VTechWorks Repository :: Browsing by Author "Glasser, Wolfgang G."

Browsing by Author "Glasser, Wolfgang G."

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3D printing of lignin: Challenges, opportunities and roads onward
Ebers, L. -S.; Arya, Aditi; Bowland, C. C.; Glasser, Wolfgang G.; Chmely, S. C.; Naskar, A. K.; Laborie, Marie-Pierre Genevieve (2021-06)
As the second most abundant biopolymer on earth, and as a resource recently becoming more available in separated and purified form on an industrial scale due to the development of new isolation technologies, lignin has a key role to play in transitioning our material industry towards sustainability. Additive manufacturing (AM), the most efficient-material processing technology to date, has likewise made great strides to promote sustainable industrial solutions to our needs in engineered products. Bringing lignin research to AM has prompted the emergence of the nascent "lignin 3D printing" field. This review presents the recent state of art of this promising field and highlights its challenges and opportunities. Following a review of the industrial availability, molecular attributes, and associated properties of technical lignins, we review R&D efforts at implementing lignin systems in extrusion-based and stereolithography (SLA) printing technologies. Doing so underlines the adage of lignin research that "all lignins are not created equal," and stresses the opportunity nested in this chemical diversity created mostly by differences in isolation conditions to molecularly select and tune the attributes of technical lignin systems towards desirable properties, be it by modification or polymer blending. Considering the AM design process in its entirety, we finally propose onward routes to bring the full potential to this emerging field. We hope that this review can help promote the unique value and overdue industrial role of lignin in sustainable engineered materials and products.
Alkylene oxide esters of lignin sulfonic acid
(United States Patent and Trademark Office, 1992-04-07)
Lignin sulfonates are converted into sulfonic acid esters by blocking free phenolic hydroxyl groups on the lignin sulfonates from reaction with a suitable protective group, subjecting the blocked lignin sulfonate in aqueous solution to ion exchange to produce the free sulfonic acid thereof, exchanging the aqueous solvent into a polar organic solvent, such as isopropanol, and reacting the sulfonic acid derivative in the polar organic solvent with a saturated or unsaturated aliphatic epoxide, preferably an alkylene oxide. The resulting sulfonic acid ester adduct may be isolated and purified from the reactants using solvent extraction. Lignin sulfonic acid ester adducts are produced that are soluble in a variety of organic solvents and insoluble in water.
Analysis of wood pulp extracts utilizing gas chromatography-mass spectroscopy
Sequeira, Anna J. (Virginia Tech, 1991)
Wood pulp mill effluents continue to attract much attention due to environmental consequences. However, in comparison, very little work has been published on wood pulp extracts themselves. In this investigation, chemithermomechanical (CTMP) pulps as well as Kraft (BKP) pulps were Soxhlet extracted with solvents of different polarity. These two types of pulp extracts were then compared qualitatively using GC-FID and GC-MSD as well as quantitatively based on the percent of extractives obtained. For all the pulps studied, the percent extractives of water > ethyl acetate > cyclohexane. The CTMP extracts exhibited many more components as compared to BKP extracts for all the extractions solvents. The presence of trace chlorinated phenolics in the above wood pulp extracts was also addressed utilizing GC-ECD, GC-EIMS and GC-NCIMS. 4-MCG, 4,5-DCG, 4,5,6-TCG, 3,4,5-TCG, 2,4,6- TCP, 2,3,4,6-TeCP, PCP and 6-MCVN were discovered. Due to a lack of knowledge of the complete history of the wood pulps studied, the exact causes for their discoveries are unknown. Attempts were also made to study the feasibility of Supercritical Fluid Extraction of the above mentioned wood pulps due to the difficulties faced with Soxhlet extractions. The percent extractives obtained using SF-CO₂ and cyclohexane were found to be comparable.
