Immiscible Blends Of Polystyrene Research Articles

Dispersion and Localization Behavior of Modified MWCNTs in Immiscible Polymer Blends of Polystyrene and Polybutadiene and in Corresponding Nanostructured Block Copolymers

The influence of carbon nanotube (CNT) modification on the dispersion and localization behavior of the CNTs in immiscible blends of polystyrene (PS) and polybutadiene (PB), and in the nanostructured morphology of a star-shaped styrene-butadiene based block copolymer (BCP), was studied to form a basis for the development of functional materials with defined electrical property profiles. Unmodified multi-walled CNTs (MWCNTs) were dispersed in PS, PB and PS/PB blends by solution mixing. Additionally, MWCNTs were functionalized with n-octadecylamine and monoamino-terminated polystyrene to increase the compatibility between the homopolymers and the nanofiller. The MWCNT dispersion and the blend morphology formation were studied using transmission light microscopy and scanning electron microscopy. The MWCNT dispersion could be significantly improved by the modification of the MWCNTs. All MWCNT types were found to preferably localize in the PS phase of the PS/PB blend. However, only blends containing unmodified MWCNTs were electrically conductive. Similar effects were found in BCP/MWCNT composites. The BCP was already electrically conductive with a filler content of 0.1 wt % of unmodified MWCNTs. The stress–strain behavior of the BCP was slightly influenced by MWCNT addition and CNT modification. The dispersability of MWCNTs was significantly improved by CNT functionalization, which indicates a strong polymer-filler interaction.

Mathematical modeling of the catalytic degradation of polystyrene in the presence of aluminum chloride

We model the effect of the catalyst AlCl 3 on polystyrene (PS). Detailed experimental studies were previously carried out on the effect of AlCl 3 on PS, as part of an effort to understand how to minimize the degradation of PS during the Friedel–Crafts alkylation performed to obtain a graft copolymer from immiscible blends of PS and a polyolefin (PO). In the present work three mathematical models for the catalytic degradation of PS are proposed, all of which consider that reaction starts with the elimination of a phenyl group from the PS chain, followed by either chain scission or a change in the chain structure. The models vary in the way they consider the strength of the main chain bonds, or the reactivity of modified PS chains. Kinetic parameters for each model are estimated. Although the three proposed models could be used to represent our own experimental data, one is more accurate. Experimental data from other authors are used to evaluate its capabilities. Based on the predictions of the better model, we discuss conditions to minimize PS scission, such as operating at low temperatures and AlCl 3 concentrations, and using short processing times.

Fourier transform infrared and second derivative ultraviolet spectrometry in determining polystyrene‐poly(4‐methylstyrene) blend composition

AbstractPolymer blend usage has increased in recent years as the blends provide a convenient means for modifying polymer properties. It is often necessary to determine the percents or ratios of the polymers present in a blend. One blend of interest is the immiscible blend of polystyrene (PS) and poly(4‐methylstyrene) (P4MS). The percentages were determined by two methods: Fourier transform infrared (FTIR) spectroscopy and second derivative ultraviolet (UV) spectroscopy. The peak ratio versus percent polymer technique was used in both methods. For the FTIR, the ratio of the absorbance values for the out‐of‐plane CH para‐substituted bending vibration of P4MS at 813 cm−1 and the out‐of‐plane monosubstituted CH bending vibration for PS at 757 cm−1 were ratioed. For derivative UV, the vibrational structures of the aromatic secondary bands were used: the 269 nm minimum for PS and 275 nm minimum for P4MS. The derivative UV method gave considerably better results and also had the advantage of requiring less sample due to its greater sensitivity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3400–3403, 2006

Compatibilization of PS and PA6 Blends by Means of Poly(oxyalkylene)amine Modified Styrene-Maleic Anhydride Copolymer

The compatibilization effect of SMA-co-M2070-co-DAP comb-like copolymers, SMMD, on immiscible blends of polystyrene (PS) and polyamide-6 (PA6) is examined in terms of phase structure, thermal behavior, dynamic mechanical analysis, and mechanical properties. A series of SMMD copolymers are synthesized and confirmed by the FT-IR analysis. These compatibilizers have different amphiphilic properties depending on the content of hydrophilic poly(oxyethylene) segments (M2070) and the molar ratio of MA/amine. The morphologies of PS/PA6, affected by the increasing amount of SMMD compatibilizer, show a more regular and finer dispersion. The sizes of dispersed particles have no marked changes over the saturation level of compatibilizer. The glass transition temperatures of the blends are between that of PS and PA6, while the added SMMD copolymer is mainly located at the interface. Using these SMMD copolymers, the compatibilized blends show some improvements in mechanical properties, including Izod impact strength and flexural properties. The graft poly(oxyethylene) and amide functionalities in SMMD structures in forming hydrogen bonding with PA6 and, the polystyrene backbone in π–π interaction with PS facilitate the compatibilizing effect.

