Blends of Syndiotactic Polystyrene with Polystyrenes

TOMOAKI TAKEBE, KOMEI YAMASAKI, AKIHIKO OKADA, and TAKUMA AO YAM A-  

So far, the tacticity effect on polymer mixtures has been investigated mainly for the special systems where hydrogen bonding interaction is dominant, such as poly (vinyl chloride)/poly(methyl metacrylate) (PVC/PMMA) [1] or poly-styrene/poly(vinyl methyl ether) (PS/PVME) [2] mixtures. However, recently, there has been an interest in the effect of tacticity on polymer mixtures without specific interaction such as polyolefin/polyolefin [3] or polystyrene/ deuterated polystyrene mixtures [4,5]. 

Syndiotactic Polystyrene, Edited by Jurgen Schellenberg Copyright 2010 John Wiley Sons, Inc. 

This section presents the evaluation of the segmental interaction of polystyrene blends with different tacticities using the SANS technique and the discussions about the tacticity effect on polymer mixtures in comparison with their interaction parameters. Furthermore, the properties of blends of syndio-tactic polystyrene (SPS) and atactic polystyrene (APS) are presented focusing on the improvement of chemical resistance. 

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Ho and co-workers [62] used SAXS, among other techniques, to examine microphase separation and crystallisation in a melt-mixed blend of syndiotactic polystyrene (sPS) with a block copolymer of styrene and ethylene propylene. 

Recyclable blends of syndiotactic polystyrene, sPS, were prepared by blending sPS with a copolymer of styrene with either maleic anhydride (MA), or with glycidyl methaciylate (GMA), and with an elastomer, e.g., SEES, SBS, SBR, EPDM. The compositions showed good impact resistance, elongation and retention of physical properties upon... 

BLENDS OF SYNDIOTACTIC POLYSTYRENE WITH POLYAMIDE TABLE 16.4 USCAR Class III and IV Thennal Stability Test Results... 

The possible entrapment of solvent in polymer crystals has been demonstrated by Malik et al., who investigated blends of syndiotactic polystyrene (s-PS) with organic solvents such as naphthalene, benzene, toluene, and so on [63]. Subsequently, the phase diagrams of these polymer-solvent systems, thus established, exhibited the liquidus and solidus lines, showing crystalline phases of s-PS and/or its modifications such as crystallo-solvates, in which the solvent molecules were trapped in the s-PS crystals [63-65]. The experimental evidence has led to the suggestion of possible entrapment of solvent in polymer crystals, forming solvated crystals [63]. 

Blends of syndiotactic styrene-/ -methylstyrene copolymers (SPMS) with poly(styrene)-block-poly(ethylene-co-butylene)-block-polystyrene (SEBS) has been reported. [21] No significant effects on the tensile modulus and strength were observed for blends containing less than 10% SEBS. SEM of drawn samples of the blends showed that the dispersed SEBS phase had been extended to about the same extent as the bulk blend, indicating good adhesion between the two phases. 

Nanocomposites of syndiotactic polystyrene (sPS) employing MMT-hexadecyltributylphosphonium [40, 41] and high-impact polystyrene (H1PS)/MMT-hexadecyltriphenylphosphonium [42] were prepared by melt-blending and in situ coordination-insertion polymerization. Partially exfoliated or intercalated materials were obtained in all cases, and a decrease of crystallinity of sPS was observed. However, the presence of clay did not have a strong influence on the sPS thermal transitions. Thermal decomposition of the material was slowed and mechanieal properties were improved in the presence of low organoclay content. Intercalated HIPS nanocomposites were obtained, with improved thermal and flame retardant properties compared to pure HIPS (Figure 3.8). 

Dikshit, A. K., Kaito, A. Effects of the oriented mesophase on the cold crystallization of syndiotactic polystyrene and its blend with poly(2,6-dimethyl-l,4-phenylene oxide). /. Polym. Sci Part B Polym. Phys., 41(14), 1665-1675 (2003). 

Blends of two immiscible polymers are created to yield a material with properties that could not be obtained otherwise. Each component of the blend overcomes the property deficiencies of the other component of the blend. In the case of syndiotactic polystyrene (SPS)/polyamide (PA nylon) blends, the blends have improved strength, ductility, and creep versus SPS formulations, and the blends have improved dimensional stability and flow versus nylon compounds. Other attributes of the SPS/nylon blends are low specific gravity (lower weight parts), high thermal diffusivity (low cycle time), excellent electrical properties, good chemical resistance, and excellent United States Council for Automotive Research (USCAR) electric wiring components test performance. In this chapter, the composition, properties, and applications for SPS/ nylon blends will be reviewed. 

Other symbols occasionally used in the literature include (br) for branched materials and (iso), (syndio), and (a) for isotactic, syndiotactic, and atactic structures respectively. No symbol appears to exist for mechanical blends, although these materials are obviously important. Where necessary the symbol -m- will denote a mechanical blend, for example, poly(styrene-m-butadiene) for a mechanical blend of polystyrene with polybutadiene. 

Syndiotactic polystyrene (sPS) is a hard, stiff material with high temperature stability and excellent isolator properties. The E-module of ca. lO Mpa is similar to that of polyamide 66, and therefore much higher than in amorphous polystyrene. These properties lead to new, very interesting apphcations, especially Lf sPS is blended with polyamides [6]. 

Blends of PPO with PS containing sulfonated and carboxylated groups have been reported in various studies [394-396]. The miscibility of sulfonated PS with PPO, sulfonated PPO with PS and blends of the sulfonated polymers was reported by Hseih and Peilfer [394]. Miscibility was maintained with sulfonation levels up to 2-4mol% for PS with sulfonated PPO and sulfonated PS with PPO. When both polymers were sulfonated, phase separation occurred at higher levels (> 10mol% sulfonation). The miscibility can be influenced by counter ion, as noted in a comparison of a Zn + neutralized sulfonic acid modified PS, which exhibited a larger miscibility window with PPO than the Na neutralized coimterpart [396]. Syndiotactic polystyrene was noted to be miscible over the entire composition range in amorphous blends with PPO, where the Tg versus composition followed the Fox equation predictions [397]. Isotactic polystyrene miscibility with PPO has also been observed, with crystallization and orientation data reported on the blend [398]. 

Poly(cyclohexyl acrylate) was shown to be miscible with PS with ucst behavior [720]. Random copolymers of cyclohexyl acrylate with n-butyl acrylate showed miscibility with PS above 50% cyclohexyl acrylate[721]. Poly(cyclohexyl methacrylate)/isotactic PS blends showed miscibility based on calorimetry and NMR studies [722]. The NMR results showed homogeneous behavior at a scale of 2.5-3.5 nm. Poly(4-trimethylsilyl styrene) miscibility with polyisoprene was observed with a lest behavior (critical temperature = 172 ° C at degree of polymerization of 370) [723]. The interaction parameter, showed the following relationship = 0.027—9.5/T. Isotactic and syndiotactic polystyrene both exhibit crystallinity, whereas atactic polystyrene is amorphous. Atactic PS/isotactic PS blends exhibited crystallization kinetics, which decreased linearly with atactic PS addition indicating miscibility [724]. The TgS of aPS and iPS are identical, thus Tg methods could not be employed to assess miscibility. Atactic PS/syndiotactic PS blends were also noted to be miscible with rejection of atactic PS in the interfibrillar region between the lamellar stacks of sPS [725]. 

Lim, J. et al. A novel preparation method of maleic anhydride grafted syndiotactic polystyrene and its blend performance with nylon 6. Polymer Bulletin (Berlin, Germany), 48(April 5), 397 05 (2002). 

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