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Sultan A Nasar - One of the best experts on this subject based on the ideXlab platform.
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synthesis and properties of aromatic hyperbranched polyureas and hyperbranched copolyureas using Blocked Isocyanate monomers
2014Co-Authors: Mahalingam Vanjinathan, Sultan A NasarAbstract:diamino phenyl phenylcarbamate- an AB2- type Blocked Isocyanate monomer was synthesized. Step- growth polymerization of this monomer was found to give a hyperbranched poly (aryl-urea). The polymers were characterized by FT-IR, 1 H-NMR, TGA and DSC measurements. Molecular weights (Mw) of the polymers were determined using GPC. The polydispersity indexes were relatively narrow due to the controlled regeneration of Isocyanate functional groups for the polymerization reaction. The polymers were found to be soluble in DMF, DMSO, NMP, DMAc, and THF. All the polymers underwent two-stage decomposition and were stable up to 220 o C. Functionalized end-capping of poly(aryl-urea) using phenylchloroformate changed the thermal properties and solubility of the polymers. Copolymerization of AB2- type Blocked isocyante monomer with functionally similar AB monomer was also carried out. The molecular weights of copolymers were found to be higher than homopolymers with narrow dispersity. It was found that the Tg's of poly(aryl-urea)s were significantly less compared to copoly(aryl-urea).
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novel hyperbranched poly aryl ether urethane s using ab2 type Blocked Isocyanate monomers and copolymerization with ab type monomers
Macromolecular Chemistry and Physics, 2008Co-Authors: Thiyagarajan Shanmugam, Sultan A NasarAbstract:A novel AB 2 -type Blocked Isocyanate monomer was synthesized which was de-Blocked to provide a hyperbranched poly(aryl ether urethane). Copolymerization of this monomer with a functionally similar AB monomer yielded polymers with molecular weights in the range 8.0-310 kDa with a DB of 41-59% that underwent two-stage decomposition above 200 °C. The inherent viscosities of the polymers in DMF ranged from 0.09 to 1.10 dL g -1 . End-group modification of hyperbranched poly(aryl ether urethane)s was carried out with PEG monomethyl ether and 1-decanol and affected the thermal properties and solubilities of the polymers. T g of the polymers was reduced significantly from 201 to 71°C upon incorporation of AB monomer in the copolymerization.
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synthesis of poly urethane imide effect of solvents with and without basic nitrogen atom and other parameters on the imide formation reaction between Blocked Isocyanate prepolymers and pyromellitic dianhydride
Journal of Macromolecular Science Part A, 2005Co-Authors: Sultan A Nasar, A. Raghavan, Siva V KumarAbstract:N‐Methylaniline‐ and 2‐Butanone oxime‐Blocked Isocyanate prepolymers were prepared and their reaction with pyromellitic dianhydride (PMDA) was studied with a view to understand the effect of different parameters like solvents, temperature, blocking agents and deblocking catalysts [diazabicyclo 2.2.2 octane, (DABCO) and dibutyltin dilaurate, (DBTDL)] on the poly(urethane‐imide) formation reaction. The reactions were followed by the carbon dioxide evolved during the imidization reaction. The effect of each individual parameter was studied with the reaction time and GPC data. It was found that the reactions proceeded at a faster rate in hexamethyl phosphoric acid triamide (HMPA), a solvent having basic nitrogens, than in mesitylene. Also, in HMPA, it was found that the molecular weights (Mw) of the polymers increased with an increase in temperature up to 125°C and then decreased, whereas in mesitylene, it was found that there was no appreciable change in molecular weight up to 150°C. Of the two Blocked isocy...
