An overview of the science and art of encapsulated pigments : Preparation, performance and application / Benjamin Tawiah in COLORATION TECHNOLOGY, Vol. 138, N° 3 (06/2022)  

[article]  inCOLORATION TECHNOLOGY > Vol. 138, N° 3 (06/2022) . - p. 224-247 Titre : An overview of the science and art of encapsulated pigments : Preparation, performance and application Type de document : texte imprimé Auteurs : Benjamin Tawiah, Auteur ; Benjamin K. Asinyo, Auteur ; Charles Frimpong, Auteur ; Ebenezer K. Howard, Auteur ; Raphael K. Seidu, Auteur Année de publication : 2022 Article en page(s) : p. 224-247 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Complexation (chimie) Couches minces multicouches Dispersions et suspensions Encapsulation Essais (technologie) Evaluation Pigments Polymérisation Séparation de phases Sol-gel, Procédé Index. décimale : 667.2 Colorants et pigments Résumé : A successfully encapsulated pigment requires dispersants, pigment and a dispersion medium to build a thin layer of polymer over individual pigment particles. The stability of encapsulated dispersion is aided by the absorption of stabilising molecules on the surface. The stabilising molecules function by steric hindrance or Coulomb-repulsion forces, which prevent the encapsulated pigments from advancing too close to each other for attractive forces to cause agglomeration. Unlike flocculation, agglomeration results in a cementitious network structure that is not easily redispersed by shear forces, hence the need for effective dispersion of encapsulated pigment intended for engineering applications. Besides dispersion forces, the quality of pigment dispersion, the pigment particle size, pigment density, viscosity of the dispersion, and the method of producing the pigment microcapsules, also affect the efficiency and the quality of encapsulated pigment dispersions. This article, therefore, provides up-to-date information on the various pigment encapsulation methods (with specific emphasis on phase separation, in situ polymerisation, emulsion and mini-emulsion polymerisation, the sol-gel method, inclusion complexation and layer-by-layer assembly), and also reviews the performance, the evaluation/test methods and applications of encapsulated pigments. This review provides important insight into the science and art of encapsulated pigment preparation for pigment dispersion technologists, researchers and consumers of pigment products in different fields of endeavour. Note de contenu : - METHODS OF ENCAPSULATION : Preparation of encapsulated pigment dispersion - Physico-chemical methods - Chemical methods - INCLUSION COMPLEXATION - PERFORMANCE OF ENCAPSULATED PIGMENT DISPERSIONS : Stability - Rheological behavior - COLOUR PERFORMANCE OF ENCAPSULATED PIGMENT DISPERSION - EVALUATION METHODS FOR ENCAPSULATED PIGMENT DISPERSION - APPLICATIONS OF ENCAPSULATED PIGMENT DISPERSION : Emerging applications of encapsulated pigments - Table 1 : Encapsulation methods suitable for different ranges of capsule size - Table 2 : Selected studies in in situ polymerisation - Table 3 : Advantages and limitations of some conventional encapsulation methods applicable different types of pigments - Table 4 : Test methods for evaluating encapsulated pigment dispersion - Table 5 : Application of encapsulated pigments DOI : https://doi.org/10.1111/cote.12597 En ligne : https://onlinelibrary.wiley.com/doi/epdf/10.1111/cote.12597 Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=37853 [article]

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Oxidising degradation of Valonia extract and utilisation of the products. Part 1. Oxidising degradation of Valonia extract and characterisation of the products / Bi Shi in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 84, N° 6 (11-12/2000)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 84, N° 6 (11-12/2000) . - p. 258-262 Titre : Oxidising degradation of Valonia extract and utilisation of the products. Part 1. Oxidising degradation of Valonia extract and characterisation of the products Type de document : texte imprimé Auteurs : Bi Shi, Auteur ; Ying Di, Auteur ; Youjie He, Auteur ; Lijiang Song, Auteur ; Yu Zhao, Auteur Année de publication : 2000 Article en page(s) : p. 258-262 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Aluminium trivalent Chrome trivalent Complexation (chimie) Couleur Extraits de plantes Oxydation Peroxyde d'hydrogène Le peroxyde d'hydrogène (H2O2), communément appelé eau oxygénée ou encore perhydrol (appellation industrielle), est un composé chimique liquide et visqueux, aux puissantes propriétés oxydantes (il est aussi réducteur). C'est donc un agent blanchissant efficace qui sert de désinfectant et (à haute concentration) d'oxydant ou monergol dans les fusées spatiales. Poids moléculaires Résistance chimique Tanins végétaux Valonia et constituants Valonia est un genre d'algues vertes de la famille des Valoniaceae. La taille d'une seule cellule pluri-nucléée peut atteindre 2 cm chez certaines espèces. (Wikipedia) Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : Oxidation using H2O2 brings about degradation of valonia extract. Three typical products with novel properties were obtained when 20%, 40% and 60% H2O2 (conc. 50%) were used. Determinations indicated that the oxidising reaction leads to lowering of molecular weight, lightening of colour, improving of acid and salting-out resistances and increasing of hydrophilic groups, carboxyl in particular. The more interesting results are that penetrating rates of the degraded products in pelt are markedly accelerated and that the alkali resistance of complex compounds of the products and Cr(III) or Al(III) is considerably increased. The effects above are enhanced with increasing offer of H20.The conditions for oxidising degradation are described and the potentials of utilising the products are discussed. Note de contenu : - EXPERIMENTAL PROCEDURES : Oxidising degradation of valonia extract - Determination of molecular weight distribution - Colour determination - Characterisation of structure - Acid resistance and salting-out effect determinations - Determination of tanning property - Complexing characteristics with Al(III) and Cr (III) - RESULTS AND DISCUSSION - Table 1 : Molecular weight distributions of oxidised degradation products of valonia extracts - Table 2 : The colour of valonia extract and its oxidised degradation products - Table 3 : Precipitate ratios (%) of valonia extract and its oxidised degradation products at different pH* - Table 4 : Precipitate ratios (%) of valonia extract and its oxidised degradation products in NaC1 solution - Table 5 : The tanning properties of valonia extract and its oxidised degradation products* - Table 6 : Precipitating pH of complex solutions of oxidised degradation products and Cr(III) - Table 7 : Precipitating pH of complex solutions of oxidised degradation products and Al(III) En ligne : https://drive.google.com/file/d/1MNgqR-q-yGLMFjML87uHVZ7aRinbwt3x/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=40815 [article]