Use of Fourier transform infrared and second derivative ultraviolet spectrometry in determining polystyrene–poly(4‐vinylpyridine) blend composition

AbstractPolymer blend usage has increased in recent years as the blends provide a convenient means for modifying polymer properties. It is often necessary to be able to determine the percentages or ratios of polymers present in a blend. One blend of interest is the immiscible blend of polystyrene (PS) and poly(4‐vinylpyridine) (P4VP). The percentages were determined by two methods: Fourier transform infrared (FTIR) spectroscopy and second derivative ultraviolet (UV) spectroscopy. The peak ratio versus percentage polymer technique was used in both methods. For FTIR, the ratio of the absorbance values of the out‐of‐plane CH bending vibration of P4VP at 822 cm−1 and the aromatic C  C stretch for PS at 1493 cm−1 were ratioed. For derivative UV, the vibrational structure of the aromatic secondary bands was used: 269 nm minimum for PS and the 271 nm maximum for P4VP. Both methods gave excellent and comparable results. The derivative UV determination had the advantage of requiring less sample due to its greater sensitivity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2422–2426, 2005

Compatibilizing Effect of Poly(Styrene-block-2-Vinylpyridine) Copolymer on Polystyrene/Ethylene-Based Ionomer Resin Blends

The effect of adding the diblock copolymer poly(styrene-block-2-vinylpyridine) P(S-b-2VP] to immiscible blends of polystyrene (PS)/ethylene based ionomer resin [zinc salt of poly(ethylene–co–methacrylic acid)] on the morphology, dynamic mechanical, and mechanical properties of the blends has been investigated. The diblock copolymer was synthesized by sequential anionic copolymerization and was melt-blended with PS and ionomer. Scanning electron microscopy (SEM) showed that the added block copolymer reduced the domain size of the dispersed phase in the blends. Dynamic mechanical analysis (DMA) revealed that the extent of compatibility between PS and ionomer affected the values tan δ and glass transition temperature Tg of the blends. Notched impact strength, tensile strength, and elongation at break were determined as a function of different amounts of added P(S-b-2VP) in the blends. The compatibilizing effect of the diblock copolymer is most probably the result of its location at the interface between the PS and the ionomer phases and penetration of the blocks into the corresponding phases, that is, the polystyrene block enters the PS matrix, and the poly(2-vinylpyridine) block interacts with ionomer through ion-ligand interaction.

Mechanical properties of polystyrene/polyamide 6 blends compatibilized with the ionomer poly(styrene‐co‐sodium acrylate)

AbstractThe compatibilizing effect of the ionomer, poly(styrene‐co‐sodium acrylate) (PSSAc), on immiscible blends of polystyrene (PS)/polyamide 6 (PA6) was studied by mechanical tests and scanning electron microscopy. The PSSAc acts as an effective compatibilizer because both the deformation at break (%) obtained by tensile stress–strain tests and the impact rupture energy are larger in blends containing small amounts of PSSAc. The morphologies of the fractured surfaces produced by tensile stress–strain tests of blends with or without the ionomer confirm that PSSAc increases the interfacial adhesion between PS and PA6 phases. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2545–2551, 2004

Phase morphology development and melt rheological behavior in nylon 6/polystyrene blends

AbstractPhase morphology development in immiscible blends of polystyrene (PS)/nylon 6 was investigated. The blends were prepared by melt blending in a twin‐screw extruder. The influence of the blend ratio, rotation speed of the rotors, and time of mixing on the phase morphology of the blends was carefully analyzed. The morphology of the samples was examined under a scanning electron microscope (SEM) and the SEM micrographs were quantitatively analyzed for domain‐size measurements. From the morphology studies, it is evident that the minor component, whether PS or nylon, forms the dispersed phase, whereas the major component forms the continuous phase. The 50/50 PS/nylon blend exhibits cocontinuous morphology. The continuity of the dispersed phase was estimated quantitatively based on the preferential solvent‐extraction technique, which suggested that both phases are almost continuous at a 50/50 blend composition. The effect of the rotor speed on the blend morphology was investigated. It was observed that the most significant breakdown occurred at an increasing rotor speed from 9 to 20 rpm and, thereafter, the domain size remained almost the same even when the rotor speed was increased. The studies on the influence of the mixing time on the blend morphology indicated that the major breakdown of the dispersed phase occurred at the early stages of mixing. The melt rheological behavior of the blend system was studied using a capillary rheometer. The effect of the blend ratio and the shear stress on the melt viscosity of the system was investigated. Melt viscosity decreased with increase in the shear stress, indicating pseudoplastic behavior. With increase of the weight fraction of PS, the melt viscosity of the system decreased. The negative deviation of the measured viscosity from the additivity rule indicated the immiscibility of the blends. The domain size versus the viscosity ratio showed a minimum value when the viscosities of the two phases were matched, in agreement with Wu's prediction. The morphology of the extrudates was analyzed by SEM. From these observations, it was noted that as the shear rate increased the particle size decreased considerably. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3537–3555, 2002

