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Utracki L.A.,Industrial Materials Institute of Canada
Polymer Degradation and Stability | Year: 2010

The Pressure-Volume-Temperature (PVT) of polystyrene (PS), polyamide-6 (PA-6) and their clay-containing polymeric nanocomposites (CPNC) were determined at T = 300-600 K and P = 0.1-190 MPa, thus in the molten, glassy and semicrystalline phase. The melt and glass behavior was interpreted following the Simha-Somcynsky (S-S) cell-hole free volume theory while that of the semicrystalline phase using S-S and the Midha-Nanda-Simha-Jain (MNSJ) cell theory describing crystalline quantum interactions. The theoretical analysis yielded two sets of the interaction parameters, one from the S-S and the other from the MNSJ model. The derivative properties: the compressibility, κ, and thermal expansion coefficient, α, were computed as functions of T, P and clay content, w. These functions, crossing several transition regions, were significantly different for the amorphous PS than for the semicrystalline PA-6. The isobaric PS plots of κ and α vs. T detected secondary transitions at Tβ/Tg ≈ 0.9 ± 0.1 and at Tc/Tg = 1.2 ± 0.1. Addition of clay severely affected the vitreous phase (physical aging). In PA-6 systems the behavior was distinctly different than in PS, viz. κ = κ(T) followed a similar function across the melting zone, while α = α(T) dependencies were dramatically different for the solid and molten phase. The theoretical functions in reduced variables over(κ, ̃) = κ P* = over(κ, ̃) (over(T, ̃), over(P, ̃)) ; over(α, ̃) = α T * = over(α, ̃) (over(T, ̃), over(P, ̃)) provided good basis for explanation of the observed dependencies. Crown Copyright © 2009. Source


Yang D.,Industrial Materials Institute of Canada
Journal of Power Sources | Year: 2011

Thin films of manganese oxides have been grown by the pulsed laser deposition (PLD) process on silicon wafer and stainless steel substrates at different substrate temperatures and oxygen gas pressures. By proper selection of processing parameters such as temperature and oxygen pressure during the PLD process, pure crystalline phases of Mn 2O 3, Mn 3O 4 as well as amorphous phase of MnO x were successfully fabricated as identified by X-ray diffraction. The pseudo-capacitance behaviours of these different phases of manganese oxides have also been evaluated by the electrochemical cyclic voltammetry measured in 0.1 M Na 2SO 4 aqueous electrolyte at different scan rates. Their specific current and capacitance determined by electrochemical measurements were compared and the results show that crystalline Mn 2O 3 phase has the highest specific current and capacitance, while the values for crystalline Mn 3O 4 films are the lowest. The specific current and capacitance values of the amorphous MnO x films are lower than Mn 2O 3 but higher than Mn 3O 4. The specific capacitance of Mn 2O 3 films of 120 nm thick reaches 210 F g -1 at 1 mV s -1 scan rate with excellent stability and cyclic durability. This work has demonstrated that PLD is a very promising technique for screening high performance active materials for supercapacitor applications due to its excellent flexibility and capability of easily controlling chemical composition, microstructures and phases of materials. © 2011 Elsevier B.V. All rights reserved. Source


Laforgue A.,Industrial Materials Institute of Canada
Journal of Power Sources | Year: 2011

Poly(3,4-ethylenedioxythiophene) (PEDOT) nanofibers were obtained by the combination of electrospinning and vapor-phase polymerization. The fibers had diameters around 350 nm, and were soldered at most intersections, providing a strong dimensional stability to the mats. The nanofiber mats demonstrated very high conductivity (60 ± 10 S cm-1, the highest value reported so far for polymer nanofibers) as well as improved electrochemical properties, due to the ultraporous nature of the electrospun mats. The mats were incorporated into all-textile flexible supercapacitors, using carbon cloths as the current collectors and electrospun polyacrylonitrile (PAN) nanofibrous membranes as the separator. The textile layers were stacked and embedded in a solid electrolyte containing an ionic liquid and PVDF-co-HFP as the host polymer. The resulting supercapacitors were totally flexible and demonstrated interesting and stable performances in ambient conditions. © 2010 Elsevier B.V. Source


Li H.,Industrial Materials Institute of Canada | Huneault M.A.,Universite de Sherbrooke
Journal of Applied Polymer Science | Year: 2011

This article investigates the structure and properties of thermoplastic starch/PLA blends where the TPS phase is plasticized by sorbitol, glycerol, and glycerol/sorbitol mixtures. The blends were prepared using a twin-screw extruder where starch gelatinization, water removal, and dispersion of TPS into a PLA matrix were carried out sequentially. The plasticizers were added to starch in the first stage of the extruder to allow complete starch gelatinization. The PLA was added at mid-extruder and thoroughly mixed with the TPS. The plasticizer concentration was varied from 30 to 42% and the TPS content was varied from 27 to 60% on a weight basis. In all investigated blends, the PLA formed the continuous phase and the TPS was the dispersed phase. The viscosity, blend morphology, tensile mechanical properties as well as the thermal properties of the materials were measured. It was found that the glycerol/sorbitol ratio has an important effect on the blend properties. Finer blend morphologies, higher tensile strength and modulus but lower crystallization rate were found for the sorbitol plasticized blends. © 2010 Wiley Periodicals, Inc. Source


Laforgue A.,Industrial Materials Institute of Canada
Journal of Materials Chemistry | Year: 2010

Conductive PEDOT nanofiber mats were obtained by the electrospinning of oxidant fibers and subsequent vapour-phase polymerization of the EDOT monomer. The mats presented high conductivities as well as unprecedented resistive heating properties. Electrically controlled colour-changing textiles were produced by coating thermochromic inks on the PEDOT mats and triggering the colour change by applying current to the mat. © 2010 The Royal Society of Chemistry. Source

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