1,721,122 research outputs found
Preparation and characterization of new functional materials by chemical modification of natural polysaccharides
No full textWater extraction and degradation of a sterically hindered phenolic antioxidant in polypropylene films
No full textWater extraction of the sterically hindered phenolic antioxidant Irganox 1010 from three polypropylene based polymeric films has been studied in isothermal conditions at 40, 50 and 70 °C. The films made of isotactic polypropylene and two different heterophasic polypropylene/ethylene–propylene monomers copolymers (PP/EPM copolymers) were immersed in closed water baths under nitrogen atmosphere in order to minimise the oxidative process. The amounts of antioxidant that have left the films and are dissolved in the water bath have been monitored over time by HPLC analysis and faster extraction kinetics were observed from the polymers than from the homopolymer. No appreciable amounts of Irganox 1010 were found in the extraction water at any time, whereas its degradation by-products were found by LC/MS analysis in the extraction water.
The experimental extraction kinetics from the three polymers were compared with the theoretical curves based on the Fick's diffusion equations solved both for a semi-infinite (degradation reaction faster than extraction) and a finite system (no degradation reaction) and Irganox 1010 was demonstrated to be extracted by water from polypropylene based material faster than predictable only on the basis of the values of its coefficient of diffusion in the polymers and of partition between water and polymer
Water extration and degradation of a sterically hindered phenolic antioxidant in polypropylene films
No full textChemical Methods for Gelatin Crosslinking: A Review
No full textChemical methods so far experimentally investigated for gelatin crosslinking have been summarized with special emphasis on the reaction mechanisms. Advantages and disadvantages of all reactants have been reported in relation to the significant properties of the final applicative field
Modification of surface and mechanical properties of polyethylene by photo-initiated reactions
No full textLow density polyethylene thin films were crosslinked in the bulk and on the surface by means of photo-initiated reactions. The purpose of these experiments was to study if there is a direct relationship between the distribution of crosslinks in the depth of the films and the mechanical properties of the films themselves. By bulk treatment with a PI1 photoinitiator and a dimethacrylate, samples with enhanced Young's modulus values were obtained. The addition of an inorganic filler had no significant influence on the rate of the crosslinking reaction, but resulted in an enhancement of the oxygen barrier of the treated films. Samples with enhanced modulus and hydrophilicity were obtained by hot-surface treatment with a PI2 photoinititator and multifunctional allylic and acrylic monomers. (C) 2003 Elsevier Ltd. All rights reserved
Uso di diazo derivati per l’innesto di gruppi funzionali sulla superficie di film di polietilene
No full textStudio della reazione della gelatina con esametilen-1,6-diisocianato
No full text1,6-hexamethylene diisocyanate and dimethylsolfoxide were exploited as crosslinker agent and reaction solvent, respectively in the crosslinking of gelatine. The effect of the diisocianate concentration on the crosslinking yield was studied by selective extraction with hot water of the treated gelatine. All produced materials were characterised by infrared spectroscopy, thermogravimetric analysis, electron dispersion analysis and electron microscopy investigation. High crosslinking yields and good thermal stability were found under all investigated conditions
Luminescent Bis-benzoxazolyl-stilbene as Molecular Probe for Polypropylene Films Deformation
No full textPoly(propylene) (PP) films containing different concentrations of bis(benzoxazolyl)stilbene (BBS) have been prepared by melt processing. We demonstrate that the emission characteristics of PP films depend on BBS concentration and polymer deformation. A well-defined excimer band is observed with more than 0.2 wt.-% of BBS, conferring to the film a green luminescence. During drawing (130 degrees C) the PP reorganisation breaks the BBS excimer-type arrangement, leading to the prevalence of the blue emission of the single molecules. We have efficiently applied the photophysics of this commercial stilbene derivative to the production of powerful tools acting as an internal probe for PP deformation
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