Aspects of amidization of chitosan
Toffey, Ackah (Virginia Tech, 1996)
The intent of this research was to develop an understanding of an amidized chitosan-from-chitosan regeneration process discovered in our laboratory. In this study several characterization methods including DMTA, TMA, TGA, X-ray diffraction, FTIR, solid state CP-MAS ¹³C NMR, and HPLC were used to study the transformation of various ionic complexes of chitosan (N-acylate) to their respective N-acyl homologs of chitosan; and several properties of these materials were examined. DMTA and TMA provided information on changes in T_g as well as modulus-changes and glass formation underlying the transformation of the N-acylate to the N-acyl derivative. X-ray diffraction and FTIR shed some insights on the morphology of the N-acetyl homolog of chitosan in relation to native chitin. Solid state CP-MAS ¹³C NMR provided evidence of the conversion of N-acylate to N-acetyl. Enzymatic hydrolysis of native chitin and amidized chitosan homologs and subsequent identification of fractions by HPLC allowed a comparison of various amidized chitosan homologs in terms of their recognition and degradation by chitinolytic enzymes. Solid state CP-MAS ¹³C showed that the heat treatment of the ionic complex of chitosan results in thermal dehydration leading to the formation of the N-acetyl group at the C-2 of chitin. The DS of amidized chitosan varied between 0.1 and 0.6. T_g-changes with time and heating temperature were used as a variable to monitor amidization. Kinetics analysis indicated that the amidization of various ionic complexes of chitosan is a first order, two-phase process with activation energies of 14±1 kcal/mol and 21±2 kcal/mol for the first and second phase, respectively. These values did not vary with the type of acid used in the formation of the chitosan complex. This two-phase behavior is explained with the influence of vitrification on chain mobility. In situ DMTA was found to be a suitable technique for monitoring the phase transformation of chitosonium acetate and chitosonium propionate from a rubbery to a glassy phase (vitrification). Consequently, the concept of TTT-cure diagram analysis was used to describe such phase changes and map out vitrification and full cure curves. As in thermosets, the vitrification curve describing glass formation in these materials is S-shaped. The time to full cure decreased with increasing heating temperature. The activation energy for vitrification is the same irrespective of the type of acid used in the preparation of chitosan complex. Thermal analysis revealed that the T_g of N-acyl homologs of chitin displays a stepwise relationship with length of N-acyl substituent. These materials are characterized by two transitions designated as β- and α-relaxation. Additionally, enzymatic hydrolysis of N-acyl homologs of chitosan using an enzyme mixture of chitinase, chitosanase, and β-N-acetylglucosaminidase and subsequent identification of fractions revealed that these enzymes recognize and degrade chitin irrespective of the N-acyl substituent at the C-2 position of chitin at any DS.
Aspects of Wood Adhesion: Applications of 13C CP/MAS NMR and Fracture Testing
Schmidt, Robert G. (Virginia Tech, 1998-01-28)
Phenol Formaldehyde (PF) and polymeric isocyanate (pMDI) are the two main types of adhesives used in the production of structural wood-based composites. Much is unknown about various aspects of adhesion between these two types of resins and wood. The present research describes the development of techniques which will permit an enhanced understanding of 1.) the extent of cure of PF within a wood based composite, 2.) the scale of molecular level interactions between PF and pMDI and wood, 3.) mechanical performance and durability of wood-adhesive bonds. Correlations were established between conventional methods of characterization of neat PF (thermomechanical analysis, swelling studies) and measurements made using 13C CP/MAS NMR. These correlations were then utilized to characterize PF cured in the presence of wood. The use of 13C labeled PF allowed estimates of relative degrees of resin conversion to be made. The use of 13C and deuterium labeled PF allowed qualitative estimates of resin molecular rigidity to be made. The scale of molecular level interactions between PF and pMDI and wood was probed using NMR relaxation experiments. Evidence was shown to suggest the formation of an interpenetrating polymer network (IPN) morphology existing at both types of wood-resin interphases. The formation of the IPN morphology was strongly influenced by resin molecular weight, cure temperature and the presence of solvent. A new test geometry for the evaluation of the fracture toughness of wood-adhesive bonds was developed. Consistent and reliable results were obtained. It was found that low molecular weight PF possessed enhanced durability over high molecular weight.
