Characteristics and thermal decomposition kinetics of wood-SiO₂composites derived by the sol-gel process

Abstract

Wood-SiO2 composites (WSiO2Cs) were prepared by means of the sol-gel process with methyltrimethoxysilane (MTMOS) as a reagent, and the physical properties, structure and thermal decomposition kinetics of the composites has been evaluated. The dimensional stability of the WSiO2Cs was better than that of unmodified wood, especially in terms of the weight percent gain (WPG), which achieved values up to 30%. The 29Si-NMR spectra show two different siloxane peaks (T2 and T3), which supports the theory about the formation of MTMOS network structures. Thermal decomposition experiments were also carried out in a TG analyzer under a nitrogen atmosphere. The apparent activation energy was determined according to the iso-conversional methods of Friedman, Flynn-Wall-Ozawa, modified Coats-Redfern, and Starink. The apparent activation energy between 10 and 70% conversion is 147–172, 170–291, 189–251, and 192–248 kJ mol−1 for wood and WSiO2Cs with WPGs of 10, 20, and 30%, respectively. However, the reaction order between 10 and 70% conversion calculated by the Avrami theory was 0.50–0.56, 0.35–0.45, 0.33–0.44, and 0.28–0.48. These results indicate that the dimensional and thermal stability of the wood could be effectively enhanced by MTMOS treatment.

Improvement of White Spruce Wood Dimensional Stability by Organosilanes Sol-Gel Impregnation and Heat Treatment

“…However, when adding these features, the chemical product is more expensive. In using methyltrimethoxysilane (MTMOS), interesting results were observed on Japanese cedar sapwood (Cryptomeria jopanica D. Don) [21] or with green elm (Ulmus L.) [22]. Indeed, treated wood showed a 75% decrease in water absorption and an improvement in dimensional stability of 72%-80%.…”

Catalyzed Reaction of Cellulose and Lignin with Methyltrimethoxysilane—FT-IR, 13C NMR and 29Si NMR Studies

“…Only minor signals were observed at −55.88 ppm (near-noise signal). The signals may correspond to linear groups called T 2 structures in the scientific literature [32]. In the silanization variant in which the reaction was conducted in the presence of an Al(acac) 3 catalyst (Figure 5a), significant differences were observed.…”

“…The signals correspond to carbon atoms of a Si–O–CH 2 methylene group (stemming from cellulose), a Si–O–CH 3 methoxy group (present in MTMOS) and a –CH 3 methyl group, respectively [33]. The presence of those signals could mean the presence of silicone compounds in the cellulose structure [32]. On the other hand, on the spectrum of 29 Si NMR (Figure 5a), intense peaks were observed at 57.04 and −66.10 ppm.…”

Utilization of Waste Bamboo Fibers in Thermoplastic Composites: Influence of the Chemical Composition and Thermal Decomposition Behavior

“…For various heating rates (β) and a given conversion rate (α), a linear relationship is observed by plotting log β versus 1/T, and the E a value is calculated from the slope of the straight line [31][32][33][34][35]. The reaction mechanism of the decomposition process is determined by the Criado method [28,36], which assumes that the Z m (α) master curves are a convolution of the functions f (α) and g(α) corresponding to the different models listed in Table 1 [37,38]: Table 1.…”