Roger M. Rowell

A simplified procedure for the acetylation of hardwood and softwood flakes for flakeboard production.

Abstract Southern pine and aspen flakes were acetylated with acetic anhydride alone without cosolvent or catalyst by a simple dip procedure. The new procedure greatly shortens reaction time and simplifies chemical recovery. Acetylation weight gains of 15% to 20% can be achieved in 1 to 3 hours with southern pine flakes and in 2 to 4 hours with aspen flakes. Flakeboards made from acetylated southern pine or aspen flakes absorbed much less water, both in water-soaking tests and when subjected to humid air, and swelled at a lower rate and to a lower extent than did control boards. Hygroscopicity of the resulting flakeboards decreased with increased level of wood acetylation. The equilibrium moisture content (EMC) for flakeboards made from acetylated flakes was lower at each relative humidity tested than that of control boards.

Utilization of byproducts from the tequila industry: part 1: agave bagasse as a raw material for animal feeding and fiberboard production

Agave bagasse was successfully separated into fractions that were used in sheep feeding trials. Agave bagasse can be substituted for corn stubble in the sheeps diet which resulted in improved weight gain. Agave bagasse was also processed into long and short fiber fractions with a hammermill and fiberboards of medium and high specific gravities being produced. Medium specific gravity agave fiberboards had moisture and mechanical properties comparable to medium specific gravity fiberboards made using aspen fiber. All high specific gravity agave fiberboards made from short or long fibers were stronger in bending than the ANSI standard for hardboards.

Swelling of wood. Part II. Swelling in organic liquids

The rate and maximum swelling of several North American wood species in 40 organic liquids have been obtained with a computer interfaced linear variable displacement transformer. Since wood swells very fast in some organic liquids, even at room temperature, this apparatus made it possible to obtain accurate rate data on the swelling of wood in organic liquids. It was found that many similarities existed between wood and cellulose maximum swelling within various solvent chemical classes. Hence, it appears that cellulose is the primary wood polymer responsible for the major amount of swelling of wood (...)

Understanding decay resistance, dimensional stability and strength changes in heat treated and acetylated wood

Abstract Reductions in hygroscopicity, increased dimensional stability and decay resistance of heat-treated wood depend on decomposition of a large portion of the hemicelluloses in the wood cell wall. In theory, these hemicelluloses are converted to small organic molecules, water and volatile furan-type intermediates that can polymerize in the cell wall. Reductions in hygroscopicity and improved dimensional stability of acetylated wood depend on esterification of the accessible hemicelluloses in the cell wall reducing hydrogen bonding with water and bulking the cell wall back to its green volume. Stability is not 100% since the water molecule is smaller than the acetyl group so water can access hydroxyl sites even when the wood is fully acetylated. The cell-wall moisture content is too low in acetylated wood to support fungal attack so the initial enzymic attack starting the colonization does not take place. Strength properties are reduced in heat-treated wood owing to the degradation of the cell-wall matrix resulting from the hemicellulose loss. Strength properties are not significantly changed in acetylated wood and acetylation results in greatly improved wet strength and wet stiffness properties.

Swelling of wood

SummaryThe rate and maximum swelling of several North American wood species in water have been obtained with a computer interfaced linear variable displacement transformer. Since wood swells extremely fast in water even at room temperature, this apparatus made it possible for the first time, to obtain accurate rate data on the swelling of wood in water. The strict linear dependence of swelling on the temperature suggests a chemical mechanism. The activation energies obtained from Arrhenius plots ranged from 32.2 KJ/mole for sitka spruce to 47.6 KJ/mole for sugar maple. Although the two hardwoods exhibited greater maximum tangential swelling compared with the two softwoods, the maximum swelling appears to be correlated with the wood density. Generally both the rate and maximum swelling of the woods were increased by removal of extractives and the activation energies were reduced.

