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Sealing gas mains using anaerobic joint injection and spray sealants / F. Lott in ADHESIVES AGE, Vol. 40, N° 9 (08/1997)
[article]
Titre : Sealing gas mains using anaerobic joint injection and spray sealants Type de document : texte imprimé Auteurs : F. Lott, Auteur ; S. Brown, Auteur ; A. F. Douglas, Auteur ; D. E. Keene, Auteur ; S. J. Peacock, Auteur Année de publication : 1997 Article en page(s) : p. 22-25 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Amines Une amine est un composé organique dérivé de l'ammoniac dont certains hydrogènes ont été remplacés par un groupement carboné. Si l'un des carbones liés à l'atome d'azote fait partie d'un groupement carbonyle, la molécule appartient à la famille des amides. Découvertes en 1849, par Wurtz les amines furent initialement appelées alcaloïdes artificiels.
On parle d'amine primaire, secondaire ou tertiaire selon que l'on a un, deux ou trois hydrogènes substitués.
Par exemple, la triméthylamine est une amine tertiaire, de formule N(CH3)3.
Typiquement, les amines sont obtenues par alkylation d'amines de rang inférieur. En alkylant l'ammoniac, on obtient des amines primaires, qui peuvent être alkylées en amines secondaires puis amines tertiaires. L'alkylation de ces dernières permet d'obtenir des sels d'ammonium quaternaire.
D'autre méthodes existent : 1. Les amines primaires peuvent être obtenues par réduction d'un groupement azoture, 2. Les amines peuvent aussi être obtenues par la réduction d'un amide, à l'aide d'un hydrure, 3. L'amination réductrice permet l'obtention d'amines substituées à partir de composés carbonylés (aldéhydes ou cétones), 4. Les amines primaires peuvent être obtenues par la réaction de Gabriel.
Chélates
Dépôt par pulvérisation
Joints anaérobies
Joints d'étanchéité
Peroxydes
Polyacryliques
Radicaux libres (chimie)
Tuyaux de gazIndex. décimale : 668.3 Adhésifs et produits semblables Résumé : Considerable expertise has been developed in the last 15 years by Chemence to produce economic anaerobic methods of sealing joints in cast iron and steel distribution mains. There are hundreds of thousands of kilometers of cast iron gas mains still in existence. The BG Transco (British Gas) distribution system in the United Kingdom alone consists of over 50 000 km of main, whereas in the United States there are over 100 000 km. Traditional sealing techniques involve encapsulation of the joint in two-part polyurethane and epoxy resins or clamping the joint with a rubber gasket. These techniques are expensive, and, if the joint is not cleaned properly, unreliable. Accordingly, a technique that was cheap and easy to apply was needed. The anaerobic injection method was developed to meet this need.
Injection proved to be extremely successful, and by 1990 more than 90% of all joints in the United Kingdom were sealed by this method. Chemence is the sole supplier to BG Transco; it has successfully sealed over 750 000 joints.
Recently a report from Cornell University has shown that anaerobic repairs can have a life expectancy of well over 30 years. Anaerobic injection is now extensively used in North America.
Anaerobic sealants can also be sprayed into a gas main so that up to 100 m of pipeline can be treated in one application. The success rate is not as high as with the injection method, but this approach represents a highly cost effective way of joint sealing, particularly for programmed repairs.Note de contenu : - CHEMICAL PRINCIPLES OF ANAEROBIC SEALING
- PERFORMANCE PRINCIPLES
- ADVANTAGES OF ANAEROBIC SEALING TECHNOLOGY FOR "FID AND FIX" REPAIR
- ENVIRONMENTAL FACTORS : Temperature - Vibration
- SUITABLE JOINTS : Lead/yarn joints - Mechanical joints
- APPLICATION METHODS : Difficult joints - Special situationsEn ligne : https://drive.google.com/file/d/1ez7PbrBu8iK7VFNI5SjyjhCokBIOIcLQ/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=20452
in ADHESIVES AGE > Vol. 40, N° 9 (08/1997) . - p. 22-25[article]Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité 001079 - Périodique Bibliothèque principale Documentaires Exclu du prêt The infuence of metal complex dye stability and dye interaction in aqueous solution on within-skin, within-pack and pack to pack colour variation / W. R. Dyson in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 63, N° 1 (01-02/1979)
[article]
Titre : The infuence of metal complex dye stability and dye interaction in aqueous solution on within-skin, within-pack and pack to pack colour variation Type de document : texte imprimé Auteurs : W. R. Dyson, Auteur Année de publication : 1979 Article en page(s) : p. 1-5 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Chélates
Chrome
Cobalt
Colorants -- Stabilité
Complexes métalliques
Cuirs et peaux -- Teinture
Cuivre
Fer
Ions cuivre
Ions métalliques
Solutions aqueuses (chimie)Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : - Chemical constitution of leather dyes: atomic absorption analysis
- Stability of iron complex dyes to EDTA
- Stability of iron cpmplex dyes to metal ions
- Effect of EDTA and cupric ions on the dyeing performance of iron complex dyes
- Effect of sequestrants on chromium, cobalt and copper complexes
- Interaction between iron complex and copper complex dyes in aqueous solution
