Glass transition temperature and thermal decomposition of cellulose powder

Abstract

Cellulose powder and cellulose pellets obtained by pressing the microcrystalline powder were studied using differential scanning calorimetry (DSC), differential thermal analysis (DTA), and thermal gravimetry (TG). The TG method enabled the assessment of water content in the investigated samples. The glass phase transition in cellulose was studied using the DSC method, both in heating and cooling runs, in a wide temperature range from -100 to 180°C. It is shown that the DSC cooling runs are more suitable for the glass phase transition visualisation than the heating runs. The discrepancy between glass phase transition temperature T g found using DSC and predictions by Kaelbe's approach are observed for ''dry'' (7 and 5.3% water content) cellulose. This could be explained by strong interactions between cellulose chains appearing when the water concentration decreases. The T g measurements vs. moisture content may be used for cellulose crystallinity index determination.

Change in dielectric relaxation with the presence of water in highly filled composites

“…However, the shift in the glass transition temperature of the wet resin system shows a confinement effect as discussed by Arndt et al 47 for salol relaxation dynamics in nanometer size pores; the relaxation rate of the confined material increased compared to bulk material. Some other examples of observed low T g with moisture/ water content can be found in the literature, 10,11,48 where change in the glass temperature was reported for inulin, epoxy resins and cellulose. The epoxy system studied 11 showed that the glass transition estimated from the mechanical modulus shifted to lower temperatures with different moisture treatment with shift related to the moisture weight gain, which we have not included in this work.…”

“…6 The presence of water and its influence in the dielectric response were previously studied in various polymeric systems. [7][8][9][10][11] Here, we concentrate on the change in the dielectric properties of highly filled composites in the presence of water, and report on the dielectric relaxation of moisture-absorbed and dry samples.…”

“…The method has been applied to various different material systems. [7][8][9][10][11][20][21][22] Electrical properties of materials can be determined from the impedance measurements by performing current measurements with applied voltage and using the geometrical capacitance C 0 , the geometry of the sample. For example, for the complex permittivity, " Ã is estimated from the current measurement as a complex capacitance C Ã for a given geometrical shape of the measurement electrodes, which determine the geometrical capacitance C 0 , Here, the angular frequency, !, independent material properties are of relative permittivity at high frequencies, " 1 , and Ohmic (direct-current) conductivity, 0 ; ı ¼ ffiffiffiffiffiffi ffi À1 p .…”

Influence of hydrogen bonds on glass transition and dielectric relaxations of cellulose

“…Thermal stability has been characterized by thermogravimetry analysis (TGA) [10] and physical structure by differential scanning calorimetry (DSC) [11]. In the literature, thermogravimetry analyses of cellulose point out two weight losses; the first one in the range of 40 to 80°C attributed to the water evaporation [11][12][13] and the second one in the temperature range of 200 to 400°C, to polymer degradation.…”

“…In the literature, thermogravimetry analyses of cellulose point out two weight losses; the first one in the range of 40 to 80°C attributed to the water evaporation [11][12][13] and the second one in the temperature range of 200 to 400°C, to polymer degradation. During this decomposition, the principal products are water and carbon dioxide [5,11,12,14,15].…”