The thermal expansion of cellulose, hemicellulose, and lignin

Ramiah, M. V.; Goring, D. A. I.

doi:10.1002/pol.1966.150040813

Cited by 12 publications

(18 citation statements)

References 8 publications

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“…There are two factors associated with the higher WL of hardwoods compared to softwoods: (1) Hardwoods are less thermally stable than softwoods. Ramiah and Goring (1967) studied the thermal degradation of isolated birch xylan and a spruce glucomannan, by determining the rate of gas evolution from the heated samples. These experiments showed that the hardwood xylan was less thermally stable than the softwood hemicelluloses, (2) The hemicellulosic content and composition in hardwoods have higher acetyl content than softwoods (Fengel and Wegener 1984).…”

Section: Resultsmentioning

confidence: 99%

Influence of hot water extraction on cell wall and OSB strand mechanics

et al. 2017

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The exposure of wood to elevated temperatures during hot water extraction (HWE) has been shown to significantly influence a variety of physical and chemical properties of the wood. Aspen (Populus tremuloides) and hemlock (Tsuga canadensis) strands underwent HWE at 160°C for four different periods of time. The weight loss (WL) associated with the processes ranged from 2.9 to 17.3% for the aspen, and from 2.9 to 12.8% for the hemlock. The higher WL associated with the hardwood was attributed to higher hemicellulose content in the hardwood than in the softwood as well as differences in chemical composition. Substantial increases in cell wall hardness (up to 34%) and modulus of elasticity (MOE) (up to 28%) were obtained at the intermediate extraction conditions. Extended exposure conditions resulted in decreases. The axial MOE of strands showed significant differences only in aspen. These changes are hypothesized to be related, in part, to changes in cellulose crystallinity.

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Section: Resultsmentioning

confidence: 99%

Influence of hot water extraction on cell wall and OSB strand mechanics

et al. 2017

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“…In this temperature region, the secondary relaxation in the glassy state has been detected by dilatometry at 80-100°C for cellulose, hemicellulose, and lignins (Ramiah and Goring 1965), at 105°C for cellulose triacetate (Mandelkern and Flory 1951), and at 155°C for cellulose acetate (Russel and Van Kerpel 1957). This relaxation was assigned to the rapture of weak hydrogen bonds (Ramiah and Goring 1965). At approximately 300°C, there was sharp decrease in E 0 , and there was a tan d peak at 320°C.…”

Section: Process Imentioning

confidence: 96%

“…This relaxation may be caused by the elimination of absorbed water (Pizzoli et al 1987;Scandola and Ceccorulli 1985) or glass transition of cellulose plasticized by absorbed water. In this temperature region, the secondary relaxation in the glassy state has been detected by dilatometry at 80-100°C for cellulose, hemicellulose, and lignins (Ramiah and Goring 1965), at 105°C for cellulose triacetate (Mandelkern and Flory 1951), and at 155°C for cellulose acetate (Russel and Van Kerpel 1957). This relaxation was assigned to the rapture of weak hydrogen bonds (Ramiah and Goring 1965).…”

Section: Process Imentioning

confidence: 99%

Preparation and mechanical properties of bacterial cellulose nanocomposites loaded with silica nanoparticles

et al. 2007

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Bacterial cellulose (BC), which is produced by Gluconacetobacter xylinus (Ga. xylinus) in culture, is made up of a three-dimensional network of ribbon-shaped bundles of cellulose microfibrils. In the current studies, we used two processes to prepare nanocomposites of BC filled with silica particles. In Process I, Ga. xylinus was incubated in medium containing silica sol Snowtex 0 (ST 0, pH 2-4) or Snowtex 20 (ST 20, pH 9.5-10.0). The elastic modulus at 20°C was improved by keeping the amount of silica in the nanocomposites below 4% when ST 20 was used and below 8.7% when ST 0 was used. This process allowed incorporation of 50% silica in BC. Inclusion of higher amounts of silica reduced the modulus at 20°C and the strength of the nanocomposites below that of BC. X-ray diffraction measurements revealed that the silica particles disturb the formation of ribbon-shaped fibrils and affect the preferential orientation of the (110) plane. We also produced BC-silica nanocomposites by Process II, wherein the BC hydrogel was immersed in different concentrations of silica sols, allowing silica particles to diffuse into the BC hydrogel and lodge in the spaces between the ribbon-shaped fibrils. This method increased the modulus at 20°C and the strength compared to the BC matrix, but it was difficult to load the BC with more than 10% silica in this way.

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“…8,10 The floatation method, involving suspending crystals in a density gradient composed of a material in which the crystal is insoluble, is capable of high precision and does not demand sophisticated equipments, 8 but gas pycnometry, in which volume of a solid impermeable to helium is measured, is also capable of high precision, 11 is convenient in the sense that commercial equipment is readily available, and is likely more suitable for investigation of amorphous powders, although the floatation method has been used with synthetic polymers. 12 Although there are numerous uses of gas pycnometry in the literature, nearly all of the previous work, including a detailed study of errors and precision, 11 has focused on crystalline materials. Amorphous materials, particularly high surface area hygroscopic freezedried materials, present special problems because of residual water retention and the resulting errors introduced.…”

Section: Introductionmentioning

confidence: 99%