Butylene-styrene Triblock Copolymer Research Articles

A novel approach for fabricating adjustable zero field-modulus magnetorheological elastomer based on IPN matrix

Toughening modification of magnetorheological elastomer (MRE) is crucial necessity for developing intelligent MRE based devices. To prepare high performance MRE, the thermoplastic elastomer styrene-ethylene butylene-styrene triblock copolymer (SEBS) was added into polybutadiene rubber (BR) to prepare BR/SEBS interpenetrating network (IPN) matrix based MRE. The anisotropic samples were prepared by different vulcanization method under a magnetic field. The mechanical properties of MRE was measured by rheometer. The experimental results showed that the zero-field modulus of MRE was increased with the addition of SEBS. The measurement result of dynamic thermomechanical analysis (DMA) showed that the two-phase heterogeneous system was formed in matrix. The zero-field modulus of this MRE can be adjusted by the content of SEBS and vulcanization time and temperature since the SEBS does not participate in the vulcanization reactions and possess fluidity at high temperature. The MRE with adjustable zero-field modulus have promising advantages in the application of adaptive tuned vibration absorbers.

Influence of halloysite nanotubes (HNTs) on morphology, crystallization, mechanical and thermal behaviour of PP/ABS blends and its composites in presence and absence of dual compatibilizer

Halloysite nanotubes (HNTs) filled 80/20 (wt/wt) polypropylene (PP)/acrylonitrile butadiene styrene (ABS) blends and its composites in presence and absence of dual compatibilizer (polypropylene grafted maleic anhydride (PP-g-MA), and styrene-ethylene, butylene-styrene triblock copolymer grafted with maleic anhydrite (SEBS-g-MA)) have been prepared using twin screw extruder followed by injection moulding. Significant refinements in dispersed ABS droplets diameter and interparticle distance between dispersed ABS droplets were observed in case of HNTs filled 80/20 (wt/wt) PP/ABS blends and its composites in presence of PP-g-MA and SEBS-g-MA. This has resulted in significant enhancement in tensile and impact properties of HNTs filled 80/20 (wt/wt) PP/ABS blends and its composites in presence of PP-g-MA and SEBS-g-MA. Refinement in morphology of dispersed ABS phase results in decrease in crystallinity of HNTs filled 80/20 (wt/wt) PP/ABS blends and its composites in presence of PP-g-MA and SEBS-g-MA. In addition, HNTs act as heterogeneous nucleating agent for the growth of PP crystals, and hence crystallization rate of HNTs filled 80/20 (wt/wt) PP/ABS blends and its composites in presence and absence of PP-g-MA and SEBS-g-MA increases. Thermal stability also increases in case of HNTs filled 80/20 (wt/wt) PP/ABS blends and its composites in presence and absence of PP-g-MA and SEBS-g-MA.

A pH sensor based on force generated by pH-dependent polymer swelling

We have demonstrated the feasibility of a new type of pH sensor by combining a bead of porous lightly crosslinked diethanolamine derivatized poly(vinylbenzyl chloride) with a strain gauge, i.e. a pressure sensitive resistor. The polymer bead is toughened with Kraton G1652, a styrene-ethylene,butylene-styrene triblock copolymer. The sensor is constructed so that the shrunken form of the bead is held in contact with the strain gauge with a small force. Increases in the hydrogen ion concentration protonate the diethanolamine introducing a positive charge onto the polymer backbone. This results in an electrostatic swelling force that causes the polymer to swell. This is detected as a change in strain gauge resistance that is readout via a Wheatstone bridge. When the pH of 0.10 M buffers is changed from 10 to 4, the response time is 390 s for a bead that is 0.25 mm in diameter in the shrunken state. The response varies with the square of the bead radius. The magnitude of the response is highly correlated with the penetration modulus, a measure of the extent to which the bead resists deformation when subjected to an external force. The response to pH appears to be shifted by the application of pressure in the sensor. This instrumentally simple approach to sensing has the potential to be stable and long-lived if the polymer bead can undergo a large number of swelling/shrinking cycles without changing mechanical properties.

The toughening behavior in propylene-ethylene block copolymer filled with carbon black and styrene-ethylene butylene-styrene triblock copolymer

This work examines the toughening behavior of propylene-ethylene block copolymer (Co-PP) filled with carbon black (CB) and styreneethylene butylene-styrene triblock copolymer (SEBS). Appropriate amounts of the two components are mixed through melt-blending in a twin-screw extruder. The blended pellets, following preparation in a series of specimens by injection molding, are studied and compared. A scanning electron microscope (SEM) morphology study of the impact-fractured surfaces verifies the changes in fracture mechanisms at various temperatures and SEBS contents. In addition, the flexural modulus, tensile strength, heat distortion temperature (HDT), and dynamic mechanical properties are also studied here. According to those results, the blending of CB in Co-PP not only improves the impact strength, but also enhances the flexural modulus and tensile strength. However, the HDT of the Co-PP/CB blends decreases with a greater filler content. Moreover, SEBS markedly upgrades the impact endurance in the lower temperature range when blended with Co-PP, due to the increased compatibility in the interface between SEBS particles and the Co-PP matrix.