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synthesis and properties of imidazole Blocked diIsocyanates
Polymer International, 1999Co-Authors: Sultan A Nasar, Sankaraiah Subramani, Ganga RadhakrishnanAbstract:Imidazole-, 2-methylimidazole- and benzimidazole-Blocked hexamethylene diIsocyanate and isophorone diIsocyanate have been prepared and characterized by elemental analyses, IR and NMR spectroscopy. The structure–property relationship of these adducts has been established by reacting with hydroxyl-terminated polybutadiene (HTPB). The cure rate of the adduct increases from the imidazole to 2-methylimidazole and to the benzimidazole-Blocked adduct. Also, the cure rate of the adducts based on hexamethylene diIsocyanate is higher than those based on isophorone diIsocyanate. Simultaneous TGA/DTA results also confirm this trend. The gas chromatogram of the imidazole-Blocked Isocyanate confirms that the thermolysis products are blocking agent and Isocyanate. The solubilities of the adducts have been measured in polyether and hydrocarbon polyols: the 2-methylimidazole and benzimidazole-Blocked hexamethylene diIsocyanate adducts show higher solubility than the rest. © 1999 Society of Chemical Industry
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the thermal dissociation of phenol Blocked toluene diIsocyanate crosslinkers
Polymer, 1993Co-Authors: H. Kothandaraman, Sultan A NasarAbstract:Abstract Several toluene diIsocyanates Blocked with various substituted phenols were prepared. They were characterized by elemental analysis, infra-red and 1 H nuclear magnetic resonance spectroscopy. The deblocking temperatures were determined by use of infra-red spectroscopy and by carbon dioxide evolution methods. The thermal stability of the Blocked Isocyanate was less for the ortho -substituted phenols than for the para isomers. Dissociation temperatures were also reduced by electron-withdrawing groups. The dissolution temperatures of the adducts were determined in propylene glycol, poly(ethylene glycol) 400 and hydroxyl-terminated poly(butadiene).
Zhengfa Zhou - One of the best experts on this subject based on the ideXlab platform.
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Blocked Isocyanate silane modified al2o3 polyamide 6 thermally conductive and electrical insulation composites with outstanding mechanical properties
RSC Advances, 2017Co-Authors: Fengmei Ren, Fang Sun, Ran Zhou, Zhengfa ZhouAbstract:The surface of alumina (Al2O3) particles was modified by a Blocked Isocyanate silane coupling agent, which was synthesized by using methylethyl ketoxime (MEKO) to block Isocyanate-propyltriethoxy silane via nucleophilic reactions. For comparison, the surface of Al2O3 particles was also modified by propyltrimethoxy silane (KH-331). The thermally conductive and electrical insulating Al2O3/polyamide 6 composites were prepared by dispersing modified Al2O3 in polyamide 6 (PA6) using a twin-screw extruder. The X-ray photoelectron spectroscopy (XPS) results revealed that Blocked Isocyanate-propyltriethoxy silane and KH-331 were successfully attached to the surface of Al2O3 particles with chemical bonds. The Blocked Isocyanate silane modified Al2O3 were well dispersed in PA6 as revealed by scanning electron microscopy (SEM). When the Al2O3 content was 70 wt%, the tensile strength (85.2 MPa) and flexural strength (136.4 MPa) of Blocked Isocyanate silane modified Al2O3/PA6 composites were higher than those of KH-331 modified Al2O3/PA6 composites (52.5 MPa, 77.8 MPa), respectively. The thermal conductivity and impact strength of Blocked Isocyanate silane modified Al2O3/PA6 composites were also higher than that of KH-331 modified Al2O3/PA6 composites at the same content of Al2O3. The volume electrical resistivity of modified Al2O3/PA6 composites decreased with increasing Al2O3 content, but they still were good electrical insulating materials.