Blends of Biodegradable Thermoplastics With Lignin Esters
Ghosh, Indrajit (Virginia Tech, 1998-04-22)
Thermoplastic blends of several biodegradable polymers with lignin (L) and lignin esters were prepared by solvent casting and melt processing. Among the biodegradable thermoplastics were cellulose acetate butyrate (CAB), poly-hydroxybutyrate (PHB), poly-hydroxybutyrate-co-valerate (PHBV), and a starch-caprolactone blend (SCL). Lignin esters included acetate (LA), butyrate (LB), hexanoate (LH), and laurate (LL). Blend characteristics were analyzed in terms of thermal and mechanical properties. The results indicate widely different levels of interaction between two polymer constituents. Melt blended samples of CAB/LA and CAB/LB were compatible on a 15-30 nm scale when probed by dynamic mechanical thermal analysis, and the glass transition temperatures of the blends followed Fox equation, whereas those of CAB/LH and CAB/LL showed distinct broad transitions on the same scale. Melt blending produced well dispersed phases whereas large phase separation evolved out of solvent castings. Crystallinity and melting points of PHB and PHBV were affected by the incorporation of lignin component, revealing some interaction between the blend constituents. Blends of SCL with L and LB revealed significant effect on crystallinity and melting temperatures of poly-caprolactone component, revealing polymer-polymer interaction between SCL and lignin components. An increased degree of crystallinity was observed in the case of higher-Tg L compared to lower Tg LB. Improvememt in modulus (and in some cases strength also) was observed in almost all blends types due to the glassy reinforcing behavior of lignin.
Cellulose derivatives with a low degree of substitution
(United States Patent and Trademark Office, 1996-06-04)
The invention is directed to the formation of cellulose derivatives using homogenous phase reaction conditions. Cellulose is dissolved using DMAc/LiCl and a reagent system is added to promote the acylation of an appropriate acid anhydride or free carboxylic acid. One reagent system includes N,N-dicyclohexylcarbodiimide (DCC) and 4-pyrrolidinopyridine (PP). Another reagent system includes p-toluene sulfonyl chloride (TsCl) and pyridine (Py).
Cellulose fiber reinforced thermoplastic composites: Processing and Product Charateristics
Taib, Razaina Mat (Virginia Tech, 1998-05-18)
Steam exploded fibers from Yellow Poplar (Liriodendron tulipifera) wood were assessed in terms of (a) their impact on torque during melt processing of a thermoplastic cellulose ester (plasticized CAB); (b) their fiber incorporation and dispersion characteristics in a CAB-based composite by SEM and image analysis, respectively; and (c) their impact on the mechanical properties (under tension) of CAB-based composites having fiber contents of between 10 and 40% by weight. The fibers included water-washed steam exploded fibers (WEF), alkali-extracted fibers (AEF), acetylated fibers (AAEF), all from Yellow poplar (log Ro = 4.23), and oat fillers (COF) as control. The stepwise increase in cellulose content by extraction, and especially the (surface) modification by acetylation, contributed to increased torque during melt processing, and to improved interfacial adhesion as well as fiber dispersion. As compared to pure CAB, AAEF generated the highest increase in torque (+ 421%) followed by AEF (+ 260%) and WEF (+ 190%) at 40% fiber content by weight. AAEF was also found to enhance the tensile properties of the resulting composites. SEM studies of the tensile fracture surfaces indicated significant interfacial delamination and also pull - out of fibers when WEF, AEF, and COF were used to reinforce the CAB matrix. Composites with AAEF, by contrast, revealed fracture surfaces with reduced interfacial delamination and with significant fiber fracturing during failure. Image analysis was used to determine fiber dispersion within the resulting composites quantitatively. Significant improvement in fiber dispersion was achieved when the matrix was reinforced with acetylated fibers (AAEF). Fiber addition to the matrix resulted in loss of strain at break (- 80 to - 93%) and slight or significant increases in modulus (+ 47 to + 103%) depending on fiber type at 40% fiber content. Maximum stress declined for all fibers except AAEF at all fiber contents. AAEF-based composites revealed a decline in maximum stress when fiber content rose to 10%, and this reversed when fiber content increased beyond 10%. This increase in strength is consistent with the rule of mixtures that stipulates reinforcement of the matrix by fibers that are capable of transferring stresses across the fiber-matrix interface. All fibers suffered length decreases during melt processing.
