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Jin-San Kim Tara Sankar Pathak Jung-Ho Yun Ki-Pal Kim Tae-Joon Park Yongae Kim Ki-Jung Paeng 《Journal of Polymers and the Environment》2013,21(1):224-232
Alginate polyurethane hybrid materials are prepared by varying mole ratio of 2, 4-TDI as a di-isocyanate and alginic acid as a polyol in presence of dimethyl sulfoxide (DMSO) as a solvent. FT-IR and 13C one-dimensional (1D) solid state NMR (SSNMR) spectroscopy indicates that alginic acid is converted into alginate-polyurethane hybrid material via urethane linkage. Surface morphology of alginate-polyurethane hybrids changes by varying alginic acid: TDI ratio. The peak at near 221 °C in DSC thermogram of alginic acid (Alg) is shifted to higher temperature in alginate-polyurethane hybrid (Algpu1 and Algpu2). TGA study shows that alginate-polyurethane hybrid prepared using alginic acid: TDI = 1:1 (Algpu2) is more stable than alginic acid: TDI = 1:0.5 (Algpu1) at 300 °C. Kinetic analysis was performed to fit with TGA data, where the entire degradation process has been considered as three consecutive 1st order reactions. This study shows that thermal stability of alginate-polyurethane hybrid material was increased by adjusting mole ratio of 2, 4-TDI and alginic acid. 相似文献
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Tara Sankar Pathak Jin San Kim Se-Jong Lee Dae-Jin Baek Ki-Jung Paeng 《Journal of Polymers and the Environment》2008,16(3):198-204
Alginic acid and metal alginates are prepared from fresh algae using extraction method. A FTIR spectrum indicates that alginic
acid is converted into the metal alginate. Comparing calcium and cobalt alginates, asymmetric stretching of free carboxyl
group of calcium alginate at 1630 cm−1 is shifted to 1585 cm−1 in cobalt alginate, due to the change of charge density, radius and atomic weight of the cation, creating a new environment
around the carbonyl group. The strong exothermic peak of alginic acid in DSC thermogram indicates the decomposition of biopolymer,
whereas strong exothermic peak of metal alginate in DSC thermogram attributed to the decomposition of biopolymer and formation
of respective carbonate. Based on DSC study, the decomposition of cobalt alginate occurs at higher temperature comparing to
those of sodium and calcium alginate, which may conclude into the higher stability of cobalt alginate. TGA results reveal
that, cobalt alginate is more stable than calcium and sodium alginate at 300 °C temperature. Surface morphology (at same magnification),
as well as porosity (%) and pore size distribution results change with metals present in different metal alginates. 相似文献
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Tara Sankar Pathak Jung-Ho Yun Se-Jong Lee Dae-Jin Baek Ki-Jung Paeng 《Journal of Polymers and the Environment》2010,18(1):45-56
Alginates, extracted from algae are linear unbranched polymers containing β-(1→4)-linked d-mannuronic acid (M) and α-(1→4)-linked l-guluronic acid (G) residues. The conversion of alginic acid into the metal alginate is confirmed using FTIR spectroscopy.
Asymmetric and symmetric stretching of free carboxyl group present in metal alginate occurs almost at the same position in
various solvent compositions. Total intrusion volume of metal alginate prepared in propanol (0.0742 mL/g) is greater compared
to those in ethanol (0.0648 mL/g) and methanol (0.0393 mL/g) as solvent. Surface morphology as well as porosity and pore size
distribution of metal alginate are greatly influenced by solvent. It can be seen from thermal analysis results that calcium
alginate prepared using different solvent compositions started decomposing at 100 °C, but rapid degradation started around
200 °C. The results showed a stepwise weight loss during thermal sweep, indicating different types of reactions during degradation.
First and second step of rapid degradation was situated around 200–300 and 300–550 °C, respectively; whereas the final step
is situated around 550–650 °C. The trend of degradation was similar for all the solvents, although the amount of final residue
varied from one solvent to another. At the same time, lower thermal stability was also observed with higher heating rates.
Additionally, a kinetic analysis was performed to fit with TGA data, where the entire degradation process has been considered
as three consecutive first order reactions. 相似文献
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