Effect of copper nanoparticles on the properties of SEBS/PP compounds

This study evaluated the adoption of copper nanoparticles (CuNPs) as an antimicrobial agent in thermoplastic elastomer compounds (TPEs) based on styrene-(ethylene-butylene)-styrene triblock copolymer (SEBS) and polypropylene (PP) for use in the fabrication of automotive air-conditioning systems. The nanocompounds were prepared using a co-rotating double screw extruder and CuNPs were pre-dispersed in polypropylene at weight proportions of 0%, 0.6% and 1.0%. The physical (density), mechanical (tensile and hardness), thermal (differential scanning calorimetry and thermogravimetry) and antimicrobial properties were evaluated on injection molded plates. The antimicrobial properties were evaluated for the bacteria Staphylococcus aureus and Escherichia coli and fungal species commonly found in automotive air conditioners. The results from antibacterial tests showed a reduction of 99.9% in counts of both bacteria tested. There was no fungal growth on the loaded TPE surface. At the tested levels, the addition of CuNPs did not cause significant variations in the TPE properties evaluated.     

Poly(lactic acid)/(styrene‐ethylene‐butylene‐styrene)‐g‐maleic anhydride copolymer/sepiolite nanocomposites: Investigation of thermo‐mechanical and morphological properties

In this study, sepiolite nanoclay is used as reinforcing agent for poly(lactic acid) (PLA)/(styrene‐ethylene‐butylene‐styrene)‐g‐maleic anhydride copolymer (SEBS‐g‐MA) 90/10 (w/w) blend. Effects of sepiolite on thermal behavior, morphology, and thermomechanical properties of PLA/SEBS‐g‐MA blend were investigated. Differential scanning calorimetry results showed 7% improvement in crystallinity at 0.5 wt% of sepiolite. The nanocomposite exhibited approximately 36% increase in the tensile modulus and 17% increase in toughness as compared with the blend matrix at 0.5 and 2.5 wt% of sepiolite respectively. Field emission scanning electron microscopy and transmission electron microscopy images exhibited sepiolite‐induced morphological changes and dispersion of sepiolite in both PLA and SEBS‐g‐MA phases. Dynamic mechanical analysis and wide angle X‐ray diffraction present evidences in support of the reinforcing nature of sepiolite and phase interaction between the filler and the matrix. This study confirms that sepiolite can improve tensile modulus and toughness of PLA/SEBS‐g‐MA blend.     

A comparative study of effects of SEBS and EPDM on the water tree resistance of cross-linked polyethylene

In this work, we investigated the effects of an ethylene propylene diene monomer (EPDM) and poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) on the water tree resistance in cross-linked polyethylene (XLPE). The XLPE/EPDM and XLPE/SEBS blend samples were prepared by melting compounding and subsequent compression molding. It was found that SEBS could greatly increase the water tree resistance of XLPE and the resistance performance was improved with SEBS content within 15 phr, whereas EPDM did not show any improvement in the water tree resistance of XLPE. The frequency dependent behaviors of the water treeing phenomena and the effects of EVA on the water tree resistance of XLPE/EPDM and XLPE/SEBS blends were also investigated. The water treeing phenomena of the blends were interpreted from the viewpoints of electro-mechanical and electro-chemical mechanisms.     

Microstructure of triblock copolymers in asphalt oligomers

A model asphalt has been separated into two parts, asphaltene and maltene, through solvent extraction by n-heptane. The interactions of asphaltene and maltene with the triblock copolymer poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) were investigated by transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), dynamic mechanical analysis (DMA), and differential scanning calorimetry (DSC). Asphaltene was found to be essentially immiscible with both blocks of SEBS, while maltene was miscible with SEBS. An unusual sequence of morphological transformations of SEBS microstructure with respect to the addition of maltene was observed. The morphology transformed from hexagonal cylinder, to perforated layers, to lamellae and then back to the original hexagonal cylinder. The observed transformation reflects a limited solubility for both S and EB domains: at lower concentration maltene is a preferential additive for S domains, while increasing concentration the swelling of EB-rich microdomains by maltene becomes significant. The basic understanding of the interactions of the components of asphalt with SEBS gives a simple path to characterize and predict the microstructure of triblock copolymers in asphalt oligomers. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2857–2877, 1997     

