Epoxy resins and their curing agents : a review / Risbabh Dwivedi in PAINTINDIA, Vol. LXVIII, N° 6 (06/2018)  

[article]  inPAINTINDIA > Vol. LXVIII, N° 6 (06/2018) . - p. 53-60 Titre : Epoxy resins and their curing agents : a review Type de document : texte imprimé Auteurs : Risbabh Dwivedi, Auteur ; Rupanshu Rastogi, Auteur Année de publication : 2018 Article en page(s) : p. 53-60 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Epoxydes Réticulants Index. décimale : 667.9 Revêtements et enduits Résumé : Epoxy resin are the reactive intermediates used to form thermoset polymers by reacting with a hardener. Epoxy resin are characterized by the presence of three membered cyclic ether group. The most widely used epoxy resins are diglycidyl ether of bisphenol A (DGEBA). Epoxy resins have a high degree of chemical resistance, toughness, rigidity also epoxy resins have outstanding adhesion over a variety of substrates which make them very useful in the coating as well as adhesives. The good adhesion is also responsible for corrosion resistance. This paper discusses various types of epoxy resins, the curing agents for these epoxy resins, their properties and applications. Note de contenu : - CLASSIFICATION OF EPOXY RESINS : Tri functional epoxy resins - Tetra functional epoxy - Multi-functional epoxy-novolac - Epoxide equivalent weight - CURING OF EPOXY RESINS : Amine hardeners - Reactions with acid anhydrides - Mercaptan (polysulphide and polymercaptans) curing agent - Reaction with isocyanates - Reaction with methylol and methylol ether groups - Advantages and disadvantages of curing agent used En ligne : https://drive.google.com/file/d/1MvFjOh5qLCZ8m_0SdfJw9-A87nkFcdw3/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=31033 [article]

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Synthesis of cardanol based epoxy resin for high solids UV curable coatings using bio based reactive diluent : review / Rupanshu Rastogi in PAINTINDIA, Vol. LXIX, N° 1 (01/2019)  

[article]  inPAINTINDIA > Vol. LXIX, N° 1 (01/2019) . - p. 55-63 Titre : Synthesis of cardanol based epoxy resin for high solids UV curable coatings using bio based reactive diluent : review Type de document : texte imprimé Auteurs : Rupanshu Rastogi, Auteur ; Risbabh Dwivedi, Auteur Année de publication : 2019 Article en page(s) : p. 55-63 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Cardanol Diluants Epoxydes Haut extrait sec Polymères -- Synthèse Revêtements -- Additifs Revêtements -- Séchage sous rayonnement ultraviolet Index. décimale : 667.9 Revêtements et enduits Résumé : With the increase in demand for petrochemical resources resulting in continuous depletion and increased price it's a great challenge for coating industry to look down palliatives based on renewable and sustainable materials which are ecofriendly and non-hazardous. The paper describes some important routes of developing liquid epoxy resin from Cardanol which can be made UV curable by converting into acrylates using bio based reactive diluent based on ricinolic acid(castor oil). Hence the developed product is solvent free and used for high solids coating minimizing the environmental pollution. This dark brown-colored viscous liquid obtained from shel Is of the cashew nut can be utilized fora number of polymerization reactions due to its reactive phenolic structure and a meta-substituted unsaturated al iphatic chain. The product can be implemented in primer coats of metal and wood replacing the conventional Bisphenol-A based epoxy system. The negative impact of BPA on human health and the environnent necessarily implies the el imination of BPA especially in food contact materials. Therefore there is an increasing interest within the chemical industry for non-harmful aromatic substituents to BPA, especially for the synthesis of epoxy polymers. Thus, cardanol could be an interesting substitute to BPA in some polymers such as epoxy polymers. Note de contenu : - Routes of cardanol epoxy synthesis - UV curing - Synthesis of cardanol epoxy acrylate (oligomer resin) - Reactive diluent from ricinoleic acid - Fig. 1 : CNSL origin - Fig. 2 : Physical characteristics of CNSL - Fig. 3 : Chemical composition of CNSL - Fig. 4 : Chemical structure of cardanol - Fig. 5 : Scheme for malenisation of cardanol - Fig. 6 : Scheme for epoxidation of malenised cardanol - Fig. 7 : Chemical structure of cardanol novolac resin - Fig. 8 : Scheme for preparation of cardanol novolac epoxy - Fig. 9 : Reaction scheme of cardanol and polycardanol solid line : reaction route A ; dotted line : reaction route B - Fig. 10 : Synthesis of polyols form cardanol - Fig. 11 : Coating process and schematic principle of UV curing - Fig. 12 : Schematic representation of the chemical processes occurring in EB and UV curing (radical mechanism). B : backbone of the resin molecule or the reactive diluent ; PI : photo-initiator ; R. : radicals initiating the propagation reaction - Fig. 13 : Reaction of cardanol epoxy novalac with acrylic acid to bring unsaturation in the molecule - Fig. 14 : Trifunctional cardanol epoxy acrylate oligomer prepared by reaction of the product obtained from Fig. 6 with acrylic acid - Fig. 15 : Reaction of epoxidied cardanol from Fig. 8 with acrylic acid - Fig. 16 : Examples of "alpha-cleavage type" and non-cleavable "electron transfer-hydrogen abstraction type" - Fig. 17 : Synthesis of biobased reactive diluent En ligne : https://drive.google.com/file/d/1u05gduYzEnUrj_jxK3USXMPGtu5A3AyX/view?usp=share [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=31939 [article]