Cellulose-based fibers from liquid crystalline solutions
Davé, Vipul (Virginia Tech, 1992-02-05)
Solutions of cellulose esters with different concentrations in dimethylacetamide (DMAc) and with different types of substituents were studied in relation to their liquid crystalline (LC) solution behavior. Classical LC behavior was revealed for all solutions. Critical polymer concentration (V_p^c) is highest for cellulose acetate (CA) and lowest for cellulose acetate butyrate (CAB) with highest degree of butyration. This is opposite to the classical model by Flory which predicts an increase in V_p^c with decreasing aspect ratio (L/d). Fibers were spun from isotropic and anisotropic DMAc solutions of cellulose esters by dry jet/wet spinning process. The mechanical properties, orientation, and crystallinity of the fibers increased as spinning progressed from the isotropic to the anisotropic solution state. High butyryl content enhances both overall solubility and the formation of LC solutions at lower concentration, but it results in lower fiber properties. Unmodified cellulose (C) and cellulose hexanoate (CH) also exhibited LC behavior. The V_p^c value for CH was lower than that obtained for CAB with maximum degree of butyration. This indicates that bulky substituents may lower V_p^c values. The formation of high modulus (152 g/d) cellulose fibers from LC solutions is attributed to the air-gap that exists in the dry jet/wet spinning process. Presence of lithium chloride (LiCl) in the LC solutions of CAB exhibited ionic interactions. Mechano-sorptive creep behavior of the fibers spun from these solutions decreases in the presence of residual LiCl salt. Fibers from blends of CAB and of C with lignin (L) were spun from Lc solution. Morphological investigations demonstrate that CAB and L formed intimately mixed blends whereas C and L were partially mixed. The mechanical properties of the fibers with L increased due to good phase mixing of CAB and L molecules in the fiber matrix.
Characterization of lignin deposition in Pinus taeda L. cell suspension cultures
Eberhardt, Thomas Leonard (Virginia Tech, 1992-03-05)
Pinus taeda L. suspension culture cells were used to develop a model system to study the process of lignification occurring during the early stages of cell wall formation and maturation. Chemical, biochemical and histochemical analyses of the P. taeda suspension cultures grown with 2,4-dichlorophenoxyacetic acid (2,4-D) as the growth regulator did not provide conclusive evidence for lignin deposition. On the other hand, cultures in which 2,4-D was substituted with Î±-naphthaleneacetic acid (NAA) were shown to lignify. During this induction of lignification, limited cell wall thickening occurred since transmission electron microscopy of the 2,4-D grown cells showed only primary walls while the average cell wall thickness of the NAA-grown cells was consistent with secondary (S₁) layer formation. Despite the possibility of only limited lignin deposition in the 2,4-0 grown cells, secondary metabolism had occurred as evidenced by reversed-phase and chiral chromatographic separations which revealed the ability of these cells to produce enantiomerically pure (-)-matairesinol. Administrations of [1-¹³C], [2-¹³C ] and [3-¹³C ] specifically labeled phenylalanines to the P. taeda suspension cultures in medium containing NAA allowed the determination of lignin bonding patterns in situ by solid-state ¹³C NMR spectroscopy of the resulting ¹³C enriched cells. Aqueous and organic solvent extractions and protease treatment yielded ¹³C enriched cell walls for solid-state ¹³C NMR spectroscopic analyses of the cell wall bound lignin component. Subsequently, an isolated lignin derivative from these cell walls was analyzed by solution-state ¹³C NMR spectroscopy and verified the assignments made in the solid-state. Accordingly, the above experiments represent the first demonstration of lignin bonding patterns in situ in a Pinus species as well as a suspension culture. This culture system possesses great potential as a model to thoroughly study the early stages of lignification.