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Blocked Isocyanate silane modified Al2O3/polyamide 6 thermally conductive and electrical insulation composites with outstanding mechanical properties
RSC Advances, 2017Co-Authors: Fengmei Ren, Zhou Ran, Fang Sun, Ma Haihong, Zhengfa ZhouAbstract:The surface of alumina (Al2O3) particles was modified by a Blocked Isocyanate silane coupling agent, which was synthesized by using methylethyl ketoxime (MEKO) to block Isocyanate-propyltriethoxy silane via nucleophilic reactions. For comparison, the surface of Al2O3 particles was also modified by propyltrimethoxy silane (KH-331). The thermally conductive and electrical insulating Al2O3/polyamide 6 composites were prepared by dispersing modified Al2O3 in polyamide 6 (PA6) using a twin-screw extruder. The X-ray photoelectron spectroscopy (XPS) results revealed that Blocked Isocyanate-propyltriethoxy silane and KH-331 were successfully attached to the surface of Al2O3 particles with chemical bonds. The Blocked Isocyanate silane modified Al2O3 were well dispersed in PA6 as revealed by scanning electron microscopy (SEM). When the Al2O3 content was 70 wt%, the tensile strength (85.2 MPa) and flexural strength (136.4 MPa) of Blocked Isocyanate silane modified Al2O3/PA6 composites were higher than those of KH-331 modified Al2O3/PA6 composites (52.5 MPa, 77.8 MPa), respectively. The thermal conductivity and impact strength of Blocked Isocyanate silane modified Al2O3/PA6 composites were also higher than that of KH-331 modified Al2O3/PA6 composites at the same content of Al2O3. The volume electrical resistivity of modified Al2O3/PA6 composites decreased with increasing Al2O3 content, but they still were good electrical insulating materials.
Fengmei Ren - One of the best experts on this subject based on the ideXlab platform.
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Blocked Isocyanate silane modified al2o3 polyamide 6 thermally conductive and electrical insulation composites with outstanding mechanical properties
RSC Advances, 2017Co-Authors: Fengmei Ren, Fang Sun, Ran Zhou, Zhengfa ZhouAbstract:The surface of alumina (Al2O3) particles was modified by a Blocked Isocyanate silane coupling agent, which was synthesized by using methylethyl ketoxime (MEKO) to block Isocyanate-propyltriethoxy silane via nucleophilic reactions. For comparison, the surface of Al2O3 particles was also modified by propyltrimethoxy silane (KH-331). The thermally conductive and electrical insulating Al2O3/polyamide 6 composites were prepared by dispersing modified Al2O3 in polyamide 6 (PA6) using a twin-screw extruder. The X-ray photoelectron spectroscopy (XPS) results revealed that Blocked Isocyanate-propyltriethoxy silane and KH-331 were successfully attached to the surface of Al2O3 particles with chemical bonds. The Blocked Isocyanate silane modified Al2O3 were well dispersed in PA6 as revealed by scanning electron microscopy (SEM). When the Al2O3 content was 70 wt%, the tensile strength (85.2 MPa) and flexural strength (136.4 MPa) of Blocked Isocyanate silane modified Al2O3/PA6 composites were higher than those of KH-331 modified Al2O3/PA6 composites (52.5 MPa, 77.8 MPa), respectively. The thermal conductivity and impact strength of Blocked Isocyanate silane modified Al2O3/PA6 composites were also higher than that of KH-331 modified Al2O3/PA6 composites at the same content of Al2O3. The volume electrical resistivity of modified Al2O3/PA6 composites decreased with increasing Al2O3 content, but they still were good electrical insulating materials.
