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TGA and DSC data for untreated wood. (a) TG, DTG, and DDTG curves and definition of characteristic reaction temperatures; (b) combined TG and DSC curves and characteristic reaction temperature values.
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The effect of basic magnesium carbonate (BMC), magnesium hydroxide (MH), and magnesium chloride hydrate (MCH) on thermal degradation of red gum wood was studied using cone calorimetry, Thermogravimetric-differential scanning calorimetry (TG-DSC) analysis, and X-ray diffraction (XRD) characterization. The results showed common fire retardation actio...
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Context 1
... accurately separate different phases along the observed wood thermal degradation curve, some characteristic temperatures were defined as shown in of −d 2 Y/dt 2 = 0 in the second region. The beginning of the final and tailing region (also the end of the second region) dominated by lignin decomposition, is defined by the offset temperature, T OF-C , obtained by extrapolating the devolatilization rate corresponding to the local maximum in −d 2 Y/dt 2 values. The offset temperature for lignin, T OF-LG , is obtained by extrapolating the devolatilization rate corresponding to the local maximum in −d 2 Y/dt 2 values in the final region. (Figure 4b). The degradation process of the wood was separated into four stages from the established characteristic temperatures [14,16,[23][24][25]. The first stage from the beginning to about 150 ° C was drying stage, in which moisture desorption, and softening and melting of wax inclusion occurred. The second stage was from about 150 ° C to around 250 ° C, for dehydration from cellulose unit and decomposition of the extractives (i.e., pre-degradation stage). The third stage was combustion and charring stage, which is characterized by fast volatilization of wood and flaming combustion (258 to 390 ° C). The last stage was char calcination stage with temperatures ranging from 390 ° C to 650 ° C. Oxidation of residual char after flaming combustion resulted in glowing ignition of the char in this ...
Context 2
... TG, DTG, and DDTG curves of untreated wood sample are shown in Figure 4. The DTG curves showed two main regions of decomposition in an agreement with previous findings [20,21]. It has been shown [22][23][24] that hemicellulose component in wood started to decompose at about 225 ° C and is almost completely degraded at around 325 ° C. Cellulose was more stable and mainly degrades at temperatures between 315 ° C and 400 ° C, and lignin degraded slowly over a long broad range from about 200 ° C to over 400 ° C. Therefore, the first peak region in DTG curve was mainly due to the decomposition of hemicellulose, and the second region was mainly from cellulose. Decomposition of lignin followed to the end of degradation ...
Context 3
... validate this separation method, measured heat flow DSC curve of untreated wood is shown in Figure 4b in comparison with the corresponding TG data. The heat flow curve showed an endothermic peak at around 100 ° C, resulting from the heat absorption of water evaporation. With the temperature increase, the heat flow value increased and an exothermic peak appeared. Subsequently, the curve fell down and an intensive endothermic peak appeared around 370 ° C. The intensive endothermic peak at 370 ° C indicated that decomposition of wood in this stage absorbed heat (energy). Then the second exothermic presented around 430 ° C. The first and second peaks represented heat releases in pyrolysis of hemicelluloses and lignin, respectively [26]. The charring process was highly exothermal whereas volatilization was endothermal. Hemicellulose and lignin pyrolysis generated much higher solid residues, and the exothermal peaks observed in hemicellulose and lignin pyrolysis could be attributed to the charring. The full decomposition of cellulose might be attributed to the quick devolatilization reactions, leading to very few solid residues left [26]. It is clear that the temperatures for endothermic and exothermic peaks were in a good agreement with temperature values indicated by TG analysis, validating the separation method used. The TG curves of untreated and treated red gum wood samples were plotted ( Figure 5), and separated into different phases, with their characteristic temperatures listed in Table 2. MCH-treated wood started to degrade at around 130 ° C, and three obvious stages were presented on its DTG curve. The peak values were, respectively, around 133 ° C, 260 ° C, and 352 ° C, and a small shoulder around 340 ° C also presented. Based on the individual TG curves of MCH and wood, theoretical mass fraction data for MCH-treated wood was calculated and plotted according to the 15:85 mass ratios of MCH to wood ( Figure 6). The experimental TG curve showed an obviously more mass loss than that from the theoretical curve from 150 ° C to about 380 ° C, indicating MCH started to act on wood at 150 ° C. Although the onset point of the second peak for MCH-wood was about 324 ° C, the region around 260 ° C, rather than 323 ° C, was regarded as the beginning of combustion and charring stage since the MgCl 2 · 6H 2 O started to act at 260 ° C. ...
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