Chemical modification of shaped hydrogels in non-aqueous medium
(United States Patent and Trademark Office, 1996-06-25)
A method is described for the chemical modification of pre-shaped hydrogels in non-aqueous medium. The conditions permit the reaction of highly expanded, porous hydrogel particles, such as spherical beads, using pseudo homogeneous reaction conditions in the absence of water. The method involves a three step procedure in which the porous gels are solvent exchanged int a water-free solvent (step 1) with minimal change in gel dimension and porosity; followed by reaction under non-aqueous condition (step 2); and followed by solvent exchange into water (step 3). Many different types of reactions requiring non-aqueous conditions may be carried out using these conditions. The method has particularly been demonstrated for crosslinking fluorinating beads, and for esterifying beads in a reaction involving multifunctional free carboxylic acids in the presence of dicyclohexylcarbodiimide (DCC).
Chitin-based coatings
(United States Patent and Trademark Office, 1999-05-04)
A chitosan starting material is combined with a dilute organic acid to produce a chitosonium ion complex. The chitosonium ion complex is then cast, sprayed, extruded, or otherwise processed to produce filaments, coatings, fibers, or the like. Heat is then used to convert the chitosonium ion complex into a N-(C.sub.1-30)acyl glucose amine polymer.
Clean Fractionation of Biomass - Steam Explosion and Extraction
Ibrahim, Mazlan (Virginia Tech, 1998-02-24)
The fractionation of two biomass resources, red oak (Quercus rubra) chips and oil palm (Elaeis guineensis) trunk solids, into constitutive chemical components, cellulose, hemicelluloses (called "other carbohydrates") and non-carbohydrates (includes lignin, tannins, etc.), was studied quantitatively in terms of relative cleanness. Red oak chips were steam exploded using a batch reactor at five different treatment severities, Ro 5,000, 10,000, 15,000, 20,000 and 35,000. Steam exploded fibers (SEF) of each severity were extracted with water and alkali. Mass fractionation and summative analysis data of all solid biomass fractions were determined. These data were interpreted in term of a unifying clean fractionation concept designed to evaluate the effectiveness of the fractionation processes. Within a series of severities applied to a single biomass resource, the quantitative clean fractionation can be used to choose an optimum severity for the isolation of any particular component fraction. The red oak results revealed that 25 % (on average) of biomass solids were lost during steam explosion. Cellulose remained almost unaffected (retained in fibers form) by water and alkali extraction. About 35-55 % of the hemicelluloses can be recovered in the water extracted liquor fraction (WEL). The remaining non-cellulosic carbohydrates were lost during steam explosion, especially at high severity. At Ro 10,000 and above, alkali extracted fibers (AEF) consists almost entirely of cellulose and non-carbohydrates. The majority of the non-carbohydrates component (> 50 %) can be isolated by alkali extraction. The non-carbohydrate component harvested increased with severity to 67% at Ro 35,000.
