Search results for "Chemical engineering"
showing 10 items of 5892 documents
Halloysite-Based Bionanocomposites
2017
Scientific research has been invigorated by a new class of biodegradable materials as alternatives to polymers derived from fossils. Such biomaterials can also offer economic advantages because they are derived from renewable resources. Several biopolymers (gelatin, chitin, chitosan, starch, pectin, cellulose and its modified versions, etc.) have been exploited to produce films and formulations. Their use is limited because of fast degradation, predominant hydrophilic character, and, in some cases, unsatisfactory mechanical properties. However, the properties of these polymers can be improved by using inorganic fillers such as additives. Halloysite nanotube is a promising green filler for t…
Colloidal stability of halloysite clay nanotubes
2019
Abstract The colloidal stability of halloysite clay nanotubes dispersion is reviewed showing the strategy and the mechanism to obtain stable systems in water and apolar solvents. The selective modification of halloysite inner/outer surfaces can be achieved by exploiting electrostatic interactions. The adsorption of anionic surfactants onto the halloysite cavity allows generating inorganic cylindrical micelles that can be separated from the solvent. On the other hand, the functionalization of halloysite shell by positively charged surfactants drives to obtain stable water-in-oil emulsions. The interactions with ionic and nonionic polymers alters the dispersability of halloysite due to electr…
Antibacterial biopolymeric foams: Structure–property relationship and carvacrol release kinetics
2019
Abstract In this work, the feasibility of antibacterial biopolymeric foams containing carvacrol (CRV) for potential food packaging applications was investigated. Sodium bicarbonate (SB) was chosen as foaming agent and a commercial biodegradable polymer, Mater-Bi® (MB), as a matrix. MB/SB and MB/SB/CRV systems were prepared by melt mixing and the foaming process was conducted in a laboratory press. The influence of foaming agent and antibacterial additive content was investigated. The foamed samples were characterized through morphological analysis, mechanical tests and measurements of CRV release kinetics. Moreover, a mathematical model, i.e. power law model, was used to fit the release dat…
Biphenyl derivatives containing trimethylsilyl benzyl ether or oxime groups as probes for NO2 detection
2016
[EN] Four probes based in the use of a biphenyl moiety and functionalized with trimethylsilyl benzyl ether (P1 and P3) and oxime (P2 and P4) groups have been prepared and tested as optical probes for the detection of NO2. Reaction of NO2 with acetonitrile solutions of P2-P4 resulted in the formation of aldehydes 7 and 8 with a concomitant redshift of the absorption bands. Probe P2 displayed a bathochromic shift of 45 nm upon reaction with NO2 and was able to detect this poisonous gas at concentrations as low as 0.02 ppm. P2 was highly selective against NO2 and other gases (i.e. NO, CO2, H2S, SO2) and vapours of organic solvents (i.e. acetone, hexane, chloroform, acetonitrile or toluene) had…
Magnetoelectrochemistry of 4,4′-bis(dimethylamino)biphenyl and 4,4′-dinitrobiphenyl azacrown macrocyclic lactams
2005
Abstract The voltammetric behaviour at carbon fibre microelectrodes under the application of static magnetic fields of two series of macrolactams containing in their structure 4,4′-bis(dimethylamino)biphenyl or 4,4′-dinitrobiphenyl groups in MeCN solution is described. The response of 4,4′-dinitrobiphenyl receptors is dominated by two successive one-electron reduction processes at −0.9 and −1.6 V versus AgCl/Ag. 4,4′-bis(dimethylamino)biphenyl-containing receptors display two one-electron oxidations above +0.8 and +1.0 V. In both cases, a dihedral/planar interconversion precedes the second electron transfer step. Upon application of moderate (0.05–0.2 T) static magnetic fields to the electr…
Design and synthesis of biobased epoxy thermosets from biorenewable resources
2017
International audience; Biobased diepoxy synthons derived from isoeugenol, eugenol or resorcinol (DGE-isoEu, DGE-Eu and DGER, respectively) have been used as epoxy monomers in replacement of the diglycidyl ether of bisphenol A (DGEBA). Their curing with six different biobased anhydride hardeners leads to fully biobased epoxy thermosets. These materials exhibit interesting thermal and mechanical properties comparable to those obtained with conventional petrosourced DGEBA-based epoxy resins cured in similar conditions. In particular, a high Tg in the range of 90–130 °C and instantaneous moduli higher than 4.3 GPa have been recorded. These good performances are very encouraging, making these n…
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…
Bisphenol A removal from water by biomass-based carbon: isotherms, kinetics and thermodynamics studies
2018
Biomass-based carbon was modified and used as an efficient bisphenol A (BPA) sorbent. The simple and environmentally friendly modification method produced sorbent with a capacity of 41.5 mg/g. The ...
A biostable, anti-fouling zwitterionic polyurethane-urea based on PDMS for use in blood-contacting medical devices.
2020
Polydimethylsiloxane (PDMS) is commonly used in medical devices because it is non-toxic and stable against oxidative stress. Relatively high blood platelet adhesion and the need for chemical crosslinking through curing, however, limit its utility. In this research, a biostable PDMS-based polyurethane-urea bearing zwitterion sulfobetaine (PDMS-SB-UU) was synthesized for potential use in the fabrication or coating of blood-contacting devices, such as a conduits, artificial lungs, and microfluidic devices. The chemical structure and physical properties of synthesized PDMS-SB-UU were confirmed by (1)H-nuclear magnetic resonance ((1)H-NMR), X-ray diffraction (XRD), and uniaxial stress-strain cur…
Identification and quantitation of trace amounts of barbiturates with glass capillary gas chromatography
1979
Pre-chromatographic reactions are no longer a necessary evil. Equipment such as the microrefluxer now allows reproducible 7-μl-reactions to be carried out in a short time. Thus multiple derivatisations can be used together with glass capillary GC for routine identifications. The method has been succesfully applied to barbiturates. Retention data of their methyl-, allyl- and benzyl-derivatives are given. Quantitative blood level determinations are briefly discussed.