Melt/solution processable conducting polyaniline: Elastomeric blends with EVA

Polyaniline (PANI) protonated with dopant, the sulfonic acid of 3‐pentadecylphenoxyacetic acid (SPDPAA; synthesized from an inexpensive naturally existing biomonomer, cardanol), was blended with an elastomeric polymer, the ethylene vinyl acetate (EVA) copolymer. Blending was performed either by emulsion polymerization of aniline into the EVA matrix or by the solution‐mixing method. Thin films were prepared by the conventional melt‐processing technique for an emulsion‐polymerized system and by the solution‐casting method for a solution‐mixed system. In the case of the emulsion‐polymerized system, the percolation threshold occurs at a very low weight percentage of PANI, and a maximum conductivity value of 0.85 S cm^?1 was obtained for 28.5 wt % of PANI. These elastomeric conducting blends were characterized by elemental analysis, FTIR and UV‐visible spectral analysis, conductivity measurements, SEM, XRD, tensile properties, TGA, and DSC. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1438–1447, 2002; DOI 10.1002/app.10408     

Preparation and studying properties of polybutene‐1/thermoplastic starch blends

Starch as an inexpensive and renewable source has been used as a filler for environmental friendly plastics for about two decades. In this study, glycerol was used as a plasticizer for starch to enhance the dispersion and the interfacial affinity in thermoplastic starch (TPS)/polybutene‐1(PB‐1) blend. PB‐1 was melt blended with TPS using a single screw extrusion process and molded using injection molding process to investigate the rheological and mechanical properties of these blends. Rheological properties were studied using a capillary rheometer, and the Bagley's correction was performed. Mechanical analysis (stress–strain curves) was performed using Testometric M350‐10 kN. The rheological properties showed that the melt viscosity of the blend is less than that of PB‐1, and the flow activation energy at a constant shear stress of the blend increases with increasing glycerol content in the blend. The mechanical experiments showed that both stress and strain at break of the blends are less than that of PB‐1, whereas the Young's modulus of the most blends is higher than that of PB‐1 which confirms the filling role of TPS in the blend. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Processing and properties of thermoplastic starch and its blends with sodium alginate

Viscosity measurements were carried out on corn starch (CS) and CS–sodium alginate (SA) suspensions at low levels of SA [1 to 10% (w/w)], as a function of temperature. The addition of SA caused the granular CS gelatinization process to occur at a lower onset temperature. CS and CS–SA mixtures were extruded in single‐ and twin‐screw extruders, with 15% glycerol and different water contents. Processing of plasticized CS–SA mixtures required lower temperatures, which is consistent with the viscosity results. Homogeneous and flexible extrudates were obtained by processing in a twin‐screw extruder. Samples in the composition range between 0 and 10% (w/w) SA were examined using tensile tests as a function of water content. Mechanical properties were dependent on the water content and on the SA composition. A significant increase in the Young's modulus value was observed for the blend containing 1% SA. Dynamic mechanical analysis was carried out for CS and CS–SA blends. Two transitions were detected in the temperature range –80 to 150°C. Scanning electron microscopy was used to examine the morphology of the extruded samples. The surfaces of the films were homogeneous, which demonstrated that the CS granules in all samples were characteristically destructured under the conditions used in processing. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 412–420, 2001     

Shrinking rate of conducting grains in HCl–protonated polyaniline,polypyrrole, and polypyrrole/polyaniline blends with their thermal aging

The dc electrical conductivity (σ) of HCl‐protonated polyaniline, polypyrrole, and their blends was measured from 80 to 300 K for thermal aging times between approximately 0 and 600 h. The thermal aging took place at 70°C under room atmosphere. The change of σ with the temperature (T) and the decrease of σ with the thermal aging time (t) are consistent with a granular metal type structure, in which conductive grains are randomly distributed into an insulating matrix. Aging makes the grains shrink in a corrosion‐like process. From σ = σ(T) measurements the ratio s/d, where s is the average separation between the grains and d their diameter, as well as the rate d(s/d)/dt of their decrease with t were calculated. These revealed that the conductive grains consist of a shell, in which aging proceeds at a decreasing rate, and a central core, which is consumed at a much slower rate. Our measurements not only permitted the estimation of the shell thickness, which lies between 0 and 5 Å, but also gave quantitative information about the quality of the shells and the cores from their aging rates. The shells are consumed with an average rate of d(s/d)/dt = 6.6 × 10^?4 (h^?1), which is about 5 times greater than the more durable cores. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 117–122, 2005     

Phase behavior, morphology and interfacial structure in thermoset/thermoplastic elastomer blends of poly(propylene glycol)-type epoxy resin and polystyrene–b-polybutadiene

Thermoset/thermoplastic elastomer (TPE) blends of poly(propylene glycol) (PPG)-type epoxy resin (ER) and a diblock copolymer, polystyrene–b-polybutadiene (SB, with 30% styrene content), were prepared using 4,4′-diaminodiphenylmethane (DDM) as curing agent. The miscibility and thermal transition behavior of DDM-cured ER/SB blends were investigated by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The existence of three separate glass transitions, which are independent of the blend composition, indicates that SB is immiscible with DDM-cured ER. Neither the PS block nor the PB block exhibits miscibility with the cured ER. There exist three phases in the blends: a PS microphase, an ER-rich phase and a PB microphase. The phase structure and morphology of the ER/SB blends were studied using both scanning and transmission electron microscopy (SEM and TEM); a variety of morphologies were observed, depending on the blend composition. For the blends with 5 and 10 wt% SB, SB domains with irregular shapes and broadly distributed sizes are dispersed in a continuous cured ER matrix. For the blends with 20–60 wt% SB, interpenetrating bicontinuous phase structures are observed. For the blends with 70 wt% and more SB, a dispersion of cured ER particles in the SB matrix is obtained. The TEM observation showed that the two phases in the blends exhibit a good interfacial adhesion. The interfacial layer between the ER and SB phases varies from 100 to 300 nm for the blend with 20 wt% SB content, SB micelles are formed surrounding the SB domains in the ER matrix. Small-angle X-ray scattering (SAXS) experiments reveal that the SB diblock polymer still exhibits a lamellar microphase structure within the SB phase and the long spacing of lamellae nearly does not change in the blends. The SB diblock copolymer is microphase separated in the macroscopically phase separated ER/SB blends.     

Preparation and characterization of composite membranes using blends of SPEEK/PBI with boron phosphate

In this contribution composite membranes have been prepared from acid-base polymer blend and solid inorganic proton conductive boron phosphate (BPO₄). The blends are composed of sulfonated polyether-ether ketone (SPEEK) as the acidic component and polybenzimidazole (PBI) as the basic component. The contents of solid BPO₄ in the composite membrane varied from 10 to 40 wt%. The conductivity of the composite membranes was measured by impedance spectroscopy at room temperature. The conductivity of the composite membranes was found to increase with the incorporation of boron phosphate particles into blend membranes. The highest conductivity of 6 mS/cm was found for composite membrane at room temperature. The membranes were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and FTIR which showed acid-base interaction in the blend membranes and also confirmed the presence of solid BPO₄ into the composite membranes. These membranes show good perspective in the membrane fuel cell applications.