0-8 wt% MA) and SAAl (0-19 wt% aUyl alcohol). Dimethyl bisphenol A-tetramethyl bisphenol A PC copolymer blends with SMMA yielded miscibility with SMMA (< 37 wt%) and PC copolymer with > 60 wt% tetramethyl bisphenol A content [444]. Tetramethyl Bisphenol S polycarbonate is not miscible with polystyrene, but is miscible with styrene-acrylonitrile copolymers (range estimated to be 14 to 42 wt% AN) [445]. Miscibility was also observed with an a-methyl styrene-acrylonitrile copolymer (31 wt% AN). 

The miscibility mapping of SMA copolymers with SAN and SMMA copolymers was determined by Gan and Paul [740], showing significant miscible composition ranges as illustrated in Figs. 4.23 and 4.24 for the SMA/SMMA and SMA/SAN blends. Two set of B,j values were employed to fit the experimental observations as noted in the figures. The spinodal decomposition of miscible blends of SMA (32 wt% MA) and a MMA-EA (10 wt%EA) copolymer was studied, showing a lest minimum at 190 °C [741]. 

Styrene-acryhc acid (SAA) copolymers have been noted in Section 4.4.1 to exhibit miscibility with polyamides. Miscibility has also been observed with SAA and various polymethacrylates (PMMA, PEMA, PnPMA) at low AA content in SAA [745]. The miscibility window of SAA with SMMA copolymers was defined, showing a narrow miscibility range as a function of AA and MMA in the respective copolymers. The miscibility was explained using the mean field approach (copolymer repulsion mechanism). Similar results were reported for SAA copolymer blends with PEMA, with immiscibility for SAA with poly(isobutyl methacrylate) [746]. Ckjpolymerization of isobutyl methacrylate with 4-vinyl pyridine yielded miscible compositions with SAA, as would be expected based on the strong specific interaction. 

Figure4.23 Miscibility map for 50/50 (by wt) SMA/SMMA blends (reproduced from Gan P.P.and Paul.D. R.J.Appl. Polym.Sci. (1994) 54, p. 317 with permission of John Wiley Sons, Inc.)...

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