The Experts below are selected from a list of 34464 Experts worldwide ranked by ideXlab platform
Alain Dufresne - One of the best experts on this subject based on the ideXlab platform.
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crab shell chitin whisker reinforced natural rubber nanocomposites 1 processing and swelling behavior
Biomacromolecules, 2003Co-Authors: Kalaprasad Gopalan Nair, Alain DufresneAbstract:Nanocomposite materials were obtained from a colloidal suspension of chitin whiskers as the reinforcing phase and latex of both unvulcanized and prevulcanized natural rubber as the matrix. The chitin whiskers, prepared by acid hydrolysis of chitin from crab shell, consisted of slender parallelepiped rods with an aspect ratio close to 16. After the two aqueous suspensions were mixed and strirred, solid composite films were obtained either by freeze-drying and hot-pressing or by casting and evaporating the preparations. The processing and swelling behavior of composite films were evaluated. It was concluded that the whiskers form a rigid network assumed to be governed by a percolation mechanism in the evaporated samples only. Comparatively, better resistance of evaporated samples than hot-pressed ones against swelling in an organic Solvent Medium is good evidence for the existence of a rigid chitin network. The values of diffusion coefficient, bound rubber content, and relative weight loss also supported th...
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crab shell chitin whisker reinforced natural rubber nanocomposites 1 processing and swelling behavior
Biomacromolecules, 2003Co-Authors: Kalaprasad Gopalan Nair, Alain DufresneAbstract:Nanocomposite materials were obtained from a colloidal suspension of chitin whiskers as the reinforcing phase and latex of both unvulcanized and prevulcanized natural rubber as the matrix. The chitin whiskers, prepared by acid hydrolysis of chitin from crab shell, consisted of slender parallelepiped rods with an aspect ratio close to 16. After the two aqueous suspensions were mixed and strirred, solid composite films were obtained either by freeze-drying and hot-pressing or by casting and evaporating the preparations. The processing and swelling behavior of composite films were evaluated. It was concluded that the whiskers form a rigid network assumed to be governed by a percolation mechanism in the evaporated samples only. Comparatively, better resistance of evaporated samples than hot-pressed ones against swelling in an organic Solvent Medium is good evidence for the existence of a rigid chitin network. The values of diffusion coefficient, bound rubber content, and relative weight loss also supported the presence of a three-dimensional chitin network within the evaporated samples. The mechanical behavior of the composites gives additional insight and evidence for this fact (part 2).
Kalaprasad Gopalan Nair - One of the best experts on this subject based on the ideXlab platform.
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crab shell chitin whisker reinforced natural rubber nanocomposites 1 processing and swelling behavior
Biomacromolecules, 2003Co-Authors: Kalaprasad Gopalan Nair, Alain DufresneAbstract:Nanocomposite materials were obtained from a colloidal suspension of chitin whiskers as the reinforcing phase and latex of both unvulcanized and prevulcanized natural rubber as the matrix. The chitin whiskers, prepared by acid hydrolysis of chitin from crab shell, consisted of slender parallelepiped rods with an aspect ratio close to 16. After the two aqueous suspensions were mixed and strirred, solid composite films were obtained either by freeze-drying and hot-pressing or by casting and evaporating the preparations. The processing and swelling behavior of composite films were evaluated. It was concluded that the whiskers form a rigid network assumed to be governed by a percolation mechanism in the evaporated samples only. Comparatively, better resistance of evaporated samples than hot-pressed ones against swelling in an organic Solvent Medium is good evidence for the existence of a rigid chitin network. The values of diffusion coefficient, bound rubber content, and relative weight loss also supported th...
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crab shell chitin whisker reinforced natural rubber nanocomposites 1 processing and swelling behavior
Biomacromolecules, 2003Co-Authors: Kalaprasad Gopalan Nair, Alain DufresneAbstract:Nanocomposite materials were obtained from a colloidal suspension of chitin whiskers as the reinforcing phase and latex of both unvulcanized and prevulcanized natural rubber as the matrix. The chitin whiskers, prepared by acid hydrolysis of chitin from crab shell, consisted of slender parallelepiped rods with an aspect ratio close to 16. After the two aqueous suspensions were mixed and strirred, solid composite films were obtained either by freeze-drying and hot-pressing or by casting and evaporating the preparations. The processing and swelling behavior of composite films were evaluated. It was concluded that the whiskers form a rigid network assumed to be governed by a percolation mechanism in the evaporated samples only. Comparatively, better resistance of evaporated samples than hot-pressed ones against swelling in an organic Solvent Medium is good evidence for the existence of a rigid chitin network. The values of diffusion coefficient, bound rubber content, and relative weight loss also supported the presence of a three-dimensional chitin network within the evaporated samples. The mechanical behavior of the composites gives additional insight and evidence for this fact (part 2).
Marcio W Paixao - One of the best experts on this subject based on the ideXlab platform.
