Showing papers on "Differential scanning calorimetry published in 2015"
TL;DR: These nanocomposite hydrogels with unprecedented stretchability, toughness, and self-healing have been developed by in situ polymerization of acrylamide with the presence of exfoliated montmorillonite layers as noncovalent cross-linkers and are demonstrated to fully heal by dry-reswell treatments.
Abstract: Nanocomposite hydrogels with unprecedented stretchability, toughness, and self-healing have been developed by in situ polymerization of acrylamide with the presence of exfoliated montmorillonite (MMT) layers as noncovalent cross-linkers. The exfoliated MMT clay nanoplatelets with high aspect ratios, as confirmed by transmission electron microscopy (TEM) and X-ray diffraction (XRD) results, are well dispersed in the polyacrylamide matrix. Strong polymer/MMT interaction was confirmed by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The effective cross-link densities of these hydrogels are estimated in the range of 2.2–5.7 mol m–3. Uniaxial tensile tests showed a very high fracture elongation up to 11 800% and a fracture toughness up to 10.1 MJ m–3. Cyclic loading–unloading tests showed remarkable hysteresis, which indicates energy dissipation upon deformation. Residual strain after cyclic loadings could be recovered under mild conditions, with the recovery exten...
273 citations
TL;DR: In this article, the ionic conductivity of polymeric gel electrolyte membranes has been found to increase with increasing concentration of IL and attains a maximum value of 2 × 10−3 S cm−1 at 30 °C and ∼3 × 10 −2 S cm −1 at 130 °C.
Abstract: Ion conducting polymer gel electrolyte membranes based on polymer poly(vinylidene fluoride-co-hexafluoropropylene) PVdF-HFP, ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide BMIMTFSI with and without the Li-salt (having the same anion i.e. the TFSI− anion) have been synthesized. Prepared membranes have been characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared (FTIR), differential scanning calorimetry, thermogravimetric analysis (TGA) and complex impedance spectroscopic techniques. Incorporation of IL in the polymer PVdF-HFP/polymer electrolyte (i.e. PVdF-HFP + 20 wt% LiTFSI) changes different physicochemical properties such as melting temperature (Tm), glass transition temperature (Tg), thermal stability, degree of crystallinity (Xc), and ionic transport behaviour of these materials. The ionic conductivity of polymeric gel electrolyte membranes has been found to increase with increasing concentration of IL and attains a maximum value of 2 × 10−3 S cm−1 at 30 °C and ∼3 × 10−2 S cm−1 at 130 °C. A high total ionic transference number >0.99 and the cationic transference number (tLi+) ∼ 0.22 with a wider electrochemical window (ECW) ∼ 4.0–5.0 V for the polymer gel electrolyte membrane containing higher loading of IL (∼70 wt% of IL) have been obtained. Temperature dependent ionic conductivity obeys Arrhenius type thermally activated behaviour.
225 citations
TL;DR: In this paper, the thermal conductivity and thermal diffusivity of the solid/liquid phase change linear n-alkanes were measured simultaneously by the transient multi-current hot wire technique at atmospheric pressure in the range 258-348 K. The same set-up was used to measure the liquid and the solid states at different electrical currents.
224 citations
TL;DR: In this paper, a paraffin-nanomagnetite (Fe3O4) composites (PNMC) were prepared by a dispersion technique to enhance their thermal properties.
221 citations
TL;DR: In this paper, high-temperature properties of boron nitride platelets were systematically evaluated through TGA in combination with differential scanning calorimetry (DSC) X-Ray Diffraction (XRD) studies confirmed the hexagonal graphitic-like structure of the material, while Fourier-Transform Infrared Spectroscopy (FT-IR) indicated the active vibration modes related to the B-N bond.
214 citations
TL;DR: The results of all the aforementioned studies distinctly confirmed that DETA-APP was an effective flame-retardant curing agent for EP.
Abstract: A novel multifunctional organic–inorganic hybrid was designed and prepared based on ammonium polyphosphate (APP) by cation exchange with diethylenetriamine (DETA), abbreviated as DETA-APP. Then DETA-APP was used as flame-retardant curing agent for epoxy resin (EP). Curing behavior, including the curing kinetic parameters, was investigated by differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). The flame retardance and burning behavior of DETA-APP cured EP were also evaluated. The limiting oxygen index (LOI) value of DETA-APP/EP was enhanced to 30.5% with only 15 wt % of DETA-APP incorporated; and the UL-94 V-0 rating could be easily passed through with only 10 wt % of the hybrid. Compared with DETA/EP, the peak-heat release rate (PHRR), total heat release (THR), total smoke production (TSP), and peak-smoke production release (SPR) of DETA-APP/EP (15 wt % addition), obtained from cone calorimetry, were dropped by 68.3, 79.3, 79.0, and 30.0%, respectively, suggesting excellent...
