Dierential Scanning Calorimetry Research Articles

Influence of nanoparticle weight fraction on morphology and thermal properties of HDPE/SiO2 composite films

High-density polyethylene (HDPE) composite films with di erent amounts of SiO 2 nanoparticles ( 1 - 20 % vol.) were prepared by melt blending using a high-pressure thermal pressing technique. The morphological characterization, surface topology and distribution of nanoparticles in polymer matrix of nanocomposites were investigated by using Scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thermal characterization of the nanocomposites were investigated by di erential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). SEM and AFM results revealed that silica nanoparticles aggregates were distributed mainly homogeneously. The nano-fillers change supramolecular structure and surface morphology of HDPE strongly. DSC results showed addition of nano-SiO 2 particles slightly decrease the melting temperature by 3-4 degree but strongly decrease the crystallization temperature by 7-8 degree. And crystallinity degree of the HDPE decrease. The thermal stability of the composite films was measured using Thermo Gravimetric analysis (TGA). Polymer nanocomposite showed higher thermal stability as compared with pure HDPE. Composites with 20% vol. of nano-SiO 2 have maximum thermal degradation temperature of 498.4 ◦ C.

MICROENCAPSULACIÓN DE UN HIDROLIZADO PROTEÍNICO DE FRIJOL BAYO(Phaseolus vulgaris) CON ACTIVIDAD INHIBITORIA SOBRE LA ENZIMACONVERTIDORA DE ANGIOTENSINA-I MEDIANTE LIOFILIZACI ́ON

The aim of this study was to obtain microcapsules of a bayo bean protein hydrolysate (BBPH) with antihypertensive activity using Eudragit® L 30 D-55 as wall material (EGLD) through freeze-drying processing. The BBPH was obtained using sequential pepsin-pancreatin enzymatic system. The ACE-I inhibitory activity was measured using tripeptide hippurylhistidyl leucine (HHL) as model peptide. Three microcapsule formulations were prepared containing BBPH and EGLD at ratios of 1:20, 1:4 and 1:1, respectively. The physicochemical characteristics of microcapsules were evaluated by optical (OM) and scanning electronic microscopy (SEM), confocal laser scanning microscopy (CLSM), dierential scanning calorimetry (DSC), X-ray diraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). ACE-I inhibitory activity of BBPH was IC50=0.42 mg/mL. All microcapsules showed irregular shapes. The BBPH was distributed homogeneously in all formulations. The DSC and XRD analysis revealed a uniform dispersion of the BBPH and partially crystalline structures of EGLD and BBPH. The FT-IR confirmed the chemical stability of BBPH in the microcapsules. In conclusion, the EGLD microcapsules containing BBPH were prepared successfully by freeze-drying processing.

Determination of Secondary Nanostructure of Model Membrane from Local Fishes for Application in Pharmaceutical Field

As it is di cult to obtain human stratum corneum for testing the pharmacological e ect of the drugs, many researchers have tried to nd alternative membrane for this purpose, instead of the human skin. Many animal skins e.g. pig, reptile, or sh skin seem to be suitable for this purpose. Therefore this project will provide more details to help understand more deeply the structure of these alternative skins. This project is focused on the sh skin because such skin can be easily found in Germany. Two di erent techniques i.e. small and wide angle X-ray scattering (SWAXS) and di erential scanning calorimetry (DSC) have been applied for characterization of some local sh skins. The results showed that di erent skins (i.e. human stratum corneum, pig, shed snake, and sh) showed small di erences in SWAXS patterns as well as in DSC thermograms. The drug paracetamol and the surfactant sodium lauryl sulphate can penetrate into the sh skins and they can a ect a rearrangement of the inner structure which contains di erent lipids and proteins. The data are in agreement with those obtained for the shed snake skins in our previous study.