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Polyacrylic acid (PAA)/Zn2+ complex films fabricated on steel substrate via one-step assembly for corrosion protection / Ru Yan in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 21, N° 1 (01/2024)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 21, N° 1 (01/2024) . - p. 267-280 Titre : Polyacrylic acid (PAA)/Zn2+ complex films fabricated on steel substrate via one-step assembly for corrosion protection Type de document : texte imprimé Auteurs : Ru Yan, Auteur ; Xiang Gao, Auteur ; Wei He, Auteur ; Yan Wang, Auteur ; Houyi Ma, Auteur Année de publication : 2024 Article en page(s) : p. 267-280 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Acide polyacrylique Acier L'acier est un alliage métallique utilisé dans les domaines de la construction métallique et de la construction mécanique. L'acier est constitué d'au moins deux éléments, le fer, très majoritaire, et le carbone, dans des proportions comprises entre 0,02 % et 2 % en masse1. C'est essentiellement la teneur en carbone qui confère à l'alliage les propriétés du métal qu'on appelle "acier". Il existe d’autres métaux à base de fer qui ne sont pas des aciers comme les fontes et les ferronickels par exemple. Adhésion Anticorrosifs Anticorrosion Complexation (chimie) Ions zinc Métaux -- Revêtements protecteurs Revêtement de conversion Index. décimale : 667.9 Revêtements et enduits Résumé : The eco-friendly PAA/Zn2+ conversion coatings, composed of PAA-Zn2+ complex and ZnO/Zn(OH)2, have been prepared by taking advantage of coordination-driven assembly method for suppressing steel corrosion. Because of high affinity of PAA for steel surface and various metal ions, metal ions-assisted organic molecule assembly strategy used to construct chemical conversion film on metal surface has been extended to the design and construction of polyelectrolyte–metal complex conversion coating. In this work, some film properties associated closely with film formation time containing corrosion resistance, surface microstructures, and chemical compositions were carefully investigated by using electrochemical measurements, morphologies tests, and spectra analysis and possible film-forming mechanism of PAA/Zn2+ film was proposed. The highest charge transfer resistance (Rct = 24,960 ohm cm2) was recorded for PAA/Zn2+ film based on EIS, which is about 30 times higher than that of the bare steel. And minimum corrosion current density (icorr = 1.01 × 10-7 A cm-2) was obtained for PAA/Zn2+ film from polarization curves, which is only 3.34% of that obtained from bare steel. Herein, the PAA/Zn2+ conversion coatings constructed between 30 and 60 min present outstanding corrosion resistance performance and the protection efficiencies are greater than 90%. Furthermore, PAA/Zn2+ films have a positive effect on improvement in adhesion of epoxy coating on steel surface, which can further improve corrosion resistance of whole paint system, especially for PAA/Zn2+ films fabricated for long film formation time (e.g., 30 min and 45 min). Due to environmental friendliness, strong corrosion resistance, and good adhesion performance, PAA/Zn2+ conversion coatings are expected to be an ideal substitute for the traditional chromating process. Note de contenu : - EXPERIMENTAL : Materials and chemical reagents - Chemical conversion treatment - Epoxy primer treatment - Anticorrosion performance evaluation - Surface observation and analysis - RESULTS AND DISCUSSION : Corrosion resistance of PAA/Zn2+ conversion films - EIS tests - Polarization curves - Surface characterization - SEM and EDS analysis - Corrosion protection performance of paint system - Table 1 : Electrochemical parameters of naked steel and steel covered by PAA/Zn2+ films determined from EIS measurements - Table 2 : Corrosion electrochemical parameters for the naked steel and the modified steel by PAA/Zn2+ films in 3.5 wt% NaCl solution DOI : https://doi.org/10.1007/s11998-023-00818-y En ligne : https://drive.google.com/file/d/1nO0pvQ-ysQZzdu6BQbZUTdvFu7SoQlN1/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=40446 [article]

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