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polyethylene glycol peg as a reusable Solvent Medium for an asymmetric organocatalytic michael addition application to the synthesis of bioactive compounds
ChemInform, 2014Co-Authors: Karla S Feu, Alexander F De La Torre, Sandrina Silva, Marco A F De Moraes, Arlene G Correa, Marcio W PaixaoAbstract:A highly stereoselective organocatalytic Michael addition of aldehydes to trans-β-styrenes (I) using polyethylene glycol as a recyclable Solvent Medium is reported.
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polyethylene glycol peg as a reusable Solvent Medium for an asymmetric organocatalytic michael addition application to the synthesis of bioactive compounds
Green Chemistry, 2014Co-Authors: Karla S Feu, Alexander F De La Torre, Sandrina Silva, Marco A F De Moraes, Arlene G Correa, Marcio W PaixaoAbstract:A highly stereoselective organocatalytic Michael addition of aldehydes to trans-β-nitrostyrenes using PEG as a recyclable Solvent Medium is presented. The scope of this organocatalytic system is demonstrated by the formation of several Michael adducts in good yields and stereoselectivities. Furthermore, applying this new protocol to acetaldehyde, we have disclosed an easy formal synthesis of (R)-pregabalin, (R)-phenibut and (R)-bacoflen with good yields and outstanding enantioselectivities.
Tulasi Prasad Niraula - One of the best experts on this subject based on the ideXlab platform.
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Effects of concentration, temperature and Solvent composition on density and apparent molar volume of the binary mixtures of cationic-anionic surfactants in methanol–water mixed Solvent media
SpringerPlus, 2013Co-Authors: Ajaya Bhattarai, Sujeet Kumar Chatterjee, Tulasi Prasad NiraulaAbstract:The accurate measurements on density of the binary mixtures of cetyltrimethylammonium bromide and sodium dodecyl sulphate in pure water and in methanol(1) + water (2) mixed Solvent media containing (0.10, 0.20, and 0.30) volume fractions of methanol at 308.15, 318.15, and 323.15 K are reported. The concentrations are varied from (0.03 to 0.12) mol.l^-1 of sodium dodecyl sulphate in presence of ~ 5.0×10^-4 mol.l^-1 cetyltrimethylammonium bromide. The results showed almost increase in the densities with increasing surfactant mixture concentration, also the densities are found to decrease with increasing temperature over the entire concentration range, investigated in a given mixed Solvent Medium and these values are found to decrease with increasing methanol content in the Solvent composition. The concentration dependence of the apparent molar volumes appear to be negligible over the entire concentration range, investigated in a given mixed Solvent Medium and the apparent molar volumes increase with increasing temperature and are found to decrease with increasing methanol content in the Solvent composition.
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effects of concentration temperature and Solvent composition on the partial molar volumes of sodium lauryl sulfate in methanol 1 water 2 mixed Solvent media
Journal of Chemical & Engineering Data, 2011Co-Authors: Ajaya Bhattarai, Sujeet Kumar Chatterjee, Tarun K Deo, Tulasi Prasad NiraulaAbstract:Precise measurements on the density of sodium lauryl sulfate in pure water and in methanol (1) + water (2) mixed Solvent media containing (0.10, 0.20, 0.30, and 0.40) volume fractions of methanol at (298.15, 308.15, 318.15, and 323.15) K are reported. The concentrations are varied from (0.3·10–1 to 1.3·10–1) mol·kg–1. The results were almost constant on the partial molar volumes with increasing surfactant concentration. Also, the partial molar volumes are found to increase with increasing temperature over the entire concentration range investigated in a given mixed Solvent Medium and are found to decrease with increasing methanol content in the Solvent composition.
S Chandrasekhar - One of the best experts on this subject based on the ideXlab platform.
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copper catalyzed n arylation of amines amides in poly ethylene glycol as recyclable Solvent Medium
ChemInform, 2006Co-Authors: S Chandrasekhar, Shameem S Sultana, Srinivasarao Yaragorla, Ramakrishna N ReddyAbstract:The Buchwald N-arylation of amines and amides is achieved efficiently in PEG (400 Daltons) as Solvent Medium. The Solvent and catalyst recyclability is studied. Interestingly amides underwent N-arylation with better yields.
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poly ethylene glycol 400 as superior Solvent Medium against ionic liquids for catalytic hydrogenations with pto2
Journal of Organic Chemistry, 2006Co-Authors: S Chandrasekhar, Samala Jaya Prakash, Chennamaneni Lohitha RaoAbstract:Adams' catalyst in poly(ethylene glycol) (PEG) (400) has been found to be a superior Solvent over the ionic liquids by severalfold in promoting the hydrogenation of various functional groups. Both the catalyst and PEG were recycled efficiently over 10 runs without loss of activity, and substrate cross contamination was not observed despite a change in the substrate four times.
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poly ethylene glycol peg as a reusable Solvent Medium for organic synthesis application in the heck reaction
Organic Letters, 2002Co-Authors: S Chandrasekhar, Ch Narsihmulu, Shameem S Sultana, Ramakrishna N ReddyAbstract:PEG has been used as a Solvent Medium for regioselective Heck reactions with easy recyclability of Solvent and Pd catalyst for the first time.