The Experts below are selected from a list of 120 Experts worldwide ranked by ideXlab platform
Kyu Ho Chae - One of the best experts on this subject based on the ideXlab platform.
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polymerization of n 4 azidocarbonyl phenyl maleimide and n 4 n phenoxycarbonylamino phenyl maleimide polymers containing Aromatic Isocyanate precursors
Polymer, 1999Co-Authors: Ji Young Chang, Kyu Ho ChaeAbstract:Abstract N -[4-(Azidocarbonyl)phenyl]maleimide ( 3 ) and N -[4-( N ′-phenoxycarbonylamino)phenyl]maleimide ( 5 ) were polymerized and copolymerized with methyl methacrylate (MMA) or acrylic acid (AA) by initiation with AIBN. The resultant polymers were to have Aromatic isocyanato groups when heated. In the differential scanning calorimetry measurement, the polymers from monomer 3 showed a strong and broad exotherm around 130°C. Thermogravimetric analysis also showed a weight decrease corresponding to the elimination of nitrogen at that temperature. The formation of isocyanato groups was confirmed by infra-red measurement with varying the cell temperature. The coupling reaction of the polymer with N -4-(nitrophenyl)- L -prolinol, resulting in the formation of urethane bonds, was carried out in a quantitative yield. The crosslinked films from copolymers of 5 and MMA or AA were obtained when heated above 200°C. The cured films were insoluble in common organic solvents. With the copolymers with AA it was expected that carboxylic groups would react with isocyanato groups generated from urethane units when heated. The copolymer was degraded above 150°C. After curing, its thermal stability improved dramatically, no weight loss being observed up to 300°C.
Ji Young Chang - One of the best experts on this subject based on the ideXlab platform.
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polymerization of n 4 azidocarbonyl phenyl maleimide and n 4 n phenoxycarbonylamino phenyl maleimide polymers containing Aromatic Isocyanate precursors
Polymer, 1999Co-Authors: Ji Young Chang, Kyu Ho ChaeAbstract:Abstract N -[4-(Azidocarbonyl)phenyl]maleimide ( 3 ) and N -[4-( N ′-phenoxycarbonylamino)phenyl]maleimide ( 5 ) were polymerized and copolymerized with methyl methacrylate (MMA) or acrylic acid (AA) by initiation with AIBN. The resultant polymers were to have Aromatic isocyanato groups when heated. In the differential scanning calorimetry measurement, the polymers from monomer 3 showed a strong and broad exotherm around 130°C. Thermogravimetric analysis also showed a weight decrease corresponding to the elimination of nitrogen at that temperature. The formation of isocyanato groups was confirmed by infra-red measurement with varying the cell temperature. The coupling reaction of the polymer with N -4-(nitrophenyl)- L -prolinol, resulting in the formation of urethane bonds, was carried out in a quantitative yield. The crosslinked films from copolymers of 5 and MMA or AA were obtained when heated above 200°C. The cured films were insoluble in common organic solvents. With the copolymers with AA it was expected that carboxylic groups would react with isocyanato groups generated from urethane units when heated. The copolymer was degraded above 150°C. After curing, its thermal stability improved dramatically, no weight loss being observed up to 300°C.
Marwah Rayung - One of the best experts on this subject based on the ideXlab platform.
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comparative study of Aromatic and cycloaliphatic Isocyanate effects on physico chemical properties of bio based polyurethane acrylate coatings
Polymers, 2020Co-Authors: Nurul Huda Mudri, Luqman Chuah Abdullah, Min Min Aung, Mek Zah Salleh, Dayang Radiah Awang Biak, Marwah RayungAbstract:Crude jatropha oil (JO) was modified to form jatropha oil-based polyol (JOL) via two steps in a chemical reaction known as epoxidation and hydroxylation. JOL was then reacted with Isocyanates to produce JO-based polyurethane resin. In this study, two types of Isocyanates, 2,4-toluene diIsocyanate (2,4-TDI) and isophorone diIsocyanate (IPDI) were introduced to produce JPUA-TDI and JPUA-IPDI respectively. 2,4-TDI is categorised as an Aromatic Isocyanate whilst IPDI is known as a cycloaliphatic Isocyanate. Both JPUA-TDI and JPUA-IPDI were then end-capped by the acrylate functional group of 2-hydroxyethyl methacrylate (HEMA). The effects of that Isocyanate structure were investigated for their physico, chemical and thermal properties. The changes of the functional groups during each synthesis step were monitored by FTIR analysis. The appearance of urethane peaks was observed at 1532 cm−1, 1718 cm−1 and 3369 cm−1 while acrylate peaks were detected at 815 cm−1 and 1663 cm−1 indicating that JPUA was successfully synthesised. It was found that the molar mass of JPUA-TDI was doubled compared to JPUA-IPDI. Each resin showed a similar degradation pattern analysed by thermal gravimetric analysis (TGA). For the mechanical properties, the JPUA-IPDI-based coating formulation exhibited a higher hardness value but poor adhesion compared to the JPUA-TDI-based coating formulation. Both types of jatropha-based polyurethane acrylate may potentially be used in an ultraviolet (UV) curing system specifically for clear coat surface applications to replace dependency on petroleum-based chemicals.