Removal of Heavy Metal Ions from Aqueous Solutions Using Lignocellulosic Fibers

Abstract Spruce, coconut coir, sugarcane bagasse, kenaf bast, kenaf core, and cotton were tested for their ability to remove copper, nickel and zinc ions from aqueous solutions as a function of their lignin content. The fibers were analyzed for sugar and lignin content and extracted with di-ethyl ether, ethyl alcohol, hot water, or 1% sodium hydroxide. The order of lignin content in un-extracted fibers is coconut coir > spruce > kenaf core > bagasse > kenaf bast > cotton. The fiber with the highest level of heavy metal removal was kenaf bast that had a very low level of lignin, showing that removal of heavy metals does not correlate with lignin content. Cotton, with about 1% lignin, was very low in metal ion sorption while all of the fibers containing lignin did remove heavy metal ions showing that lignin does play a role in metal ion sorption. Extraction with the various solvents removed different cell wall components and did change heavy metal sorption that indicates that cell wall chemistry and architecture may also be important factors in the sorption of heavy metals from aqueous solutions using lignocellulosic fibers.

Utilization of by-products from the tequila industry. Part 2: potential value of Agave tequilana Weber azul leaves

The leaves of the agave plant are left in the field after harvesting the heads for tequila production. Different types of agave leaves were isolated, classified, and their content in the total plant determined. The usable fractions were collected and their properties determined. Of the total wet weight of the agave plant, 54% corresponds to the agave head, 32% corresponds to materials which could be usable for sugar and fiber production which leaves 14% of the wet plant without apparent utility. The fractions with higher total reducing sugars (TRS) content were the fresh fraction of partially dry leaves stuck to the head and the leaf bases with a TRS content of 16.1% and 13.1%, respectively. The highest TRS concentration (16-28%) is in the agave head which is used for tequila production. The leaves are 90-120 cm long and 8-12 cm wide and contain fiber bundles that are 23-52 cm long and 0.6-13 mm wide. The ultimate fiber length is approximately 1.6 mm with an average width of 25 microns. There are several types of leaf fibers that can be utilized depending on what part of the plant they come from and what product is desired. Agave leaf fibers were pulped using a soda pulping process and the pulp was hand formed into test sheets. Test sheets made from pulped agave leaf fibers had a breaking length comparable to paper made from both pine and eucalyptus fibers, but the tear index and burst index were lower than the other two papers.

Swelling of compressed cellulose fiber webs in organic liquids

Maximum liquid-holding capacities of various compressed fibers in water and in a series of various organic liquids have been investigated. The maximum liquid-holding capacity versus bulk density relationships gave polynomial curves, generally with a peak. Good relative correlations for cellulose, compressed fiber pellets and wood were found for the series of liquids tested. In general, liquids that swelled wood to a low to medium range (up to 6%) did not swell appreciablyα-cellulose and sulfite pulp, while good to excellent wood-swelling agents swelled all the fibers very significantly. It was also found that the hydrogen-bonding parameter of the swelling liquid was the most important factor. The swelling rate of various compressed fiber systems in organic liquids was dramatically increased by raising the temperature. Activation energies and molar volume of the swelling liquid were linearly correlated.

Thermoplasticization of bagasse. I. Preparation and characterization of esterified bagasse fibers

This research was to investigate the conversion of bagasse into a thermo- formable material through esterification of the fiber matrix. For this purpose, bagasse was esterified in the absence of solvent using succinic anhydride (SA). The reaction parameters of temperature reaction, time, and amount of succinic anhydride added were studied. Ester content, Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA) were used to characterize the chemical and thermal proper- ties of the esterified fibers. The results showed that on reacting bagasse with SA in the absence of solvent, ester content up to about 48% could be obtained. Diester formation increased with increasing reaction time and temperature at high levels of ester content. Ester content determination of the esterified fibers and their corresponding holocellu- loses showed that the reaction took place in the lignin and holocellulose components of bagasse. The IR results showed that the crystallinity index of different esterified bagasse samples did not decrease as a result of increasing the ester content. DSC and TGA results showed that esterified-bagasse fibers were less thermally stable than the untreated fibers, DMTA results showed that esterification of the fibers resulted in a decrease in the tan δ peak temperature of the esterified fibers compared to the un- treated fiber.