1,720,996 research outputs found
Development of a new calcium sulphate-based composite using alginate and chemically modified chitosan for bone regeneration
No full textIn this work we developed a novel calcium sulphate-
based composite in which the hemihydrate calcium
sulphate (CHS) can be encapsulated in a polymeric biodegradable
and biocompatible matrix, in order to retain the
structural integrity and decrease the bioresorption rate in bone
regeneration applications. Two polymers were employed to
realize this system: chitosan (Ch) and sodium alginate (Alg),
both already widely used in biotechnological and biomedical
applications. Chitosan was modified in order to obtain a
water soluble polymer, the N-succinylchitosan (sCh). The reaction
was performed with succinic anhydride in presence of
pyridine and confirmed by FT-IR and NMR analyses. Finely
ground Alg and sCh powders were mixed in different compositions
with CHS and by adding water to the powder mixture
it was obtained a mouldable paste that sets in few hours.
Thermogravimetric analyses coupled with solvent extraction
performed on the composite proved the alginate crosslinking
in the presence of CHS. Mechanical studies carried out on
composites of different compositions demonstrated that the
blend of the two polymeric components causes a substantial
synergistic reinforcement of composites. The presence of carboxylic
groups on sCh chain in addition to those of alginate
could enhance the chelating power of polysaccharide mixture.
The results obtained with morphological analyses (SEM) further
confirmed the hypotesis of the synergistic effect between
alginate and N-succinylchitosan in presence of calcium sulphate.
In vitro cytotoxicity tests proved that the developed
system was not cytotoxic. 2007 Wiley Periodicals, Inc. J
Biomed Mater Res 81A: 811–820, 200
Crosslinker effects on functional properties of alginate/N-succinylchitosan based hydrogels
No full textIn this paper, physico-chemical, mechanical and antimicrobial properties of hydrogels based on alginate/N-succinylchitosan blends crosslinked by calcium or zinc ions containing cellulose microfibers were investigated and discussed. With respect to plain alginate hydrogels, the addition of N-succinylchitosan significantly improved properties such as swelling degree and stability in saline solution. The water vapour transmission rate confirmed that all the hydrogels were able to assure a moist wound environment. Morphological analysis showed a good embedding of fibres within the zinc crosslinked hydrogels. In addition, zinc-crosslinked hydrogels evidenced antimicrobial activity against two common skin pathogenic bacteria, Staphylococcus aureus and Escherichia coli. Cytotoxicity assays proved that the amount of zinc released is slightly over the toxic level. Overall, the characteristics of the zinc-crosslinked hydrogels showed their potential interest as materials for wound dressing
Thermal oxidative stability and effect of water on gas transport and mechanical properties in PA6-EVOH films
No full textThe thermal oxidative stability and the effect of water on gas transport and mechanical properties of blends of polyamide 6 (PA6) with ethylene-co-vinyl alcohol (EVOH) and EVOH modified with carboxyl groups (EVOH-COOH) have been investigated. The presence of EVOH reduces water vapor and oxygen gas permeability of polyamide, as well as small amounts of EVOH-COOH further improve barrier properties, especially to oxygen. This has been explained in terms of improved interactions of the blend constituents in the amorphous phase, due to ionic linkages between the polyamide amino groups and the carboxyls of modified EVOH. The permeation to gases was found to increase with the amount of sorbed water. The morphology of the samples was found to have an effect on barrier properties, as the presence of EVOH causes the PA6 α crystalline form to increase, lowering the permeability to oxygen and water vapor. Mechanical properties are strongly affected by water sorption, as tensile modulus and strength decrease with increasing water content. Chemiluminescence (CL), infrared spectroscopy (FTIR), and tensile test were employed in order to assess the correlation between chemical composition and the thermal oxidative stability of the films aged at 110 °C in air. CL experiments suggest that the presence of EVOH and EVOH-COOH efficiently inhibits the formation of peroxidized species during the processing, and increases the thermal oxidative stability of the films. Infrared spectroscopy showed a build-up of carbonyl absorption in the range 1700–1780 cm−1, due to the formation of oxidation products, which is greater in the case of the pure polymer. Tensile tests on films revealed a reduction in ductility as a result of ageing for neat PA6, whereas in comparison the blends exhibit a far better long-term stability
Unsaturated alkoxy-substituted poly(p-phenylene 1,3,4-oxadiazole)s: Synthesis and chemical-physical characterization
No full textSynthesis and characterisation of new copolyesterhydrazides with thermotropic properties.
No full textA new class of poly(ester hydrazide) copolymers with liquid crystalline properties. Synthesis and characterization
No full textAlkoxy-Substituted Poly(p-phenylene 1,3,4-oxadiazole)s: Synthesis, Chemical Characterization, and Electro-Optical Properties
No full text
A new class of poly(ester hydrazide) copolymers with liquid crystalline properties. Synthesis and characterization
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