Morphology and porosity of poly(vinylbenzyl chloride) beads containing styrene–ethylene, butylene–styrene triblock copolymer1Based on a paper presented at the Fifth International Meeting on Chemical Sensors, Rome, Italy, 11–14 July 1994.1

Abstract Because crosslinked, porous poly(vinylbenzyl chloride) is an attractive substrate for sensors and actuators based on polymer swelling, its properties were studied as a function of formulation. Polymer beads were formed by suspension copolymerization of vinylbenzyl chloride and divinylbenzene in the presence of xylene/dodecane and Kraton G1652, a styrene–ethylene, butylene–styrene triblock copolymer. As polymerization proceeds, the dodecane phase separates forming aliphatic domains within the aromatic polymer. After polymerization, the xylene/dodecane is removed to yield a porous material. These materials were examined by scanning electron microscopy and mercury porosimetry. It was found that including Kraton G1652 in the formulation leads to morphologies with greatly increased surface area compared with morphologies observed without Kraton G1652. Formulations with 2% Kraton contained a large number of small pores in a continuous aromatic polymer matrix. Formulations with 8 and 14% Kraton have a morphology consisting of small connected spheres surrounded by empty void space.

The influence of composition on the properties of pH-swellable polymers for chemical sensors

Abstract Aminated polystyrene swells at low pH due to electrostatic repulsion between charged sites on the polymer. The effects of polymer formulation on the rate and degree of swelling and on the penetration modulus have been evaluated for porous aminated polystyrene beads prepared by suspension polymerization. The following parameters were varied in a 3×3×3×2 factorial experiment: 1) percent crosslinking, 2) percent porogenic solvent, 3) composition of porogenic solvent and 4) level of Kraton G1652, a styrene–ethylene, butylene–styrene triblock copolymer, added to toughen the polymer. The degree of swelling decreases at higher levels of crosslinking. Swelling is greater when the polymer morphology is continuous rather than consisting of connected small spheres. The percentage of xylene in the porogenic solvent affects the degree of swelling for underivatized beads in toluene but not for derivatized beads in acid. The rate of swelling of underivatized beads in toluene appears to involve toluene entering the pore space of the bead by capillary action. However, rates of swelling of derivatized bead in acid appear to be governed by the rate at which protons move through the bulk of the polymer rather than involving transport through pore space. The penetration moduli are small for all beads and depend on the degree of crosslinking, the amount of pore space in the bead and the polymer morphology.

Aminated polystyrene membranes for a fiber optic pH sensor based on reflectance changes accompanying polymer swelling

We have prepared toughened, porous, aminated polystyrene membranes that undergo an increase in reflectance as the pH increases from 6.8 to 8.0. Vinylbenzyl chloride (VBC) is copolymerized with divinylbenzene (DVB) in the presence of a toughening agent, Kraton G1652, a styrene-ethylene, butylene-styrene triblock copolymer, and a porogenic solvent, xylene/ dodecane. The optimum formulation for sensing is 2% DVB (mol DVB/mol VBC), 2% Kraton (g Kraton/g VBC) and 40% (v/v) 2∶1 xylene: dodecane. Benzoyl peroxide is used as the initiator. The components are partially polymerized at 85 °C to a viscosity of 600–800 centipoise. The polymerization is then stopped by reducing the temperature. A drop of the partially polymerized solution is confined between two microscope slides and the polymerization reaction is completed. The resulting membrane is then swollen in 1,4-dioxan and reacted with diethanolamine. These membranes have been incorporated into a pH sensor based on changes in reflected intensity measured through a bifurcated bundle of twenty unbuffered 50/55 core/cladding glass-on-glass optical fibers with numerical apertures of 0.57. The resulting sensor is stable and requires inexpensive optical components, a red-emitting LED as the source and a silicon photodiode as the detector.

Toughening isotactic polypropylene and propylene-ethylene block copolymer with styrene-ethylene butylene-styrene triblock copolymer

Dynamic mechanical properties, low-temperature impact behavior, flexural modulus and heat distortion temperature (HDT) of isotactic polypropylene (i-PP) and propylene-ethylene block copolymer (Co-PP) toughened with styrene-ethylene butylene-styrene triblock copolymer (SEBS), at blending ratios of 0–30 phr, were studied and compared. A scanning electron microscopic morphology study of the impact-fractured surfaces demonstrated the changes in fracture mechanisms at various temperatures and SEBS contents. SEBS remarkably improves the impact endurance in the lower-temperature range when blended with Co-PP in comparison with i-PP, due to the increased compatibility in the interface between SEBS particles and the Co-PP matrix.

Mechanically robust amine derivatized polystyrene for pH sensing based on polymer swelling

Beads that change size as a function of pH have been prepared by suspension polymerization of vinylbenzyl chloride crosslinked with divinyl benzene followed by reaction with pure diethanolamine. Toluene is added to induced porosity, and Kraton G1652, a styrene-ethylene,butylene-styrene triblock copolymer, is included to increase mechanical robustness. The optimum formulation includes 48% toluene by volume and 2% (w/w) Kraton G1652. As the pH decreases, protonation of the amine puts a charge on the amine, causing the polymer to swell due to electrostatic repulsion between charged sites on the polymer. After the polymer is conditioned by exposure to acid, the ratio of the diameter in acid to the diameter in base is as high as 1.6 at an ionic strength of 0.10 M. The diameter ratio decreases with increasing ionic strength as predicted by theory. The diameter changes continuously from pH 6.0 to 8.0. This means that immobilization shifts the p K a of the amine. The polymer beads undergo many swelling and shrinking cycles without degrading mechanically but are softer than desired for use in a pH sensor based on polymer swelling.