Palladium‐catalyzed phosphonation of SEBS block copolymer

Phosphonic acid‐bearing styrene–ethylene/butylene–styrene (SEBS) block copolymer was synthesized by bromination and subsequent palladium‐catalyzed phosphonation of SEBS. The phosphonated block copolymer was characterized by spectroscopic, thermal, and conductivity measurements. The new polymer shows good ion‐exchange capacity of ～0.7 meq/g and proton conductivity of around 2–4 mS/cm (at room temperature and 100% relative humidity) which is in good agreement with literature value of other phosphonated materials. This value was obtained despite a relatively low degree of phosphonation, demonstrating the ability of the phase separated nature of block copolymers to promote proton conductivity. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5431–5441, 2008     

Towards Finding The Best Existing Model for Prediction of Morphology of Ternary Polymer Blends

The goal of this study was to investigate the capability of conceptual models for correct prediction of ternary blends morphology. All existing models, including spreading coefficient, relative interfacial energy, dynamic interfacial energy (DIE), and modified DIE were employed to predict the type of morphology of the polyamide 6/poly(styrene-co-acrylonitrile)/poly(styrene-b-(ethylene-co-butylene)-b-styrene) ternary system. Various samples with different compositions were prepared and predictions of the models were compared with the experimental phase morphology of the samples based on scanning electron microscopy micrographs. Additionally, the effect of elasticity of the matrix component on the both predictions and experimental phase structures of the blends was studied. It was demonstrated that, among the available phenomenological models, the modified DIE can comprehensively represent the most correct predictions for the morphology of ternary polymer blends.     

Preparation of Size Controllable Polypyrrole Sub‐Microcapsules Using SEBS Copolymer as the Building Block

Summary: SEBS is used as building blocks to fabricate size controllable polypyrrole (PPy) capsules. Polypyrrole shells grow on the surfaces of the size controllable oxidant sub‐microparticles dispersed in the solution cast film of a SEBS copolymer by vapor phase polymerization. After washing in ethanol, PPy sub‐microcapsules dispersed in a SEBS matrix are obtained. This technique shows advantages of lower cost and less pollution, as compared with the gold‐template method reported in the literature.

A TEM image of polypyrrole sub‐microcapsules dispersed in a SEBS matrix.     

Macromolecular dynamics of sulfonated poly(styrene-b-ethylene-ran-butylene-b-styrene) block copolymers by broadband dielectric spectroscopy

Macromolecular dynamics of sulfonated poly(styrene-b-ethylene-ran-butylene-b-styrene) (sSEBS) triblock copolymers were investigated using broadband dielectric spectroscopy (BDS). Two main relaxations corresponding to the glass transitions in the EB and S block phases were identified and their temperature dependences were VFT-like. T_g for the S block phase shifted to higher temperature due to restrictions on chain mobility caused by hydrogen bonded SO₃H groups. While the EB block phase T_g appeared to remain constant with degree of sulfonation in DMA experiments, it shifted somewhat upward in BDS spectra. A low temperature relaxation beneath the glass transition of the EB block phase was attributed to short range chain motions. The Kramers–Krönig integral transformation was used to calculate conductivity-free loss permittivity spectra from real permittivity spectra to enhance true relaxation peaks. A loss permittivity peak tentatively assigned to relaxation of internal S-EB interfacial polarization was seen at temperatures above the S block phase glass transition, and the temperature dependence of this relaxation was VFT-like. The fragilities of the EB and S block domains in sulfonated SEBS decreased after sulfonation. The temperature dependence of the dc conduction contribution to sSEBS loss spectra also followed VFT-like behavior and S block segmental relaxation time correlated well with conductivity according to the fractional Debye–Stokes–Einstein equation.     

Non-fluorinated proton-exchange membranes based on melt extruded SEBS/HDPE blends

This paper reports on functional polymer blends prepared by melt-processing technologies for proton-exchange membrane applications. Styrene–ethylene/butylene–styrene (SEBS) and high-density polyethylene (HDPE) were melt blended using twin-screw compounding, extruded into thin films by extrusion–calendering. The films were then grafted with sulfonic acid moieties to obtain ionic conductivity leading to proton-exchange membranes. The effect of blend composition and sulfonation time was investigated. The samples were characterized in terms of morphology, microstructure, thermo-mechanical properties and in terms of their conductivity, ion exchange capacity (IEC) and water uptake in an effort to relate the blend microstructure to the membrane properties. The HDPE was found to be present in the form of elongated structures which created an anisotropic structure especially at lower concentrations. The HDPE increased the membrane mechanical properties and restricted swelling, water uptake and methanol crossover. Room temperature through-plane conductivities of the investigated membranes were up to 4.5E−02 S cm⁻¹ at 100% relative humidity, with an ionic exchange capacity of 1.63 meq g⁻¹.