Mechanochemically Synthesized Nanocrystalline Sb2S3Particles

Nanocrystalline Sb2S3 particles have been synthesized from Sb and S powders by high-energy milling in a planetary mill using argon protective atmosphere. X-ray di raction, particle size analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, electron di raction, high resolution transmission electron microscopy, UV-VIS, and di erential scanning calorimetry methods for characterization of the prepared particles were applied. The powder X-ray di raction pattern shows that Sb2S3 nanocrystals belong to the orthorhombic phase with calculated crystallite size of about 36 nm. The nanocrystalline Sb2S3 particles are constituted by randomly distributed crystalline nanodomains (20 nm) and then these particles are forming aggregates. The monomodal distribution of Sb2S3 particles with the average hydrodynamic parameter 210 nm was obtained. The quanti cation of energy dispersive X-ray spectroscopy analysis peaks give an atomic ratio of 2:3 for Sb:S. The optical band gap determined from the absorption spectrum is 4.9 eV, indicating a considerable blue shift relative to the bulk Sb2S3. Di erential scanning calorimetry curves exhibit a broad exothermic peak between 200 and 300 ◦C, suggesting recovery processes. This interpretation is supported by X-ray di raction measurements that indicate a 23-fold increase of the crystallite size to about 827 nm as a consequence of application of high temperature process. The controlled mechanochemical synthesis of Sb2S3 nanoparticles at ambient temperature and atmospheric pressure remains a great challenge.

On Analysis of DSC Curves for Characterization of Intrinsic Properties of NiTi Shape Memory Alloys

Di erential scanning calorimetry is discussed as a tool for characterization of shape memory alloy materials with the example of Ni51at.% Ti polycrystalline material. Some inconsistencies connected with the di erential scanning calorimetry analysis results present in the contemporary literature are indicated, for example large discrepancies in the registered heats of phase transition or di erences in registered heats of forward and reverse phase transition, especially in the case of multi-stage phase transition sequences. An attempt is undertaken to explain some of the discrepancies. The overall conclusion from the present work is that forward and reverse sensible heats of phase transition are equal, and discrepancies reported in the literature are artefacts. It is recommended that as a standard practice of di erential scanning calorimetry analysis of shape memory alloy materials not only characteristic temperatures but also sensible heat of phase transition should be reported, which can be done at practically no additional cost.

Structural Changes of DPPC Bilayers Induced by Gemini Surfactant

The phospholipid gemini surfactant systems are promising agents for construction of lipoplexes for DNA delivery systems in gene therapy. In this work the in uence of a gemini surfactant 1,1′-(1,6-hexan)bis3octyloxymethylimidazolium di-chloride) (IMI_Cl_C6_C8) on the structure and phase behaviour of aqueous suspensions of the fully hydrated phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) were characterised using small angle scattering of synchrotron radiation (SAXS), di erential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The surfactant studied caused a destabilisation of the lamellar phase typical of DPPC. Addition of the surfactant also shifted to lower temperatures and extended the range of the main phase transition

Wire Explosion Synthesis of a Sn/C Nanocomposite as an Anode Material for Li Secondary Batteries

As a top-down approach for nanomaterial synthesis, a “wire explosion in liquid media” process was applied to the preparation of a Sn/C nanocomposite as an alternative anode material for lithium secondary batteries. Using a highly-dispersed Sn nanoparticle suspension produced by electrical explosion of Sn wires in ethanol followed by gravimetric sedimentation for size separation and by addition of a carbon precursor and pyrolysis, we prepared nano-sized Sn particles embedded in a carbon matrix. The physical properties of the nano-sized Sn and its carbon composite were characterized by using scanning electron microscopy, transmission electron microscopy, X-ray diraction and dierential scanning calorimetry. The electrochemical property was analyzed by using cycled charge/discharge tests. The resulting Li storage performance of the Sn/C nanocomposite showed an initial discharge capacity of over 400 mAhg 1 and improved capacity retention of 340 mAhg 1 after 40 cycles. The simplicity and the scalability of nanocomposite synthesis provided by the “wire explosion in a liquid medium” process make this method a promising tool not only for new nanomaterial investigations but also for commercial production of nanomaterials.

Structure and Mechanical Behavior of Elastomeric Multiblock Terpolymers Containing Glassy, Rubbery, and Semicrystalline Blocks