195 citations
TL;DR: In this article, a microencapsulated phase change materials (MEPCM) based on paraffin wax core and poly(methyl methacrylate-co-methyl acrylate) shell with nano alumina (nano-Al2O3) inlay was synthesized through emulsion polymerization.
191 citations
TL;DR: In this article, structural, thermal, morphological and optical properties of ZnO nanoparticles were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Ultraviolet-Visible spectro-graph (UV-VVC), and Raman spectroscopic analysis.
189 citations
TL;DR: In this paper, a lauric acid-based phase change nanocomposites with chemically functionalized graphene nanoplatelets and measured its thermal conductivity using transient hot wire method.
182 citations
TL;DR: In this article, a novel kind of graphene oxide-modified poly(melamine-formaldehyde) (PMF) microcapsule containing phase change material (microPCM) n-dodecanol was prepared by in situ polymerization.
Abstract: A novel kind of graphene oxide-modified poly(melamine-formaldehyde) (PMF) microcapsule containing phase change material (microPCM) n-dodecanol was prepared by in situ polymerization. Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used to study the chemical structure of graphene oxide (GO) and microPCMs, respectively. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate the morphology of GO and microPCMs, respectively. The thermal properties of microPCMs were studied by differential scanning calorimetry (DSC), thermal constant analysis (TCA) and thermal cycling tests. The FTIR and XRD results indicate that the phase change material n-dodecanol is encapsulated in the GO/PMF composite shell, and there is no chemical reaction between them. The SEM results show that the prepared GO-modified PMF microPCMs are spherical particles with a smooth surface. The DSC results indicate that the phase change temperature and the latent heat of microPCMs with 1 wt% of GO are 26.40 °C and 125.2 J g−1, respectively. The thermal conductivity of GO/microPCMs with 4 wt% GO increases by 66.29%, compared with that of microPCMs without GO according to the TCA results. Moreover, the thermal cycling tests show that the prepared microPCMs possess a good thermal stability. The GO-modified PMF microPCMs are sure to have great potential applications in thermal energy storage.
174 citations
TL;DR: In this paper, the relative rates of these copolymerization were monitored using in situ attenuated total reflectance infra-red (ATR-IR) spectroscopy.
TL;DR: The blend film exhibited a more homogeneous and compact structure compared with that of the collagen film, as observed from scanning electron microscopy and atomic force microscopy, and the tensile strength, ultimate elongation and hydrophilicity of the blend film were superior to those of the pure collagen film.
TL;DR: In this article, a systematic study has been carried out to provide a better understanding of the ionic transport mechanism in polymerized ionic liquids (PolyILs) with different pendant groups.
Abstract: Polymerized ionic liquids (PolyILs) are promising candidates for energy storage and electrochemical devices applications. Understanding their ionic transport mechanism is the key for designing highly conductive PolyILs. By using broadband dielectric spectroscopy (BDS), rheology, and differential scanning calorimetry (DSC), a systematic study has been carried out to provide a better understanding of the ionic transport mechanism in PolyILs with different pendant groups. The variation of pendant groups results in different dielectric, mechanical, and thermal properties of these PolyILs. The Walden plot analysis shows that the data points for all these PolyILs fall above the ideal Walden line, and the deviation from the ideal line increases upon approaching the glass transition temperature (Tg). The conductivity for these PolyILs at their Tgs are much higher than the usually reported value ∼10–15 S/cm for polymer electrolytes, in which the ionic transport is closely coupled to the segmental dynamics. These r...
TL;DR: In this paper, an in-depth comparative study of poly(propylene-2,5-furan dicarboxylate) (PPF) is performed.
TL;DR: In this paper, a new paraffin/expanded vermiculite composite phase change material (PCM) was tailor-made as aggregate for developing lightweight thermal energy storage cement-based composites (LW-TESCCs).
TL;DR: In this article, the X-ray diffraction (XRD) patterns of the fibres showed a skewed amorphous halo, whereas the differential scanning calorimetry (DSC) results revealed an apparent crystallinity of 6-8% for the 0.4 and 1-μm fibres and 0.2% crystallinity for the 4.3-mm fibres.