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Versatility of polyurethane polymers : a review / Rupanshu Rastogi in PAINTINDIA, Vol. LXIX, N° 4 (04/2019)  

[article]  inPAINTINDIA > Vol. LXIX, N° 4 (04/2019) . - p. 90-100 Titre : Versatility of polyurethane polymers : a review Type de document : texte imprimé Auteurs : Rupanshu Rastogi, Auteur ; Risbabh Dwivedi, Auteur Année de publication : 2019 Article en page(s) : p. 90-100 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Polyuréthanes Index. décimale : 668.9 Polymères Résumé : Polyurethanes, because of their versatility are materials of choice which can satisfy multi-purpose design objectives. They can be tailor-made to fit into applications where advanced performance standards respond to the expectations and needs of sustainable development. The applications of polyurethane coatings, foams, fibers, moldings, and elastomers demonstrate the versatility of urethane chemistry and the creativity of polymer researchers. Clearly, modification of the raw materials and production process through proper methods can produce PUs that is suitable for varied specific applications. The paper discusses the synthesis of polyurethane polymers, the raw materials used and types. The general manufacturing process has also been included for better understanding. Furthermore, information is provided on the environmental friendliness of the PUs and its advancement. Note de contenu : - Polyurethane synthesis : Raw materials requird - Isocyanates - Polyols - Catalysts - Chain extenders - Surfactants - Versatile reactions of diisocyanates - Thermoplastic polyurethanes - Coatings, adhesives, sealants and elastomers (CASE) - Foamed polyurethanes : Rigid polyurethane fomas - Flexible polyurethane - Waterborne polyurethanes - Polyurethanes ionomers - The manufacturing process : Polymer reactions - Processing - Manufacturing of polyurethane resin dispersions - Acetone process - Prepolymer mixing process - Melt emulsification process - Applications : Advantages - Disadvantages and limitations - Automotive - Furniture - Construction - Thermal insulation - Footwear - Recent development - Fig. 1 : Worldwide PU production and an estimated forecast up to 2020 - Fig. 2 : Urethane group - Fig. 3 : Condensation of a polyisocyanate and a polyol - Fig. 4 : Isocyanates monomers - Fig. 5 : Comparison of basic polyol structures - Fig. 6 : Primary addition reactions of isocyanate with (a) amine, (b) water, (c) alcohol, (d) carboxylic acid, (e) urea - Fig. 7 : Secondary addition reactions of isocyanate with (a) polyurethane, (b) polyurea and (c) polyamide - Fig. 8 : Self-addition reactions of isocyanate - Fig. 9 : Scanning electron micrograph showing the closed cells of rigid foam - Fig. 10 : Scanning electron micrograph showing the open cells of flexible foam - Fig. 11 : A diagram depicting the manufacturing processes used to create rigid polyurethane foam insulation - Fig. 12 : Prepolymer mixing process - Fig. 13 : Scheme for prepolymer mixing process - Fig. 14 : Scheme for melt emulsification process - Fig. 15 : Property madrix of polyurethanes - Fig. 16 : Scheme for manufacturing non isocyanate polymers - Fig. 17 : General methods of producing non-isocyanate polyurethanes - Fig. 18 : Scheme for developing polyols based on vegetable oils - Table 1 : The NCO equivalent weight can be calculated from the % NCO (equation 2) and the OH equivalent weight from either the %OH or the OH number (equation 3) - Table 2 : Basic raw materials for polyurethane synthesis En ligne : https://drive.google.com/file/d/1jrpbjAqBxEgJq30u0rm-hDOt2c-8DiWp/view?usp=share [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=32632 [article]

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