Comparative Analysis of Inactivated Wood Surfaces
Sernek, Milan (Virginia Tech, 2002-04-24)
A wood surface, which is exposed to a high temperature condition, can experience inactivation. Surface inactivation results in reduced ability of an adhesive to properly wet, flow, penetrate, and cure. Thus, an inactivated wood surface does not bond well with adhesives. The changes in surface chemistry, wettability, and adhesion of inactivated wood surfaces, including heartwood of yellow-poplar (Liriodendron tulipifera) and southern pine (Pinus taeda), were studied. Wood samples were dried from the green moisture content condition in a convection oven at five different temperature levels ranging from 50 to 200 °C. The comparative characterization of the surface was done by X-ray photoelectron spectroscopy (XPS), sessile drop wettability, and fracture testing of adhesive bonds. The oxygen to carbon ratio (O/C) decreased and the C1/C2 ratio increased with drying temperature. The C1 component is related to carbon-carbon or carbon-hydrogen bonds, and the C2 component represents single carbon-oxygen bond. A low O/C ratio and a high C1/C2 ratio reflected a high concentration of non-polar wood components (extractives/VOCs) on the wood surface, which modified the wood surface from hydrophilic to more hydrophobic. Wettability was directly related to the O/C ratio and inversely related to the C1/C2 ratio. Contact angle decreased with time and increased with the temperature of exposure. Southern pine had a lower wettability than yellow-poplar, which was due to a greater concentration of non-polar hydrocarbon-type extractives and heat-generated volatiles on the surface. Solvent extraction prior to drying did not improved wettability, whereas, extraction after drying improved wettability. A contribution of extractives migration and VOCs generation played a significant role in the heat-induced inactivation process of southern pine. The maximum strain energy release rate (Gmax) showed that surface inactivation was insignificant for yellow-poplar when exposed to drying temperatures < 187°C. The southern pine was most susceptible to inactivation at drying temperatures > 156°C, particularly when bonded with phenol-formaldehyde (PF) adhesive. Chemical treatments improved the wettability of inactivated wood surfaces, but an improvement in adhesion was not evident for specimens bonded with polyvinyl-acetate (PVA) adhesive. NaOH surface treatment was most effective for improving adhesion of the PF adhesive bond.
Crosslinked hydrogel beads from chitosan
(United States Patent and Trademark Office, 1998-06-23)
A chitosan support material is made with crosslinking and installation of a spacer arm between the chitosan matrix and an epoxy terminal group at the distal end of the spacer arm. Among other things, the installed spacer arm endows the crosslinked chitosan beads with enhanced binding specificity during chromatographic separations.
Cure of aqueous phenol-formaldehyde resin at elevated water vapor pressures
Ballerini, Aldo A. (Virginia Tech, 1994-11-19)
The intent of this research was to enhance our knowledge of aqueous phenolformaldehyde resin cure as it is affected by the elevated water vapor pressures that occur during hot-pressing of a wood-based composite. Microdielectric spectroscopy (DEA) was used to monitor the cure reaction, and thermomechanical analysis (TMA), swelling tests and scanning electron microscopy (SEM) techniques were used to characterize the final resin-network. Microdielectric results showed that as the water vapor pressure of the sy stem increases the time to gelation increases. It was also found that the injection of saturated water vapor sharply decreased the gelation time when compared to the other water vapor environmental conditions. In addition, it was found that the higher the water vapor pressure the lower the residual ion viscosity. Thermomechanical analysis and swelling test experiments showed that as the water vapor pressure increases the glass transition temperature and the cross-link density of the cured resin-network decreases. Considerable differences in the morphology of the network were found using SEM. Thus, it can be established that during the curing process under elevated water vapor pressures of a liquid phenol-formaldehyde adhesive some water is trapped into the resin network and it is acting as a plasticizer. A theoretical approach to model the cure kinetics of phenol-formaldehyde has been developed. The model is based on the occurrence of two simultaneous processes (condensation polymerization and evaporation of water) and on the concentration dependency of the activation energy of polymerization.