Résumé: It has been shown that iron complex and many copper complex dyes are readily decomposed by sequestrants. In addition, iron complex dyes are readily decomposed by cupric ions. Hue changes occur on dye decomposition and these can give rise to unlevelness and colour variation in dyeing. Certain combinations of iron and copper complex dyes are unstable in aqueous solution at 60°C and this can result in pack to pack colour variation. Colour fastness may not be predictable from comparisons of manufacturer's ratings if decomposition has occured.Note de contenu : - Chemical constitution of leather dyes: atomic absorption analysis
- Stability of iron complex dyes to EDTA
- Stability of iron cpmplex dyes to metal ions
- Effect of EDTA and cupric ions on the dyeing performance of iron complex dyes
- Effect of sequestrants on chromium, cobalt and copper complexes
- Interaction between iron complex and copper complex dyes in aqueous solutionEn ligne : https://drive.google.com/file/d/1OmU6R0VvyAquCOIP7KrJ2ntUyFruey0m/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=30173
in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 63, N° 1 (01-02/1979) . - p. 1-5[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 007119 - Périodique Bibliothèque principale Documentaires Disponible UV damage to hair and the effect of antioxidants and metal chelators / Keith R. Millington in INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Vol. 42, N° 2 (04/2020)
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Titre : UV damage to hair and the effect of antioxidants and metal chelators Type de document : texte imprimé Auteurs : Keith R. Millington, Auteur ; J. M. Marsh, Auteur Année de publication : 2020 Article en page(s) : p. 174-184 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Analyse spectrale
Antioxydants
Chélates
Cheveux -- Effets du rayonnement ultraviolet
Fluorescence
Photodétérioration
Radicaux libres (chimie)Index. décimale : 668.5 Parfums et cosmétiques Résumé : - OBJECTIVE : To study the effects of addition of a redox metal, copper, antioxidants and metal chelators on the formation of free radicals in natural white Caucasian hair subsequently exposed to UV light. Three different methods, electron paramagnetic resonance (EPR), a fluorescent probe for hydroxyl radical formation (terephthalate) and free radical photoyellowing, were used. These methods utilized different UV sources and reaction conditions, and so can give insights into the different mechanisms of action occurring during UV oxidation of hair. In addition, this study demonstrates how antioxidants and chelators can be screened to determine whether they can protect hair from UV damage.
- RESULTS : The three methods gave somewhat different results, illustrating the importance of reaction conditions and wavelength on the photochemical mechanisms, and the efficacy of additives to influence these reactions. EPR results showed that N-acetylcysteine (NAC) pre-treatment eliminated the intensity of the signal because of sulphur and carbon free radicals in white hair both before and after exposure to UVB radiation. Doping the hair with copper ions had no effect on the intensity of the EPR signal under dry conditions. Terephthalate fluorescent probe data showed that under wet conditions, irradiation of white hair with UVA produced significant amounts of hydroxyl radicals. Pre-treatment of hair with NAC reduced the number of •OH radicals produced by natural white hair compared to an untreated control. In contrast to the EPR result, white hair doped with copper ions produced significantly higher levels of •OH radicals under wet conditions. It appears that the ability of copper ions to catalyse the photogeneration free radicals in hair is highly dependent on water content. Photoyellowing data showed a benefit for oxalic acid but no difference for NAC and an increase in yellowing for EDTA.
- CONCLUSION : The micro-EPR and terephthalate fluorescent probe methods are both effective techniques to study production of free radicals by hair exposed to UV light under wet and dry conditions, respectively. Both assays are simple methods for determining the effectiveness of potential protective hair treatments against UV damage, but because they assess free radical damage under dry vs wet conditions, the chemistry created on UV exposure is different. This gives insights into mechanism of action, but results may not be consistent between the two methods for actives added for reduction of UV damage. NAC pre-treatment did reduce free radical generation in UV-exposed hair under both wet and dry conditions. Photoyellowing data are more complicated as it is a less direct measure of UV damage and is highly dependent on irradiation source. Using UVB irradiation is experimentally convenient but may not be appropriate, because UVB wavelengths comprise only 0.3% of terrestrial sunlight. The photochemistry of hair exposed to sunlight involves concurrent photobleaching and photoyellowing processes and is far more complex. Under UVB irradiation conditions, oxalic acid showed a yellowing benefit.Note de contenu : - MATERIALS AND METHODS : Chemical treatments of hair tresses - EPR spectroscopy - Terephthalate fluorescence assay for hydroxyl (OH) radicals in UVA-exposed hair - Photoyellowing experiments - Colour measurement
- RESULTS AND DISCUSSION : EPR studies - Terephthalate fluorescence assay for hydroxyl (OH) radicals - Colour changes and photoyellowingDOI : https://doi.org/10.1111/ics.12601 Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=34508
in INTERNATIONAL JOURNAL OF COSMETIC SCIENCE > Vol. 42, N° 2 (04/2020) . - p. 174-184[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 21862 - Périodique Bibliothèque principale Documentaires Disponible