R. Selvaraj - One of the best experts on this subject based on the ideXlab platform.
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Studies on the evaluation of the performance of organic coatings used for the prevention of corrosion of steel rebars in concrete structures
Progress in Organic Coatings, 2009Co-Authors: R. Selvaraj, M. Selvaraj, S.v.k. IyerAbstract:Abstract Corrosion of steel rebars in reinforced concrete constructions, particularly those located in marine environments and industrially polluted areas is one of the major problems baffling the construction industry all over the world including India. A suitable protective coating to rebar is found to improve the durability of such structures under aggressive exposures. The performance of a few polymeric coatings based on different resins such as acrylic polyol-Aromatic Isocyanate, polyester polyol-Aromatic Isocyanate, acrylic resin and epoxy–silicone–polyamide containing ordinary Portland cement or flyash as extenders and titanium dioxide and zinc phosphate as main pigments on rebar in concrete has been evaluated using mechanical strength tests and accelerated corrosion tests. It is observed that, of the 16 coating formulations, four have been found to perform well as effective and durable coatings.
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Characterization and Development of Organic Coatings for Steel Rebars in Concrete
Portugaliae Electrochimica Acta, 2009Co-Authors: R. Selvaraj, B. BhuvaneshwariAbstract:Corrosion of the embedded steel reinforcements (rebars) in concrete is the major reason for the deterioration of concrete structures. One of the effective methods of overcoming this serious problem is by applying a barrier coating to the steel rebars. The barrier coating on steel rebars isolates the steel from the immediate environment and also acts as an insulator to prevent the corrosion. Four different coatings have been formulated using resins such as epoxy silicone-polyamide, polyester polyol-Aromatic Isocyanate, and acrylic polyol-Aromatic Isocyanate. These formulations consist of either ordinary portland cement (OPC) or fly ash as extender (pozzolanic pigments) and titanium dioxide (TiO 2) and zinc phosphate as the main pigment. All these coatings have been studied for their barrier protection and other mechanical properties. Evaluation study of these coatings include Electrochemical Impedance Spectroscopy (EIS), chemical resistance tests and mechanical tests such as flexibility, impact resistance, adhesion, hardness and abrasion resistance, etc., as per ASTM standards and the results are discussed elaborately. It has been concluded from this study that the epoxy siliconepolyamide resin based coating formulation shows good mechanical properties in addition to the barrier protection to the steel rebars from the corrosive environments.
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Studies on the Evaluation of the Performance of two Types of Polyurethane Coatings on Steel Rebars for the Prevention of Corrosion in Concrete Structures
Portugaliae Electrochimica Acta, 2007Co-Authors: R. Selvaraj, M. Selvaraj, S.v.k. IyerAbstract:The performance of two resin combinations, such as acrylic polyol – Aromatic Isocyanate and polyester polyol – Aromatic Isocyanate as durable and effective rebar coatings for steel in concrete has been examined by studying their mechanical properties and by using accelerated tests such as salt spray test and electrochemical impedance spectroscopy. It is found that polyester polyol-Aromatic Isocyanate combination performs better than acrylic polyol-Aromatic Isocyanate combination. Incorporation of fly ash in the coating is found to influence the performance of the coating.
Sankaraiah Subramani - One of the best experts on this subject based on the ideXlab platform.
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thermal decomposition behavior of blocked diIsocyanates derived from mixture of blocking agents
Macromolecular Research, 2005Co-Authors: Sankaraiah SubramaniAbstract:To improve the performance and reduce raw material costs, blocked Isocyanates were prepared with mixture of blocking agents in many industries. Three blocked Isocyanates (adducts) namely e-caprolactam/benzotriazole-blocked 4,4′-diphenylmethane diIsocyanate (MDI), toluene-2,4-diIsocyanate (TDI) and 4,4′-dicyclohexylmethane diIsocyanate (H12MDI) were synthesized. Six reference adducts were also prepared by blocking MDI, TDI, and H12MDI with e-caprolactam (e-CL) or benzotriazole. The reactions were carried out in acetone medium and dibutyltin dilaurate (DBTDL) was used as a catalyst. The progress of the blocking reaction was monitored by IR spectroscopy. De-blocking temperatures (dissociation temperatures) of these adducts were studied using DSC and TGA and the results were correlated. As expected, the thermal analysis data showed that de-blocking temperature of blocked Aromatic Isocyanates was lower than that of the blocked aliphatic Isocyanates. The low de-blocking temperature of blocked Aromatic Isocyanate could be due to electron withdrawing benzene ring present in the blocked Isocyanates. It was also found that benzotriazole-blocked adducts de-blocked at higher temperature compared with e-CL-blocked adducts.
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Thermal decomposition behavior of blocked diIsocyanates derived from mixture of blocking agents
Macromolecular Research, 2005Co-Authors: Sankaraiah SubramaniAbstract:To improve the performance and reduce raw material costs, blocked Isocyanates were prepared with mixture of blocking agents in many industries. Three blocked Isocyanates (adducts) namely ε-caprolactam/benzotriazole-blocked 4,4′-diphenylmethane diIsocyanate (MDI), toluene-2,4-diIsocyanate (TDI) and 4,4′-dicyclohexylmethane diIsocyanate (H_12MDI) were synthesized. Six reference adducts were also prepared by blocking MDI, TDI, and H_12MDI with ε-caprolactam (ε-CL) or benzotriazole. The reactions were carried out in acetone medium and dibutyltin dilaurate (DBTDL) was used as a catalyst. The progress of the blocking reaction was monitored by IR spectroscopy. De-blocking temperatures (dissociation temperatures) of these adducts were studied using DSC and TGA and the results were correlated. As expected, the thermal analysis data showed that de-blocking temperature of blocked Aromatic Isocyanates was lower than that of the blocked aliphatic Isocyanates. The low de-blocking temperature of blocked Aromatic Isocyanate could be due to electron withdrawing benzene ring present in the blocked Isocyanates. It was also found that benzotriazole-blocked adducts de-blocked at higher temperature compared with ε-CL-blocked adducts.
