Perry N. Peralta

Dielectrophoresis of cellulose nanocrystals and alignment in ultrathin films by electric field-assisted shear assembly.

Ultrathin films of cellulose nanocrystals (CNCs) are obtained by using a convective assembly setup coupled with a low-strength external AC electric field. The orientation and degree of alignment of the rod-like nanoparticles are controlled by the applied field strength and frequency used during film formation. Calculated dipole moments and Clausius-Mossotti factors allowed the determination of the critical frequencies, the peak dielectrophoresis as well as the principal orientation of the CNCs in the ultrathin films. As a result of the combination of shear forces and low electric field highly ultrathin films with controlled, unprecedented CNC alignment are achieved.

Preliminary tests to evaluate the mechanical properties of young trees with small diameter

Abstract This paper describes methods developed to test the mechanical properties of small-diameter (3–10 mm) 1-year-old trees. Special test fixtures and procedures were designed to accommodate the small diameter and uneven shape of these young trees. The modulus of elasticity and strength in tension parallel to the grain, compression parallel to the grain, and bending were measured.

Effect of Lignin Genetic Modification on Wood Anatomy of Aspen Trees

The directed modification of specific traits of trees through genetic engineering provides opportunities for making significant genetic improvements to wood properties in matter of years instead of extended time frames required for traditional natural selection. An attractive target of forest- tree engineering is the modification of lignin content and lignin structure. While lower lignin content improves pulping efficiency, a decrease in lignin content could affect wood characteristics that are critical for solid wood use.After one year of growth in a greenhouse, a total of forty transgenic aspen (Populus tremuloides Michx.) with reduced lignin content and increased syringyl to guaiacyl ratio were harvested and diameter growth and cell morphology were investigated using quantitative wood anatomy and fiber quality analysis techniques. Comparing genetic groups to the wild-type as the control, similar radial growth and quantitative anatomical properties were observed for the genetic group with reduced lignin content. The genetic group with increased S/G ratio had lower diameter growth, lower vessel lumen diameter, but more numerous vessels. The combined effect of changes in lignin content and structure on radial growth and cell morphology seems to be more complex and gave inconsistent results.

Thermodynamics of Moisture Sorption by the Giant-Timber Bamboo

The thermodynamic interaction of water with giant-timber bamboo (Phyllostachys bambusoides Sieh. & Zucc.) was investigated. Thermodynamic properties were evaluated based on isosteric calculations from sorption isotherms at 20, 30, 40 and 50°C. The results show that. compared to wood, giant-timber bamboo exhibits less hygroscopicity and greater hysteresis. The differential heat of sorption. Q was found to be an exponential function of fractional moisture content, m, and decreased somewhat with increasing temperature. The relation Q s = (Q s ) o exp(-B 1 m) was considered to he reasonably adequate, but a better fit was provided by the equation Q s = A 2 + B 2 m + C 2 exp(-D 2 m) so that it was used in the calculation of the heat of wetting, W, and the integral heat of sorption, (W o - W). The differential heat of sorption at ovendry condition fell within the range observed for wood and other lignocellulosic material, The free energy, G., and the entropy, S., of sorbed water were in close agreement with those observed for wood, reconfirming the theory that definite enthalpy, free energy, and entropy changes accompany the sorption of water by lignocellulosic materials.

Distribution of wood polymers within the cell wall of transgenic aspen imaged by Raman microscopy

Abstract Little is known about the effect of genetic modification on the chemical composition and structure of wood, which could have a significant effect on reactivity during chemical and enzymatic processing. In this study, information was collected by confocal Raman microscopy (CRM) on the spatial distribution of lignin and polysaccharides in the cell wall of young transgenic aspen with reduced lignin content, increased syringyl/guaiacyl (S/G) ratio, and simultaneously reduced lignin content and increased S/G ratio. CRM revealed that the lignin content of the cell wall and compound middle lamella was reduced by the genetic modification. A higher volume of water was also found in the cell wall of transgenic aspen compared with wild-type aspen, indicating an increase in the hydrophilicity of the cell wall.

