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Sungseen Choi - One of the best experts on this subject based on the ideXlab platform.
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novel analytical method for determination of contents of backbone and terminal branch vinyl acetate groups of poly ethylene co vinyl acetate using Deacetylation reaction
Polymer Testing, 2016Co-Authors: Sungseen ChoiAbstract:Abstract Vinyl acetate (VA) groups in poly(ethylene-co-vinyl acetate) (EVA) exist in backbone, terminal, and branch positions. The VA moieties were converted to carbon-carbon double bonds (∼CH=CH∼) by Deacetylation reaction. By Deacetylation, the backbone VA group was converted to 1,4-unit (∼CH2CH=CHCH2∼) while the terminal and branch ones were converted to 1,2-unit (∼CH=CH2). A novel analytical method for determination of ratio of backbone and terminal/branch VA contents was developed using off-line pyrolysis and transmission-Fourier transform infrared spectroscopy (FTIR). The analytical method included sample preparation of deacetylated EVA coated on NaCl window for transmission-FTIR analysis and calculation of backbone and terminal/branch VA contents using quantitative analysis of 1,4- and 1,2-units of the deacetylated EVA. Influence of Deacetylation conditions (pyrolysis temperatures and times) on degree of Deacetylation and other side reactions was also investigated, and proper Deacetylation condition was suggested. From the experimental results, proper off-line pyrolysis condition of EVA coated on NaCl window was 300 °C for 60–80 min. The novel analytical method was reliable with the experimental error of below 5%.
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Novel analytical method for determination of contents of backbone and terminal/branch vinyl acetate groups of poly(ethylene-co-vinyl acetate) using Deacetylation reaction
Polymer Testing, 2016Co-Authors: Sungseen ChoiAbstract:Abstract Vinyl acetate (VA) groups in poly(ethylene-co-vinyl acetate) (EVA) exist in backbone, terminal, and branch positions. The VA moieties were converted to carbon-carbon double bonds (∼CH=CH∼) by Deacetylation reaction. By Deacetylation, the backbone VA group was converted to 1,4-unit (∼CH2CH=CHCH2∼) while the terminal and branch ones were converted to 1,2-unit (∼CH=CH2). A novel analytical method for determination of ratio of backbone and terminal/branch VA contents was developed using off-line pyrolysis and transmission-Fourier transform infrared spectroscopy (FTIR). The analytical method included sample preparation of deacetylated EVA coated on NaCl window for transmission-FTIR analysis and calculation of backbone and terminal/branch VA contents using quantitative analysis of 1,4- and 1,2-units of the deacetylated EVA. Influence of Deacetylation conditions (pyrolysis temperatures and times) on degree of Deacetylation and other side reactions was also investigated, and proper Deacetylation condition was suggested. From the experimental results, proper off-line pyrolysis condition of EVA coated on NaCl window was 300 °C for 60–80 min. The novel analytical method was reliable with the experimental error of below 5%.
Luiz Antonio De Almeida Pinto - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of molar weight and Deacetylation degree of chitosan during chitin Deacetylation reaction: Used to produce biofilm
Chemical Engineering and Processing: Process Intensification, 2011Co-Authors: Catarina Motta De Moura, Jaqueline Motta De Moura, Niege Madeira Soares, Luiz Antonio De Almeida PintoAbstract:Abstract Chitosan is a polysaccharide derived from chitin, mainly of crustacean shells and shrimp wastes. The utilization of chitosan is related to the molar weight and Deacetylation degree of the biopolymer. The aim of this work is to study the chitin Deacetylation reaction, by the viscosity average molar weight and Deacetylation degree of chitosan as a function of reaction time. Deacetylation was carried out in concentrated alkaline solution, 421 g L −1 , at 130 °C and the reaction occurred during 4 h. Chitosan paste obtained after 20, 90 and 240 min was used to produce biofilms, which were characterized according water vapor permeability and mechanical properties (tensile strength and percentage tensile elongation at break). During the reaction time Deacetylation degree reached 93%, and a 50% reduction in the viscosity average molar weight value in relation to the value of the first 20 min of reaction was found Both reactions presented a kinetic behavior of the pseudo-first order. Biofilm produced from the paste of chitosan with high Deacetylation degree showed higher water vapor permeability (WVP), tensile strength (TS) and elongation ( E ) when compared to films with a low Deacetylation.
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optimization of Deacetylation in the production of chitosan from shrimp wastes use of response surface methodology
Journal of Food Engineering, 2007Co-Authors: Raquel Farias Weska, Jaqueline De Motta Moura, Lucia M Batista, Jaques Rizzi, Luiz Antonio De Almeida PintoAbstract:The use of chitosan in diverse areas is directly related to the polymer's molecular weight and degree of Deacetylation, which depends on the conditions of chitin Deacetylation. The aim of the present study consisted of optimization of the Deacetylation stage in the production of chitosan, using the response surface methodology for the polymer's molecular weight. Chitin was obtained from shrimp wastes and the study of Deacetylation made through a factorial experimental design, where temperature and time were varied. The estimate of chitosan's intrinsic viscosity was made by linear regression with the values of reduced viscosity and concentration, using Huggins equation for polymers. The viscosity average molecular weight of chitosan was calculated for each experiment by the equation by Mark-Houwink-Sakurada that relates the intrinsic viscosity to the polymer's molecular weight. The optimum condition for the Deacetylation reaction for molecular weight was observed at a temperature of 130 °C and in 90 min, and corresponded to a molecular weight of chitosan of about 150 kDa, and a Deacetylation degree of 90%.
