Compatibility, poly -polystyrene blends

Addition of AN to a level of 40% (NBR-40) destroys the phase boundaries entirely, resulting in the microheterogeneous system shown in Figure 3.10. The phase domains ( 100 A) shown in Figure 3.10 are clearly smaller than the polymer molecules themselves, yet the material is not totally compatible. Only a few cases are known in which the phase division in blends is so fine such cases include the IPN s discussed in Chapter 8 and the poly(2,6-dimethyl phenylene oxide)/polystyrene blend described in Section 9.7.1. 

In this paper, an attempt is made to relate the mechanical (tensile) properties of a family of related polyblends to the state of compatibility of the blend. The prototype compatible blend studied is that of poly (2,6-dimethy1-1, 4-phenylene oxide)(PPO) and polystyrene (PS). Evidence for the compatibility of PPO and PS is substantial and is reviewed elsewhere (5). Films molded from blends of PPO and PS are optically clear and exhibit a single composition dependent glass transition temperature (Tg). 

Blends of poly(methacrylic acid) or polystyrene with epoxidised linseed oil are prepared in solution by mechanical mixing in dimethyl sulphoxide (DMSO) or tetrahydrofuran (THF) to improve the performance of the individual components. However, blends of poly(methylacrylic acid) are not able to produce compatible systems, although different compositions (15-55 wt%) of polystyrene blends will form miscible blends. The results show an improvement in properties, including biodegradation of the miscible blends, and the systems are comparable with low density polyethylene. 

Brekner, M,( Cantow, H.J., and Schneider, H,A, (1985) Interactions in compatible polymer systems - 1. Viscoelasticity and ass transition of polystyrene-poly(vinylmethylether) blends, Pdlym. BuU., 14 (1), 17-24. 

These interaction parameters were determined in order to establish the compatibility of polymer blends and of chains of block copolymers. There are also determinations for blends poly(vinylchloride)-poly-e-caprolactone [27], polystyrene-poly (vinyl methyl ether) [28], polystyrene--polydimethylsiloxane above (120—180°0) and below (50—80°0) the glass... 

As noted earlier, the first major engineering polymer blend was poly(2,6 dimethyl-1,4-phenylene oxide) (PPO) with impact polystyrene. PPO and polystyrene exhibit miscibility over the entire composition range and thus mechanical compatibility. PPO/impact polystyrene blends were commercialized by General Electric in the late 1960s [52, 53] under the trade-... 

As of now, theory is inadequate to make safe predictions concerning polymer miscibility. It has been suggested (15) that hydrogen bonding is responsible for the compatibility of poly(vinyl chloride) with polycaprolactone and the decrease in the carbonyl stretching frequency (16) is consistent with this interpretation. To account for the compatibility of polystyrene with poly(3,5-dimethvl p-phenylene oxide) is more difficult it may be due to an increasing packing efficiency in the blend (17). 

Poly [bis (p-chlorophenoxy)phosphazene]— Polystyrene Blends Preparation, Compatibility, and Properties... 

The heat distortion temperature of impact-resistant polystyrene may also be improved by polymer blends. Those of impact-resistant polystyrene with poly-2,5-dimethylphenylene-1,4-oxide (PPO) are particularly interesting (90). Polystyrene and PPO are molecularly compatible and mixtures of them have glass transition temperatures which vary virtually linearly with composition. A further advantage of these compositions which should not be under-estimated is their better flame resistance. 

The ionic aggregates present in an ionomer act as physical crosslinks and drastically change the polymer properties. The blending of two ionomers enhances the compatibility via ion-ion interaction. The compatibilisation of polymer blends by specific ion-dipole and ion-ion interactions has recently received wide attention [93-96]. FT-IR spectroscopy is a powerful technique for investigating such specific interactions [97-99] in an ionic blend made from the acid form of sulfonated polystyrene and poly[(ethyl acrylate - CO (4, vinyl pyridine)]. Datta and co-workers [98] characterised blends of zinc oxide-neutralised maleated EPDM (m-EPDM) and zinc salt of an ethylene-methacrylic acid copolymer (Zn-EMA), wherein Zn-EMA content does not exceed 50% by weight. The blend behaves as an ionic thermoplastic elastomer (ITPE). Blends (Z0, Z5 and Z10) were prepared according to the following formulations [98] ... 

Figure 1. Room-temperature miscibility diagrams for blends of polystyrene with poly(methyl methacrylate) and styrene/(methyl methacrylate) copolymers. Shaded area is compatible region.

On the other hand, some mechanically compatible blends as well as some dispersed two-phase systems have made respectable inroads into the commercial scene. Many of these are blends of low-impact resins with high-impact elastomeric polymers examples are polystyrene/rubber, poly (styrene-co-acrylonitrile) /rubber, poly (methyl methacrylate) /rubber, poly (ethylene propylene)/propylene rubber, and bis-A polycarbonate/ ABS as well as blends of polyvinyl chloride with ABS or PMMA or chlorinated polyethylene. 

As reported by Diehl et al. [58], interpolymers are also compatible with a broader range of polymers, including styrene block copolymers [59], poly(vinyl chloride) (PVC)-based polymers [60], poly(phenylene ethers) [61] and olefinic polymers such as ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer and chlorinated polyethylene. Owing to their unique molecular structure, specific ESI have been demonstrated as effective blend compatibilizers for polystyrene-polyethylene blends [62,63]. The development of the miscibility/ compatibility behavior of ESI-ESI blends differing in styrene content will be highlighted below. 

Compatible Polyblends. When the polymeric materials are compatible in all ratios, and/or all are soluble in each other, they are generally termed polyalloys. Very few pairs of polymers are completely compatible. The best known example is the polyblend of polyCphenylene oxide) (poly-2,6-dimethyl-l,4-phenylene oxide) with high-impact polystyrene (41). which is sold under the trade name of Noryl. It is believed that the two polymers have essentially identical solubility parameters. Other examples include blends of amorphous polycaprolactone with poly(vinyl chloride) (PVC) and butadiene/acrylonitrile rubber with PVC the compatibility is a result of the "acid-base" interaction between the polar substituents (1 ). These compatible blends exhibit physical properties that are intermediate to those of the components. 

Polyblends in which both phases are rigid are frequently called poly alloys. Poly (phenyl oxide) is blended with impact polystyrene to improve melt flow. Complete compatibility between the two phases is rare and was observed between poly (methyl methacrylate) and poly(vinylidene fluoride) by D. R. Paul and J. O. Altamirano. Thermoplastics are added to polyesters to reduce mold shrinkage. 

Blends of polystyrene(PS) and poly(vinyl methyl ether) (PVME) have attracted much interest because of their compatibility over a wide range of blend composition . The compatibility of PVME with styrenic copolymers has also been extensively investigated. 

Polystyrene (PS) and poly(vinylmethylether)(PVME) are mutually compatible over the entire range of composition, and their blends have thus often been chosen for experimental studies on the phase separation dynamics of binary polymer mixtures. The subsequent discussion depends heavily on the data re-... 

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