Fungal biodegradation of genetically modified and lignin-altered quaking aspen (Populus tremuloides Michx.)

Abstract Better access to wood carbohydrates as a result of reduced, or altered, lignin is a goal of biopulping, as well as biofuel research. In the present article, woods from three transgenic trees and one wild-type quaking aspen (Populus tremuloides Michx.) were analyzed in terms of mass loss of cellulose and lignin after incubation with lignocellulolytic fungi. The transgenic trees had reduced lignin content through transfer of an antisense -4CL gene, elevated syringyl/guaiacyl (S/G) ratio through insertion of a sense CAld5H gene and low lignin content and elevated S/G ratio through simultaneous insertion of -4CL and CAld5H genes, respectively. The lignocellulolytic fungi employed were a lignin-selective white rot fungus Ceriporiopsis subvermispora, a simultaneous white rot fungus Trametes versicolor and a brown rot fungus Postia placenta. Reduced lignin degradation was observed in woods with increased S/G ratios indicating that this analytical feature influences decay resistance, regardless of the fungal decay mechanism.

Elastic Modulus Determination of Transgenic Aspen Using a Dynamic Mechanical Analyzer in Static Bending Mode

The applicability of a dynamic mechanical analyzer (DMA) in determining the modulus of elasticity (MOE) of 2.5-year-old transgenic aspen (Populus tremuloides Michx.) was investigated. Fifty sample ...

An innovative wood-fiber composite incorporating nonwoven textile technologies.

This article is the first to describe a process of manufacturing engineered wood composites that combine two nonwoven textile technologies: bicomponent fiber and needle punching. Hardwood fiber was blended with 10 percent urea formaldehyde and formed into mats. The mats were sandwiched with polypropylene/polyester bicomponent fibers and then needle punched. Needle punching was done by means of barbed needles that oscillated in a vertical direction with regard to the surface of the fiber mat. The barbed needles mechanically interlaced the bicomponent web to the wood-fiber mat and pulled some of the polymer fibers through the thickness direction of the mat. During hot pressing, the polypropylene sheath of the bicomponent fiber flowed, bonded with adjacent wood fibers, and coalesced with the sheath of the adjacent bicomponent fibers. The mats were pressed until the urea formaldehyde was fully cured. Bending and tensile properties of the needle-punched wood composite were assessed and compared with medium-den...

Characterization and enzymatic hydrolysis of wood from transgenic Pinus taeda engineered with syringyl lignin or reduced lignin content

Softwood is an abundant resource; however, currently its utilization for bioconversion to obtain platform sugars is limited. Pinus taeda trees which were genetically modified to either produce S lignin or to decrease lignin content were characterized with a suite of analytic techniques. Syringyl lignin was visualized in the secondary xylem of one genetic line with Mäule staining. Solid-state nuclear magnetic resonance identified the S lignin units were coupled into the lignin through β-O-4 linkages, and thioacidolysis measured approximately 13% S lignin content in the same sample. Reductions of the lignin of as much as 33% were observed in the transgenics. To better understand how these modifications affect bioconversion, their amenability to hot water and dilute acid pretreatments and enzymatic hydrolysis was evaluated. Lignin reductions resulted in 1.9–3.2-fold increases in glucose release compared to the control. However, no apparent benefit was observed by S lignin incorporation at the concentrations reported in this study. These results highlight the potential for softwood cell wall properties to be improved for bioenergy/biochemical applications.

Wood: Diffusion and Permeability

Wood is increasingly used in the construction sector since it is environmentally friendly and cheap. To meet the high demands, accurate knowledge of wood and its properties is necessary. Thereby wood water relations are of great importance, due to the pronounced influence of moisture and moisture changes on mechanical properties as well as on dimensional changes. Nevertheless, the formulation of an accurate model for moisture transport in wood is a challenging task, which has motivated a lot of research effort. Moisture transport in wood is a diffusion process. This article provides an overview of molecular diffusion and permeability in wood. The recent developments in the formulation of models for moisture transport in wood and characterization of moisture content in wood are also presented.