Abstract: Tough fibrous membranes for smoke filtration have been developed from recycled polyethylene terephthalate (PET) bottles by solution electrospinning. The fibre thicknesses were controlled from 0.4 to 4.3 μm by adjustment of the spinning conditions. The highest fibre strength and toughness were obtained for fibres with an average diameter of 1.0 μm, 62.5 MPa and 65.8 MJ m−3, respectively. The X-ray diffraction (XRD) patterns of the fibres showed a skewed amorphous halo, whereas the differential scanning calorimetry (DSC) results revealed an apparent crystallinity of 6–8% for the 0.4 and 1 μm fibres and 0.2% crystallinity for the 4.3 μm fibres. Heat shrinkage experiments were conducted by exposing the fibres to a temperature above their glass transition temperature (Tg). The test revealed a remarkable capability of the thinnest fibres to shrink by 50%, which was in contrast to the 4.3 μm fibres, which displayed only 4% shrinkage. These thinner fibres also showed a significantly higher glass transition temperature (+15 °C) than that of the 4.3 μm fibres. The results suggested an internal morphology with a high degree of molecular orientation in the amorphous segments along the thinner fibres, consistent with a constrained mesomorphic phase formed during their rapid solidification in the electric field. Air filtration was demonstrated with cigarette smoke as a model substance passed through the fibre mats. The 0.4 μm fibres showed the most effective smoke filtration and a capacity to absorb 43× its own weight in smoke residuals, whereas the 1 μm fibres showed the best combination of filtration capacity (32×) and mechanical robustness. The use of recycled PET in the form of nanofibres is a novel way of turning waste into higher-value products.
TL;DR: In this paper, a shape-stabilized phase change material (PCM) was developed by impregnation of hydrated salts into expanded graphite (EG) and further coated with paraffin wax.
TL;DR: In this paper, the microcellular structure and crystallization behavior of polylactide composite foams were characterized using scanning electron microscopy and differential scanning calorimetry, and the results showed that the presence of nanoclay and talc together with the expedited crystallization enhanced the PLA foams morphology with a finer and more uniform cell structure.
TL;DR: In this article, a phosphorous/nitrogen-containing reactive phenolic derivative (DOPO-HPM) was synthesized via the addition reaction between 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10oxide and N-(4-hydroxyphenyl) maleimide (HPM).
TL;DR: In this paper, a bio-based epoxy monomer, diglycidyl ester of 2,5-furandicarboxylic acid (DGF), was synthesized for the first time from the renewable 2.5-furandic-arboxyl acid (FDCA).
Abstract: A bio-based epoxy monomer, diglycidyl ester of 2,5-furandicarboxylic acid (DGF) was synthesized for the first time from the renewable 2,5-furandicarboxylic acid (FDCA). For comparison study, its petroleum-based counterpart, diglycidyl ester of terephthalic acid (DGT) was also prepared. Their chemical structures were confirmed in detail by 1H NMR, 13C NMR and FT-IR before they were cured by methylhexahydrophthalic anhydride (MHHPA) and poly(propylene glycol)bis(2-aminopropyl ether) (D230), respectively. The curing behaviors were investigated using differential scanning calorimetry (DSC). The thermal mechanical properties and thermal stabilities of the cured resins were evaluated using dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). Results showed that DGF displayed higher curing activity, elevated glass transition temperature and similar mechanical properties compared with those of the cured DGT. This study indicated that FDCA had a huge potential to replace the petroleum-based terephthalic acid in the synthesis of epoxy resins with satisfactory performance.
TL;DR: In this article, three typical nitramine explosives (cyclotrimethylenetrinitramine, RDX, cyclotetramethylENetetranitramines, HMX; and hexanitrohexaazaisowurtzitane, CL-20) based microcapsules were selected for the fabrication of three typical Nitramine explosive cores, and the polymer coating shell was prepared via a facile in situ polymerization of melamine and formaldehyde on the surface of explosive crystals.
TL;DR: A therapeutic DES based on ibuprofen, a non-steroidal anti-inflammatory drug (NSAID), and menthol was synthesized and its thermal behavior was analyzed by differential scanning calorimetry (DSC), providing important clues for the development of carriers for the sustainable delivery of bioactive compounds.
TL;DR: In this paper, a composite phase change materials (PCM) with expanded vermiculite with modified porous carbon layer was used for low-temperature thermal energy storage applications, and the results of FT-IR analysis and thermal cycling tests showed that the form-stable composite PCM had good chemical stability and thermal reliability after 200Âmelting/freezing cycles.
TL;DR: The study highlights the importance of investigating and correlating drug polymer miscibility and molecular interactions by various approaches for successful formulation of amorphous solid dispersions.
TL;DR: In this article, a poly(e-caprolactone-co-lactide) (PCLLA) rubbery layer was formed via the lignin-initiated ring opening copolymerization of an e-caproleactone/L-Lactide mixture.
