Effect of cupric ion on thermal degradation of chitosan

Abstract

The thermal degradation of chitosan and chitosan-cupric ion compounds in nitrogen was studied by thermogravimetry analysis and differential thermal analysis (DTA) in the temperature range 30-6008C. The effect of cupric ion on the thermal degradation behaviors of chitosan was discussed. Fourier transform-infrared (FTIR) and X-ray diffractogram (XRD) analysis were utilized to determine the micro-structure of chitosan-cupric ion compounds. The results show that FTIR absorbance bands of À ÀNÀ ÀH, À ÀCÀ ÀNÀ À, À ÀCÀ ÀOÀ ÀCÀ À etc. groups of chitosan are shifted, and XRD peaks of chitosan located at 11.3, 17.8, and 22.88 are gradually absent with increasing weight fraction of cupric ion mixed in chitosan, which show that there are coordinating bonds between chitosan and cupric ion. The results of thermal analysis indicate that the thermal degradation of chitosan and chitosancupric ion compounds in nitrogen is a two-stage reaction.The first stage is the deacetylation of the main chain and the cleavage of glycosidic linkages of chitosan, and the second stage is the thermal destruction of pyranose ring of chitosan and the decomposition of residual carbon, in which both are exothermic. The effect of cupric ion on the thermal degradation of chitosan is significant. In the thermal degradation of chitosan-cupric ion compounds, the temperature of initial weight loss (T st ), the temperature of maximal weight loss rate (T max ), that is, the peak temperature on the DTG curve, and the peak temperature (T p ) on the DTA curve decrease, and the reaction activation energy (E a ) varies with increasing weight fraction of cupric ion.

Chitosan, sisal cellulose, and biocomposite chitosan/sisal cellulose films prepared from thiourea/NaOH aqueous solution

“…2b). Theses peaks could be due to the chain deacetylation and to decompositions involving the main chain (Ou et al, 2008). A thermal decomposition step followed by volatilization of by products could be detected both as endothermic or exothermic peaks, depending on the balance between both processes.…”

“…This could be due to the decomposition of acetylated units, already correlated to an endothermic process (Nieto & Peniche-Covas, 1991). In the literature various remarks were made on the thermal decomposition of chitosan, since only exothermic (Ou et al, 2008) or only endothermic (Chuang, Young, Yao, & Chiu, 1999) peaks were mentioned. The thermal properties of chitosan are dependant on degree of acetylation, crystallinity, average molecular weight and probably are at the origin of the different data found in the literature.…”

Biobased films prepared from NaOH/thiourea aqueous solution of chitosan and linter cellulose

“…The DSC curve for the chitosan film obtained after dissolution in NaOH/thiourea (Almeida et al 2010) showed two peaks, an endothermic peak at 225°C and an exothermic peak near 275°C. These peaks are probably related to the deacetylation of the chain and to decompositions involving the main chain (Ou et al 2008).…”

Morphological, Thermal and Electrical Studies on Chitosan Heavy Metal Complexes

“…10-12 show thermal gravimetric analysis (TGA) of chitosan and chitosanmetal complexes (Ch-Fe, Ch-Co, and Ch-Ni) [16] in three different ratios indicated that chitosan and chitosan-metal complexes proceed in two stages: the first stage explained the water weight loss, while the second one is the degradation of chains with greater weight loss, Table (2) shows the weight loss percentages of two stages for chitosan and chitosan-metal complexes. …”

“…Determination of activation energy of decomposition of chitosan and chitosanmetal complexes [16] The activation energy was determined by the Arrhenius relationship according to Broido method in Eq.1. (1) where Ea is the activation energy (J mol Electrical conductivity measurements of chitosan and chitosan-metals ions complexes [19,20] The electrical conductivity (σ) was calculated from Eq.3…”