Compatibilizing effects of poly(styrene- co-methacrylic acid) on immiscible blends of polystyrene and poly(ethylene glycol)

In this study, compatibilizing effects of poly(styrene- co-methacrylic acid) (P(S- co-MAA)) with various MAA contents on immiscible blends of polystyrene (PS) and poly(ethylene glycol) (PEG) blends are investigated by scanning electron microscopy (SEM) and infrared spectroscopy (FT-IR). It is found by SEM observation that the sizes of dispersed droplets in PS/PEG blends are decreasing with increasing P(S- co-MAA) contents. Therefore, P(S- co-MAA)s act as compatibilizing agents for PS/PEG blends. On the basis of FT-IR analysis, the compatibilizing effects of P(S- co-MAA) on PS/PEG blends is explained by the associative interaction between MAA unit of P(S- co-MAA) and ether oxygen of PEG and miscibility of PS and relatively long styrene sequence of P(S- co-MAA).

Compatibilization of blends of polystyrene and zinc salt of sulfonated polystyrene by poly(styrene- b-4-vinylpyridine) diblock copolymer

The compatibilizing effect and mechanism of poly(styrene- b-4-vinylpyridine) diblock copolymer, P(S- b-4VPy), on the immiscible blend of polystyrene (PS)/zinc salt of sulphonated polystyrene (Zn-SPS) were studied. SEM results show that the domains of the dispersed phase in the blend become finer. DSC experiments reveal that the difference between the two T g's corresponding to the phases in the blends becomes larger on addition of P(S- b-4VPy), mainly resulting from dissolving of the poly(4-vinylpyridine (P4VPy) block in the Zn-SPS phase. FTIR analysis shows that compatibility of P4VPy and Zn-SPS arises from the stoichiometric coordination of the zinc ions of Zn-SPS and pyridine nitrogens of P4VPy. SAXS analysis indicates the effect of the P(S- b-4VPy) content on the structure of the compatibilized blends. When the content of the block copolymer is lower than 4.1 wt%, the number of ion pairs in an aggregate in the Zn-SPS becomes smaller, and aggregates in ionomer in the blend become less organized with increasing P(S- b-4VPy). When the P(S- b-4VPy) content in the blend is up to 7.4 wt%, a fraction of P(S- b-4VPy) form a separate domain in the blend.

Distribution of MBS emulsion particles in immiscible polystyrene/SAN blends

AbstractThe effect of mixing technique and sequence on the distribution of methacrylated‐butadienestyrene (MBS) emulsion particles in immiscible blends of polystyrene (PS) and a styrene/acrylonitrile copolymer (SAN) was examined using transmission electron microscopy. The shell of the emulsion particle is essentially poly(methyl methacrylate) (PMMA), which is miscible with SAN but immiscible with PS. In simple thermodynamic terms, the MBS particle should have an affinity for SAN over PS. It was found, however, that the sequence of mixing had a strong influence on the location of the MBS particles. If the PS‐SAN interface is established before the addition of the MBS particles, the MBS particles are located exclusively in the SAN phase. If the MBS particles are present at the time the PS‐SAN interface is formed, then the particles line up at the interface.

Polymer blends and alloys—a review of selected considerations

AbstractA brief overview of the important issues governing the behavior of polymer blends is presented. Thermodynamic issues which determine the phase behavior of blends are reviewed and qualitatively related to physical interactions between blend components. The influence of melt processing conditions on the resulting properties and behavior of both miscible and immiscible blends is reviewed. The physical properties of blends are reviewed and illustrated by examples from recent work on miscible blends of polycarbonate with a copolyester and on the immiscible blends of polystyrene with high density polyethylene.