Abstract: Poly(lactide) (PLA)–lignin composites were fabricated by blending lignin-g-rubber-g-poly(D-lactide) copolymer particles and commercial poly(L-lactide) (PLLA) in chloroform. To synthesize the copolymer, a poly(e-caprolactone-co-lactide) (PCLLA) rubbery layer was formed via the lignin-initiated ring opening copolymerization of an e-caprolactone/L-lactide mixture, followed by the formation of poly(D-lactide) (PDLA) outer segments via the polymerization of D-lactide. The PDLA segments may contribute to strong interfacial interactions between lignin-rubber-PDLA and PLLA matrix by stereocomplexation, which was observed using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR) and wide angle X-ray scattering (WAXS). The quasi-random structure of PCLLA and the formation of the outer PDLA segments were characterized by nuclear magnetic resonance (NMR). A Tg of ∼−36 °C for PCLLA was detected by DSC, which confirms the rubbery character of the synthesized copolymer. The resulting renewable and biodegradable composites exhibited a six-fold increase of elongation at break and a simultaneous improvement in their tensile strength and Young's modulus, though to a lesser extent. Light scattering, WAXS, small angle X-ray scattering (SAXS) and scanning electron microscope (SEM) studies suggested that good lignin dispersion, rubber-initiated crazing and strong filler/matrix interactions due to stereocomplexation are the effective mechanisms behind the excellent mechanical performance of these composites.
TL;DR: In this paper, the temperature dependence of Δhm° for both the α- and α-crystal polymorphs of PLLA were determined, by combining differential scanning calorimetry and X-ray diffraction.
TL;DR: In this article, shape-stabilized fatty acid eutectics and diatomite composites were prepared by absorbing liquid fatty acid EUTectics into diatomites, and the thermal properties of the composites are measured by differential scanning calorimetry (DSC).
TL;DR: The effects of specific drug-polymer interactions (ionic or hydrogen-bonding) on the molecular mobility of model amorphous solid dispersions (ASDs) were investigated and an increase in strength of interaction translated to higher crystallization onset temperature and a decrease in extent of crystallization.
Abstract: The effects of specific drug-polymer interactions (ionic or hydrogen-bonding) on the molecular mobility of model amorphous solid dispersions (ASDs) were investigated. ASDs of ketoconazole (KTZ), a weakly basic drug, with each of poly(acrylic acid) (PAA), poly(2-hydroxyethyl methacrylate) (PHEMA), and polyvinylpyrrolidone (PVP) were prepared. Drug-polymer interactions in the ASDs were evaluated by infrared and solid-state NMR, the molecular mobility quantified by dielectric spectroscopy, and crystallization onset monitored by differential scanning calorimetry (DSC) and variable temperature X-ray diffractometry (VTXRD). KTZ likely exhibited ionic interactions with PAA, hydrogen-bonding with PHEMA, and weaker dipole-dipole interactions with PVP. On the basis of dielectric spectroscopy, the α-relaxation times of the ASDs followed the order: PAA > PHEMA > PVP. In addition, the presence of ionic interactions also translated to a dramatic and disproportionate decrease in mobility as a function of polymer concentration. On the basis of both DSC and VTXRD, an increase in strength of interaction translated to higher crystallization onset temperature and a decrease in extent of crystallization. Stronger drug-polymer interactions, by reducing the molecular mobility, can potentially delay the crystallization onset temperature as well as crystallization extent.
TL;DR: In this paper, a solid polymer electrolyte (SPE) was prepared by a ball milling method followed by a hot pressing process, and the morphology, ionic conductivity, thermal and mechanical properties of the SPE were also examined.
TL;DR: Two new crown ether clathrates possessing unusual high-temperature ferroelectric phase-transition behaviors, cyclohexyl ammonium 18-crown-6 tetrafluoroborate (or perchlorate) and Hcha, are displayed and proven to have reversible structural phase transitions by variable-tem temperature PXRD measurements and temperature evolutions of Raman bands.
Abstract: Molecular ferroelectrics with high-temperature reversible phase-transition behaviors are very rare and have currently become one of the hotspots in the field of ferroelectric materials. Herein we display two new crown ether clathrates possessing unusual high-temperature ferroelectric phase-transition behaviors, cyclohexyl ammonium 18-crown-6 tetrafluoroborate (or perchlorate), [Hcha-(18-crown-6)]+ [BF4]− (1) and [Hcha-(18-crown-6)]+[ClO4]− (2) (Hcha = protonated cyclohexyl ammonium). We have proven their reversible structural phase transitions by variable-temperature PXRD measurements and temperature evolutions of Raman bands. Both clathrates exhibit clear ferroelectric phase transitions at about 397 and 390 K, respectively, revealed by the thermal anomalies of differential scanning calorimetry (DSC) measurements, together with abrupt dielectric anomalies in the heating and cooling processes. The measurements on ferroelectric properties using the single crystals showed optimized spontaneous polarization (...