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Blocked Isocyanate silane modified Al2O3/polyamide 6 thermally conductive and electrical insulation composites with outstanding mechanical properties
RSC Advances, 2017Co-Authors: Fengmei Ren, Zhou Ran, Fang Sun, Ma Haihong, Zhengfa ZhouAbstract:The surface of alumina (Al2O3) particles was modified by a Blocked Isocyanate silane coupling agent, which was synthesized by using methylethyl ketoxime (MEKO) to block Isocyanate-propyltriethoxy silane via nucleophilic reactions. For comparison, the surface of Al2O3 particles was also modified by propyltrimethoxy silane (KH-331). The thermally conductive and electrical insulating Al2O3/polyamide 6 composites were prepared by dispersing modified Al2O3 in polyamide 6 (PA6) using a twin-screw extruder. The X-ray photoelectron spectroscopy (XPS) results revealed that Blocked Isocyanate-propyltriethoxy silane and KH-331 were successfully attached to the surface of Al2O3 particles with chemical bonds. The Blocked Isocyanate silane modified Al2O3 were well dispersed in PA6 as revealed by scanning electron microscopy (SEM). When the Al2O3 content was 70 wt%, the tensile strength (85.2 MPa) and flexural strength (136.4 MPa) of Blocked Isocyanate silane modified Al2O3/PA6 composites were higher than those of KH-331 modified Al2O3/PA6 composites (52.5 MPa, 77.8 MPa), respectively. The thermal conductivity and impact strength of Blocked Isocyanate silane modified Al2O3/PA6 composites were also higher than that of KH-331 modified Al2O3/PA6 composites at the same content of Al2O3. The volume electrical resistivity of modified Al2O3/PA6 composites decreased with increasing Al2O3 content, but they still were good electrical insulating materials.
A. Sultan Nasar - One of the best experts on this subject based on the ideXlab platform.
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Amine- and Blocked Isocyanate-terminated polyurethane dendrimers: integrated synthesis, photophysical properties and application in a heat curable system
RSC Advances, 2015Co-Authors: S. Veerapandian, A. Sultan NasarAbstract:A highly efficient, scalable, three step divergent synthesis of Blocked Isocyanate-terminated polyurethane dendrimers up to fourth generation (G4) has been developed avoiding the formation of free Isocyanate. Amine-terminated polyurethane dendrimers were obtained as complementary functional materials in the second step. The Blocked Isocyanate moiety possessing easily cleavable blocking agents facilitated the dendrimer construction. Heat-curable adhesives based on G2 dendrimers tested on aluminum plates showed tensile shear strength of 2.41 MPa.
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Novel Hyperbranched Poly(aryl ether urethane)s Using AB2‐Type Blocked Isocyanate Monomers and Copolymerization with AB‐Type Monomers
Macromolecular Chemistry and Physics, 2008Co-Authors: Thiyagarajan Shanmugam, A. Sultan NasarAbstract:A novel AB 2 -type Blocked Isocyanate monomer was synthesized which was de-Blocked to provide a hyperbranched poly(aryl ether urethane). Copolymerization of this monomer with a functionally similar AB monomer yielded polymers with molecular weights in the range 8.0-310 kDa with a DB of 41-59% that underwent two-stage decomposition above 200 °C. The inherent viscosities of the polymers in DMF ranged from 0.09 to 1.10 dL g -1 . End-group modification of hyperbranched poly(aryl ether urethane)s was carried out with PEG monomethyl ether and 1-decanol and affected the thermal properties and solubilities of the polymers. T g of the polymers was reduced significantly from 201 to 71°C upon incorporation of AB monomer in the copolymerization.
