Kinetic studies on the pyrolysis of chitin and chitosan

Tang, Wanjun; Wang, Cunxin; Chen, Donghua

doi:10.1016/j.polymdegradstab.2004.08.006

Cited by 259 publications

(138 citation statements)

References 25 publications

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“…Thermal degradation process of chitosan may be a random degradation of polymer chains and it was reported that the degradation starts from the scission of the C-O-C bond at a weak point [16]. Electrospinning and cross-linking has a strong influence on the amount of the amorphous phase present in the chitosan fiber mats [14].…”

Section: Thermal Degradation Kineticsmentioning

confidence: 99%

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Effect of neutralization and cross-linking on the thermal degradation of chitosan electrospun membranes

Correia

Gámiz-González

Botelho

et al. 2014

J Therm Anal Calorim

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Thermal degradation of as electrospun chitosan membranes and samples subsequently treated with ethanol and cross-linked with glutaraldehyde (GA) have been studied by thermogravimetry (TG) coupled with an infrared spectrometer (FTIR). The influence of the electrospinning process and cross-linking in the electrospun chitosan thermal stability was evaluated. Up to three degradation steps were observed in the TG data, corresponding to water dehydration reaction at temperatures below 100 ºC, loss of side groups formed between the amine groups of chitosan and trifluoroacetic acid between 150 -270 ºC and chitosan thermal degradation that starts around 250 ºC and goes up to 400 ºC. The Kissinger model was employed to evaluate the activation energies of the electrospun membranes during isothermal experiments and revealed that thermal degradation activation energy increases for the samples processed by electrospinning and subsequent neutralization and cross-linking treatments with respect to the neat chitosan powder.

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Section: Thermal Degradation Kineticsmentioning

confidence: 99%

“…It has been reported that the degradation of chitosan occurs in two separate steps, where the first step corresponds to dehydration and the second one to chitosan mass loss [16]. The first step is described as a result of the strong affinity of polysaccharides with water, as they can be easily hydrated [17].…”

Section: Introductionmentioning

confidence: 99%

Effect of neutralization and cross-linking on the thermal degradation of chitosan electrospun membranes

Correia

Gámiz-González

Botelho

et al. 2014

J Therm Anal Calorim

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“…Literature data shows that the thermal degradation of CS structure does not follow a single mechanism but is a complex reaction that gives different decomposition products [43][44][45][46] . The decomposition starts from a random scission pathway of C-O-C bond of the pyranose ring and is followed by a further formation of small molecules and volatile compounds including acetic acid, acetic anhydride, acetamide and aromatic heterocycles such as pyrazines, pyridines, pyrroles and furans.…”

Section: Resultsmentioning

confidence: 99%

Preparation and Characterization of Cross-Linked Chitosan Microcapsules for Controlled Delivery of Oxytetracycline

Larbi-Bouamrane¹,

Bal²,

Aliouche³

et al. 2016

pharmaceutical-sciences

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Larbi-Bouamrane, et al.: Preparation of Chitosan Microcapsules for Delivery of OxytetracyclineFormulations of encapsulated oxytetracycline in chitosan spherical beads have been developed in this work through the ionotropic gelation method in sodium tripolyphosphate or hexametaphosphate and characterized as drug delivery system to the gastrointestinal tract by Fourier transform infrared spectroscopy, thermal analysis and in vitro drug release in simulated gastric fluids. The Fourier transform infrared spectroscopy and differential scanning calorimetry measurements showed that tripolyphosphate and hexametaphosphate are cross-linked ionically to chitosan and there was no significant drug interaction between the entrapped drug and the carrying polymer. With respect to chitosan cross-linking features, sodium hexametaphosphate seems to give better swelling, higher diffusion and faster release kinetics, while addition of glutaraldehyde as a second cross-linking agent lowers the drug discharge. Release extent and kinetics were found to be pH dependent and approximated very well by the multistep models equations of Makoid-Banakar, PeppasSahlin and Korsmeyer-Peppas. Key words: Oxyteracycline, chitosan, encapsulation, crosslinking, release kineticsTetracyclines are broad spectrum antibiotics that exhibit activity against a wide range of Gram-positive and Gram-negative bacteria. Their favourable antimicrobial properties and the absence of major adverse effects have led to their extensive use in the therapy of human and animal infections [1][2][3][4] . Unfortunately, like the other antibiotic and as a result of the extensive prescription in conventional formulations, the emergence of microbial resistance has limited their effectiveness. So, other strategies are needed to keep tetracycline's and other antibiotics as resources for the next generation and to restore their initial antimicrobial activity. These strategies are based on the development of new classes of drugs with unique antibacterial mechanisms or new formulations enabling the reduction of amounts of antimicrobials used worldwide. In particular, investigation of new formulations has been carried out in order to overcome the disadvantages resulting from the administration of antibiotics in conventional forms [5][6][7] .The specific addressing of active molecules to the organ, tissue or cell is considered now as a major challenge and promising route for the treatment of various human diseases, including bacterial infections, cancer or genetic diseases [8] . New carrying and targeting approaches for drug delivery have been extensively studied in recent years. Most of them are centered on the development of nano-or micro-scale carrying systems [9][10][11] or specific molecules to improve and maximize drug bioavailability and hence therapeutic effects over a period of time. This highly selective approach would ensure an optimum response from the dosage form which significantly lowers the side effects and reduce treatment's expense.As non-conventional pharmaceutical dos...

