Search results for "Calorimetry"

Aqueous phase/nanoparticles interface: hydroxypropyl cellulose adsorption and desorption triggered by temperature and inorganic salts

2012

The study highlighted the main forces driving the adsorption of hydroxypropyl cellulose (HPC) onto clay nanoparticles with a disk-like shape (Laponite RD). Modeling the isothermal titration calorimetry data provided the key thermodynamic properties, which enabled us to discuss the microscopic aspects contributing to the energetic and the entropic changes of the polymer adsorption at the nanoparticle/liquid interface. We evidenced that the process is strongly enthalpy-driven and that the interactions lead to constraints of the HPC configuration at interface. The functionalized nanoparticles enhanced the polymer solubility in water expanding the one-phase area of the binodal curve. Temperatur…

Novel antimicrobial ultrathin structures of zein/chitosan blends obtained by electrospinning

2009

Abstract This paper describes the formulation, morphology and biocide properties of novel antimicrobial electrospun zein based ultrathin fiber structures. From the results, it was found that the electrospun fibers of zein can turn the material into a new strong antimicrobial ultrathin-structured system due to retention of remnant amounts of trifluoroacetic acid as determined by ATR–FTIR spectroscopy. Unfortunately, this system may be considered to yield very aggressive high acidic media due to release of the strong acid, which causes the antimicrobial behavior. Nevertheless, since biocide properties are more desirable at mild acidic conditions, blending zein with the natural antimicrobial c…

Design, characterization and in vitro evaluation of 5-aminosalicylic acid loaded N-succinyl-chitosan microparticles for colon specific delivery

2011

The objective of this study was to prepare NS-chitosan microparticles for the delivery of 5-aminosalicylic acid (5-ASA) to the colon. Microparticles can spread out over a large area of colon allowing a more effective local efficacy of 5-ASA. N-Succinyl-chitosan was chosen as carrier system because of its excellent pharmaceutical properties in colon drug targeting such as poor solubility in acid environment, biocompatibility, mucoadhesive properties, and low toxicity. It was prepared by introducing succinic group into chitosan N-terminals of the glucosamine units. 5-ASA loaded NS-chitosan microparticles were prepared using spray-drying. As a control, a matrix obtained by freeze-drying techni…

Study of the Curing Process of DGEBA Epoxy Resin Through Structural Investigation

2015

In this work, a multi-scale approach with different analytical methods is applied to study the curing process and the structural properties of a diglycidyl ether of bisphenol A (DGEBA) epoxy resin. This monomer, thermally cured using 4,4′-diaminodiphenilsulfone (DDS) as hardener, is analyzed after 10, 45, 90, and 120 min of reaction time at 180 °C to obtain information on samples with different cross-linking densities. Samples are also characterized after extraction in acetone in order to obtain structural information on the insoluble parts. For this purpose, differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), solid-state nuclear magnetic resonance (ss-NMR),…

Evaluation of Ligno Boost™ softwood kraft lignin epoxidation as an approach for its application in cured epoxy resins

2018

Abstract In this study, modification of LignoBoost™ softwood kraft lignin with epichlorhydrin in water-organic solvents media was realized. Lignin-based epoxy resins were obtained by two ways: acetone extraction of glycidylated lignin or glycidylation of the acetone soluble lignin fraction. The effect of glycidylation regimes on the yields of acetone soluble fractions, their functional composition and physical-chemical characteristics was investigated using wet chemistry methods, FTIR spectroscopy, size exclusion chromatography (SEC) and differential scanning calorimetry (DSC). The positive effect of the biphasic phase transfer catalytic system – KOH/quaternary ammonium salt – on glycidylat…

Near-infrared diffuse reflectance spectroscopy and neural networks for measuring nutritional parameters in chocolate samples.

2007

Abstract A rapid and non-destructive method has been developed for the characterization of chocolate samples based on diffuse reflectance near-infrared Fourier transform spectroscopy (DRIFTS) and artificial neural networks (ANNs). This methodology provides a potentially useful alternative to time-consuming chemical methods of analysis. To assess its utility, 36 chocolate samples purchased from the Spanish market were analyzed for the determination of the main nutritional parameters like carbohydrates, fat, proteins, energetic value and cocoa content. Direct triplicate measurements of each sample were carried out by DRIFTS. Cluster hierarchical analysis was used for selecting calibration and…

Solvation of a probe molecule by fluid supercooled water in a hydrogel at 200 K

2008

By combining electron paramagnetic resonance (EPR) measurements on a nitroxide probe and differential scanning calorimetry (DSC), we demonstrate existence of liquid supercooled water in a silica hydrogel with high hydration level down to temperatures of at least 198 K. Besides the major fraction of liquid supercooled water, a minor fraction crystallizes at about 236 K during cooling and melts at 246 K during heating. The liquid domains are of sufficient size to solvate the nearly spherical paramagnetic probe molecule TEMPO with a diameter of about 6 angstrom. Analysis of EPR spectra provides the rotational correlation time of the probe that is further used to compare the viscosity of the su…

Paper consolidation with Halloysite nanotubes. TGA, DMA and contact angle investigations

2013

A Calorimetric and Viscosimetric Study for the Characterization of Pectin Hydrogels. Application in the field of Cultural Heritage

2009

DSC AND TGA TO EVALUATE THE SELECTIVE IMPREGNATION OF WATERLOGGED ARCHAEOLOGICAL WOODS WITH POLY(ETHYLENE) GLYCOLS MIXTURES

2012

Within the cultural heritage field the wood conservation of waterlogged archaeological objects aims at preventing the collapsing of the wooden structure (upon drying) the degradation of which is related to the Taxon but also to the chemical and biological nature of the site. The refilling of the wood cavities with a consolidant, which confers robustness and stability, is an interesting strategy for the conservation methods of waterlogged archaeological objects. To this purpose, using different impregnation methods, waterlogged archaeological woods were consolidated by using aqueous mixtures of poly(ethylene) glycols with different molecular weights (PEG 400 and PEG 4000) as well as mixtures…