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Synthesis and properties of hyperbranched polyurethanes, hyperbranched polyurethane copolymers with and without ether and ester groups using Blocked Isocyanate monomers
Journal of Polymer Science Part A: Polymer Chemistry, 2007Co-Authors: Mahalingam Vanjinathan, A. Shanavas, A. Raghavan, A. Sultan NasarAbstract:Starting from 3,5-diamino benzoic acid, 2-hydroxy propyl[3,5-bis{(benzoxycarbonyl)imino}]benzyl ether, an AB2-type Blocked Isocyanate monomer with flexible ether group, and 2-hydroxy propyl[3,5-bis{(benzoxycarbonyl)imino}]benzoate, an AB2-type Blocked Isocyanate monomer with ester group, were synthesized for the first time. Using the same starting compound, 3,5-bis{(benzoxycarbonyl)imino}benzylalcohol, an AB2-type Blocked Isocyanate monomer, was synthesized through a highly efficient short-cut route. Step-growth polymerization of these monomers at individually optimized experimental conditions results in the formation of hyperbranched polyurethanes with and without ether and ester groups. Copolymerizations of these monomers with functionally similar AB monomers were also carried out. The molecular weights of the polymers were determined using GPC and the values (Mw) were found to vary from 1.5 × 104 to 1.2 × 106. While hyperbranched polyurethanes having no ether or ester group were found to be thermally stable up to 217 °C, hyperbranched poly(ether–urethane)s and poly(ester–urethane)s were found to be thermally stable up to 245 and 300 °C, respectively. Glass transition temperature (Tg) of polyurethane was reduced significantly when introducing ether groups into the polymer chain, whereas Tg was not observed even up to 250 °C in the case of poly(ester–urethane). Hyperbranched polyurethanes derived from all the three different AB2 monomers were soluble in highly polar solvents and the copolymers showed improved solubility. Polyethylene glycol monomethyl ether of molecular weight 550 and decanol were used as end-capping groups, which were seen to affect the thermal, solution, and solubility properties of polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3877–3893, 2007
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Hyperbranched poly(ether-urea)s using AB2-type Blocked Isocyanate monomer and azide monomer: Synthesis, characterization, reactive end functionalization, and copolymerization with AB monomer
Journal of Polymer Science Part A: Polymer Chemistry, 2007Co-Authors: Mahalingam Vanjinathan, A. Raghavan, A. Sultan NasarAbstract:3,5-bis(4-aminophenoxy)phenyl phenylcarbamate-a novel AB 2 -type Blocked Isocyanate monomer and 3,5-bis(ethyleneoxy(4-aminophenoxy)lphenyl carbonyl azide-a novel AB 2 -type azide monomer were synthesized in high yield. Step-growth polymerization of these monomers were found to give a first example of hyperbranched poly (aryl-ether-urea) and poly(aryl-alkyl-ether-urea). Molecular weights (M W ) of the polymer were found to vary from 1,858 to 52,432 depending upon the monomer and experimental conditions used. The polydispersity indexes were relatively narrow due to the controlled regeneration of Isocyanate functional groups for the polymerization reaction. The degree of branching (DB) was determined using 1 H-NMR spectroscopy and the values ranged from 87 to 54%. All the polymers underwent two-stage decomposition and were stable up to 300 °C. Functionalized end-capping of poly(aryl-ether-urea) using phenylchloroformate and di-t-butyl dicarbonate (Boc) 2 O changed the thermal properties and solubility of the polymers. Copolymerization of AB 2 -type Blocked isocyante monomer with functionally similar AB monomer were also carried out. The molecular weights of copolymers were found to be in the order of 6 X 10 5 with narrow dispersity. It was found that the Tg's of poly(aryl-alkyl-ether-urea)s were significantly less (46-49 °C) compared to poly(aryl-ether-urea)s. Moreover the former showed melting transition at 154 °C, which was not observed in the latter case.
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Synthesis of Poly(Urethane‐Imide): Effect of Solvents with and without Basic Nitrogen Atom and Other Parameters on the Imide Formation Reaction Between Blocked‐Isocyanate Prepolymers and Pyromellitic Dianhydride
Journal of Macromolecular Science Part A, 2005Co-Authors: A. Sultan Nasar, A. Raghavan, V. Siva KumarAbstract:N‐Methylaniline‐ and 2‐Butanone oxime‐Blocked Isocyanate prepolymers were prepared and their reaction with pyromellitic dianhydride (PMDA) was studied with a view to understand the effect of different parameters like solvents, temperature, blocking agents and deblocking catalysts [diazabicyclo 2.2.2 octane, (DABCO) and dibutyltin dilaurate, (DBTDL)] on the poly(urethane‐imide) formation reaction. The reactions were followed by the carbon dioxide evolved during the imidization reaction. The effect of each individual parameter was studied with the reaction time and GPC data. It was found that the reactions proceeded at a faster rate in hexamethyl phosphoric acid triamide (HMPA), a solvent having basic nitrogens, than in mesitylene. Also, in HMPA, it was found that the molecular weights (Mw) of the polymers increased with an increase in temperature up to 125°C and then decreased, whereas in mesitylene, it was found that there was no appreciable change in molecular weight up to 150°C. Of the two Blocked isocy...