Multiblock copolymers containing glassy poly-(cyclohexylethylene) (C), rubbery poly(ethylene-alt-propylene) (P), and semicrystalline poly(ethylene) (E) were synthesized by sequential anionic polymerization of styrene, isoprene, and buta-diene followed by catalytic hydrogenation. The resulting CECP-CEC (denoted XPX) and CECP (XP) multiblock copolymers each contain 50 vol % of P and equal amounts of C and E. These materials have been studied by dynamic mechanical spectroscopy (DMS), transmission electron microscopy (TEM), small- an wide-angle X-ray scattering (SAXS and WAXS), di!erential scanning calorimetry (DSC), and tensile deformation to characterize the morphology, phase behavior, and mechanical properties. Microphase separation in these compounds is induced by crystallization of Eand/or chemical incompatibility between the three blocks, leading to a new type of morphology which contains continuous region of P and continuous region ofmicrophase-separated X, resulting inmechanically resilientmaterials.Highmolecular weight block copolymers microphase separate with two di!erent length scales associated with segregation between C and E and X and P. These structural features produce a nonclassical scaling relationship for the C!E domain spacing, d ! N0.31, where N is the degree of polymerization of CEC portion. The role of semicrystalline E domains during uniaxial deformation has been exposed withWAXS experiments, which support a two-stepmechanisminvolving recoverable and nonrecoverable deformation to di!erent extents.more » Strain hardening is observed in double-anchored XPX, but not in single-anchored XP, at large tensile strains.« less

Structural Investigation of Rapidly Quenched FeCoPtB Alloys

Two sets of Fe52ixCoxPt28B20 (x = 0‐26 at.%) and Fe60ixCoxPt25B15 (x = 0‐40 at.%) alloys were prepared in the form of ribbons by the rapid quenching technique. Structure of the samples was characterized by Mossbauer spectroscopy and X-ray diraction. In the as-quenched alloys the amorphous phase coexisted with the fcc-(Fe,Co)Pt disordered solid solution. Dierential scanning calorimetry measurements performed in the range 50‐720 ‐ C revealed one or two exothermal peaks. The magnetically hard ordered L10 (Fe,Co)Pt and magnetically soft (Fe,Co)2B nanocrystalline phases were formed due to thermal treatment of the alloys. The influence of Co content on the structure of the as-quenched and heated alloys was studied.

Properties of Polyacrylic Ester Emulsion Modified with Octa(nitrophenyl)silsesquioxane (ONPS)

Octaphenylsilsesquioxane (OPS) and Octa(nitrophenyl)silsesquioxane (ONPS) were synthesized by a conventional approach. The structure was characterized by FTIR, GPC, 1H NMR and 29Si NMR. Then ONPS was added into the latex to modify polyacrylic ester (PAE) emulsion. The compatibility, mechanical and thermal properties of modified PAE emulsion were investigated through di.erential scanning calorimetry (DSC), the tensile strength tester and transmission electron microscopy (TEM) micrographs.The studies on TEM and the particle size distribution showed that the Octa(nitrophenyl)silsesquioxane particles homogeneously disperse in the emulsion at a nanometer scale. Differential scanning calorimetry showed that the addition of ONPS increased Tg of PAE emulsion significantly. The tensile strength of films increased with the addition of ONPS, but rupture elongation decreased slightly. The general properties obtained optimum when the content of ONPS was 2∼3%.

Brillouin Scattering and DSC Studies of Glass Transition Temperatures of Glucose-Water Mixtures

We studied glass transition temperatures of glucose-water mixtures by using Brillouin scattering and dierential scanning calorimetry (DSC). We tted the polarized components of the Brillouin spectra measured by back scattering geometry to simple Lorentzian form and estimated the glass transition temperature from the slope of the temperature dependent Brillouin peak shift. We also measured glass transition temperatures by using DSC. The results from both experiments were consistent with each other, indicating that the Brillouin-scattering technique can be used to determine the glass transition temperature.

Curing behaviour of compatible interpenetrating polymer networks based on epoxy and methacrylated epoxy

Compatible interpenetrating polymer networks (IPNs) based on digly- cidyl ether of bisphenol A (DGEBA) and methacrylated diglycidyl ether of bisp- henol A (MADGEBA) in weight ratios of 100/0, 75/25, 50/50, 25/75 and 0/100 were blended and cured simultaneously by using dicumyl peroxide (DICUP) and hexahydrophthalic anhydride (HHPA) as curing agents. Fourier transform infra- red spectroscopy (FTIR) was employed to investigate the intermolecular inter- actions and functional group changes. Viscosity increases during crosslinking were examined with a Brook-eld viscometer. Curing exothermic peaks were studied with di†erential scanning calorimetry (DSC). The gel fractions of various IPN compositions were measured with a Soxhlet extractor. Samples thus pre- pared were checked for their compatibility by measuring glass transitions with DSC and damping peaks with rheometric dynamic spectroscopy (RDS). Experi- mental results revealed that good compatibility between components induced a network interlock, which subsequently resulted in incomplete cure of the IPN materials.