Tatiana Volkova - One of the best experts on this subject based on the ideXlab platform.
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Effect of Heterogeneous Deacetylation on the Properties of Northern Shrimp Chitin and Chitosan
KnE Life Sciences, 2020Co-Authors: Nataliia Dolgopiatova, Yuliya A. Kuchina, Tatiana Dyakina, Tatiana VolkovaAbstract:The effect of alkaline treatment of shrimp chitin on the molecular weight, the degree of Deacetylation and degree of crystallinity of the resulting chitosan is studied. The viscosity of chitosan solutions from repeatedly deacetylated chitin is studied. It is shown that repeated treatment of chitin/chitosan with alkali causes the destruction of polysaccharide macromolecules. After four-time Deacetylation and one-time Deacetylation of chitin/chitosan for four hours, the molecular weight of the polysaccharide decreases by ten times. The maximum degree of chitosan Deacetylation under experimental conditions was 92.0 -92.5%. The diffractograms of chitin and chitosan from the Northern shrimp are of the form typical for samples containing an amorphous phase in addition to a crystalline phase. The degree of crystallinity of chitin from Northern shrimp was 40.8%, of chitosan samples after one-, two-, and three-time Deacetylation was 62-65%. For a sample of chitosan obtained after four-time Deacetylation, recrystallization, and drying in a freeze dryer, the degree of crystallinity is close to the degree of crystallinity of shrimp chitin. The investigated acetic acid chitosan solutions with a concentration of 5% (wt.) and the chitosan molecular weight of 250, 160 and 130 kDa in their rheological properties are liquid-like non-Newtonian systems, their viscosity decreasing with increasing shear stress. After four-time Deacetylation of chitin, the viscosity of chitosan solutions practically does not change with increasing shear stress, which apparently can be due to a significant decrease in the molecular weight of chitosan under these conditions.
Fugaku Aoki - One of the best experts on this subject based on the ideXlab platform.
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inadequate histone Deacetylation during oocyte meiosis causes aneuploidy and embryo death in mice
Proceedings of the National Academy of Sciences of the United States of America, 2006Co-Authors: Tomohiko Akiyama, Masao Nagata, Fugaku AokiAbstract:Errors in meiotic chromosome segregation are the leading cause of spontaneous abortions and birth defects. Almost all such aneuploidy derives from meiotic errors in females, with increasing maternal age representing a major risk factor. It was recently reported that histones are globally deacetylated in mammalian oocytes during meiosis but not mitosis. In the present study, inhibition of meiotic histone Deacetylation was found to induce aneuploidy in fertilized mouse oocytes, which resulted in embryonic death in utero at an early stage of development. In addition, a histone remained acetylated in the oocytes of older (10-month-old) female mice, suggesting that the function for histone Deacetylation is decreased in the oocytes of such mice. Thus, histone Deacetylation may be involved in the fair distribution of chromosomes during meiotic division. The high incidence of aneuploidy in the embryos of older females may be due to inadequate meiotic histone Deacetylation.
Nataliia Dolgopiatova - One of the best experts on this subject based on the ideXlab platform.
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Effect of Heterogeneous Deacetylation on the Properties of Northern Shrimp Chitin and Chitosan
KnE Life Sciences, 2020Co-Authors: Nataliia Dolgopiatova, Yuliya A. Kuchina, Tatiana Dyakina, Tatiana VolkovaAbstract:The effect of alkaline treatment of shrimp chitin on the molecular weight, the degree of Deacetylation and degree of crystallinity of the resulting chitosan is studied. The viscosity of chitosan solutions from repeatedly deacetylated chitin is studied. It is shown that repeated treatment of chitin/chitosan with alkali causes the destruction of polysaccharide macromolecules. After four-time Deacetylation and one-time Deacetylation of chitin/chitosan for four hours, the molecular weight of the polysaccharide decreases by ten times. The maximum degree of chitosan Deacetylation under experimental conditions was 92.0 -92.5%. The diffractograms of chitin and chitosan from the Northern shrimp are of the form typical for samples containing an amorphous phase in addition to a crystalline phase. The degree of crystallinity of chitin from Northern shrimp was 40.8%, of chitosan samples after one-, two-, and three-time Deacetylation was 62-65%. For a sample of chitosan obtained after four-time Deacetylation, recrystallization, and drying in a freeze dryer, the degree of crystallinity is close to the degree of crystallinity of shrimp chitin. The investigated acetic acid chitosan solutions with a concentration of 5% (wt.) and the chitosan molecular weight of 250, 160 and 130 kDa in their rheological properties are liquid-like non-Newtonian systems, their viscosity decreasing with increasing shear stress. After four-time Deacetylation of chitin, the viscosity of chitosan solutions practically does not change with increasing shear stress, which apparently can be due to a significant decrease in the molecular weight of chitosan under these conditions.