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“…A variação de massa observada em uma análise termogravimétrica (Equação 1) é denominada de fração de conversão de massa. Onde, m 0 , m f e m t , são a massa inicial, a massa final e a massa em uma dado tempo ou temperatura de reação, respectivamente [10].…”

Section: Análise Cinética Do Processo De Degradação Térmicaunclassified

“…Os parâmetros T e R são, respectivamente, a temperatura absoluta e a constante dos gases ideais (8,31451 J/mol K) [10,11].…”

Section: Rtunclassified

Impacto do co-monômero hidroxivalerato na cinética de degradação térmica dos poli(3-hidroxialcanoatos)

2009

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: a djsouza@uenf.br , b eligio@uenf.br , c sanchez@uenf.br. RESUMOO objetivo deste trabalho foi avaliar o impacto que o conteúdo do co-monômero 3-hidroxivalerato exerce na cinética de degradação térmica de copolímeros P3(HB-x%HV). Filmes dos copolímeros, com diferentes conteúdos de co-monômero 3-hidroxivalerato, foram obtidos pela evaporação controlada de solvente, a partir de suas soluções em clorofórmio (1%m/m). Para o estudo termogramétrico (TGA), foram utilizados 10±0,3 mg de cada amostra, panelas de platina e atmosfera de He (100mL/min). O estudo cinético foi realizado em condições isotérmicas e não isotérmicas. Para as duas condições de análise, foi observado que os copoliésteres estudados apresentaram uma etapa de degradação definida em um curto intervalo de tempo. A análise da cinética do processo de degradação térmica, realizado segundo os métodos isoconversionais de Friedman e Ozawa-Wall-Flynn, indica que a energia de ativação envolvida no processo de degradação térmica é dependente da fração de conversão de massa. Tal dependência pode estar relacionada à ocorrência de clivagem de ligações covalentes com diferentes energias de ligação. Outro fator que pode contribuir para este comportamento é a diferença estrutural provocada pelos co-monômeros 3HB e 3HV. Os resultados obtidos indicam a necessidade de um controle na distribuição das unidades de 3HV, com vista a uma maior estabilidade térmica dos copolímeros. O aumento da estabilidade e, assim, da processabilidade destes copolímeros a partir do fundido, amplia as possibilidades de utilização destes poliésteres ambientalmente corretos. Palavras-chaves:Poli(3-hidroxialcanoatos), degradação térmica, cinética de degradação térmica. Impact of co-monomer hydroxyvalerate on thermal degradation kinetics of P3(HB-x% HV) copolymers ABSTRACTThe aim of this work was to evaluate the impact that the content of the co-3-hydroxyvalerate monomer has on thermal degradation kinetics of P3(HB-x%HV) copolymers. Films of the copolymers with different contents of 3-hydroxyvalerate were obtained by controlled evaporation of solvent from chloroform solution (1% m/m). Thermogravimetry study was carried out in helium atmosphere, platinum pans and sample mass about 10 ± 0.3 mg. The thermal degradation kinetic study was made on isothermal conditions and non-isothermal conditions. For the two conditions of analysis, it was observed that the copolyester studied presented a defined stage of degradation in a short time interval. The analysis of thermal degradation kinetics carried out by the isoconversional methods of Friedman and Ozawa-Flynn-Wall showed that the activation energy for the process of thermal degradation is dependent on the fraction of mass conversion. Such dependence may be related to the occurrence of cleavage of covalent bonds with different bonding energies. Other characteristic could be the structural differences caused by co-monomers 3HB and 3HV. The results obtained indicate the need to control the distribution of 3HV units to improve the thermal stability of the p...

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Kinetic studies on the pyrolysis of chitin and chitosan

Cited by 259 publications

References 25 publications

Effect of neutralization and cross-linking on the thermal degradation of chitosan electrospun membranes

Effect of neutralization and cross-linking on the thermal degradation of chitosan electrospun membranes

Preparation and Characterization of Cross-Linked Chitosan Microcapsules for Controlled Delivery of Oxytetracycline

Impacto do co-monômero hidroxivalerato na cinética de degradação térmica dos poli(3-hidroxialcanoatos)

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