Fang Sun - One of the best experts on this subject based on the ideXlab platform.
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Blocked Isocyanate silane modified al2o3 polyamide 6 thermally conductive and electrical insulation composites with outstanding mechanical properties
RSC Advances, 2017Co-Authors: Fengmei Ren, Fang Sun, Ran Zhou, Zhengfa ZhouAbstract:The surface of alumina (Al2O3) particles was modified by a Blocked Isocyanate silane coupling agent, which was synthesized by using methylethyl ketoxime (MEKO) to block Isocyanate-propyltriethoxy silane via nucleophilic reactions. For comparison, the surface of Al2O3 particles was also modified by propyltrimethoxy silane (KH-331). The thermally conductive and electrical insulating Al2O3/polyamide 6 composites were prepared by dispersing modified Al2O3 in polyamide 6 (PA6) using a twin-screw extruder. The X-ray photoelectron spectroscopy (XPS) results revealed that Blocked Isocyanate-propyltriethoxy silane and KH-331 were successfully attached to the surface of Al2O3 particles with chemical bonds. The Blocked Isocyanate silane modified Al2O3 were well dispersed in PA6 as revealed by scanning electron microscopy (SEM). When the Al2O3 content was 70 wt%, the tensile strength (85.2 MPa) and flexural strength (136.4 MPa) of Blocked Isocyanate silane modified Al2O3/PA6 composites were higher than those of KH-331 modified Al2O3/PA6 composites (52.5 MPa, 77.8 MPa), respectively. The thermal conductivity and impact strength of Blocked Isocyanate silane modified Al2O3/PA6 composites were also higher than that of KH-331 modified Al2O3/PA6 composites at the same content of Al2O3. The volume electrical resistivity of modified Al2O3/PA6 composites decreased with increasing Al2O3 content, but they still were good electrical insulating materials.
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Blocked Isocyanate silane modified Al2O3/polyamide 6 thermally conductive and electrical insulation composites with outstanding mechanical properties
RSC Advances, 2017Co-Authors: Fengmei Ren, Zhou Ran, Fang Sun, Ma Haihong, Zhengfa ZhouAbstract:The surface of alumina (Al2O3) particles was modified by a Blocked Isocyanate silane coupling agent, which was synthesized by using methylethyl ketoxime (MEKO) to block Isocyanate-propyltriethoxy silane via nucleophilic reactions. For comparison, the surface of Al2O3 particles was also modified by propyltrimethoxy silane (KH-331). The thermally conductive and electrical insulating Al2O3/polyamide 6 composites were prepared by dispersing modified Al2O3 in polyamide 6 (PA6) using a twin-screw extruder. The X-ray photoelectron spectroscopy (XPS) results revealed that Blocked Isocyanate-propyltriethoxy silane and KH-331 were successfully attached to the surface of Al2O3 particles with chemical bonds. The Blocked Isocyanate silane modified Al2O3 were well dispersed in PA6 as revealed by scanning electron microscopy (SEM). When the Al2O3 content was 70 wt%, the tensile strength (85.2 MPa) and flexural strength (136.4 MPa) of Blocked Isocyanate silane modified Al2O3/PA6 composites were higher than those of KH-331 modified Al2O3/PA6 composites (52.5 MPa, 77.8 MPa), respectively. The thermal conductivity and impact strength of Blocked Isocyanate silane modified Al2O3/PA6 composites were also higher than that of KH-331 modified Al2O3/PA6 composites at the same content of Al2O3. The volume electrical resistivity of modified Al2O3/PA6 composites decreased with increasing Al2O3 content, but they still were good electrical insulating materials.