Design of anion exchange cellulose hydrogel for large proteins
Kumar, Guneet (Virginia Tech, 1994-03-05)
In our previous studies, uncross-linked large diameter cellulose beads were optimized for solids content, bead size, pressure-flow limits, molecular accessibility and performance as an immunosorbent. Here, anion exchange (DEAE) cellulose beads were derivatized by two different procedures (defined as A and B) and the changes in bead morphology were correlated with transport and sorption kinetics. The kinetic characteristics clearly defined a minimum of two different types of protein binding site architecture. DEAE cellulose beads exhibited molecular exclusion of BSA near the edge of the bead in contrast to greater permeability seen in underivatized beads. Thus, accessible BSA binding sites are present only on the surface of the derivatized beads. DEAE cellulose beads derivatized by procedure B gave higher density of DEAE ligand as compared to beads derivatized by procedure A, as well as higher static and dynamic capacity for BSA. Even though DEAE cellulose beads (DP 2070, 450 μm diameter derivatized by procedure B) have lower small ion capacity than DEAE cross-linked agarose beads, as well as 1/4 the surface area, they exhibit equivalent binding capacity for BSA per volume of support. Thus, DEAE cellulose beads possess more sites per surface area as well as have lower ligand density per BSA site. Furthermore, BSA adsorption sites on DEAE cellulose beads derivatized by procedure B exhibit slow binding kinetics as compared to those derivatized by procedure A and also compared to DEAE crosslinked agarose beads. Thus, the rate limiting step for the adsorption of BSA on DEAE cellulose beads was not diffusion as suggested by the large diameter of the bead. Feasibility studies were performed for process scale applications to fixed and expanded bed anion exchange purification. The large diameter DEAE cellulose beads of this study maybe useful for process scale anion exchange as evident from purification of immunoglobulins from hybridoma cell culture in fixed bed. The balance of large diameter and density of these DEAE cellulose beads enable stable expanded bed purification of proteins such as recombinant human protein C from transgenic porcine whey.
Development of sorption technology for the cleanup of pesticide contaminated wastewater
Willems, Hans P. L. (Virginia Tech, 1994)
The use of pesticides in agricultural production has led to the contamination of surface and groundwater. There is a need for simple, on site wastewater cleanup procedures to minimize pollution caused by spills and improper disposal of pesticide wastes by pesticide applicators and farmers. Sorption technology may prove a viable alternative to biological wastewater treatment. Properties of the ideal sorbent are (i) a high capacity for the contaminant, (iii) inexpensive and/or regenerable, and (ili) easy to dispose of after use. Our objective was to evaluate Filtrasorb 400 (activated carbon), Ambersorb adsorbents, and thiol derivatized cellulose beads for pesticide adsorption. Also, the use of solid state fermentation as a means of final disposal of pesticide sorbed onto a lignocellulosic matrix was investigated. Adsorptive capacities of Ambersorb adsorbent 572 for dicamba as Banvel 4L and metolachlor as Dual 8E under flow through conditions were three times higher than adsorptive capacities of Filtrasorb 400. Better performance of Ambersorb adsorbents under flow through conditions was likely the result of faster mass transfer kinetics caused by a more favorable pore size distribution in Ambersorb adsorbents. Ambersorb adsorbents are easily regenerable, with a slight loss of adsorptive capacity, using methanol. Thiol derivatized cellulose beads were synthesized using a novel method. Carbonyldiimidazole activated cellulose beads were reacted with aminoethanethiol to yield thiol contents of up to 160 μmoles/mL beads. Sorption of metolachlor by ethanethiol-cellulose beads was primarily the result of chemisorption, although some physisorption may occur. Chemisorption of metolachlor by ethanethiol-cellulose beads is the result of a nucleophilic substitution reaction, immobilizing metolachlor. Chemisorption increased at elevated temperatures and pH. Sorptive capacity of ethanethiol-cellulose beads for metolachlor in batch studies was similar to Ambersorb adsorbent 572. Ethanethiol-cellulose beads may prove a useful sorbent for contaminants containing electrophilic centers, such as atrazine, simazine, alachlor, and metolachlor. Solid state fermentation of carbofuran in a peat matrix showed that a large amount of carbofuran residues became incorporated into organic matter. The formation of carbofuran-7-phenol was necessary for incorporation to occur. Carbofuran-7-phenol likely was incorporated through peroxidase catalyzed oxidative coupling reactions. Solid state fermentation of contaminants that can undergo oxidative coupling, may prove an effective detoxification method.
Evaluation of ruminal escape potential of crab meal and other protein supplements and influence of steam explosion of ruminal degradability of crab meal
Viswanathan, T. V. (Virginia Tech, 1995)
Four experiments were conducted, three to study the value of crab meal and other protein supplements, and the other to explore the potential of steam explosion technique to improve the nutritive value of crab meal. In Expt. 1, 48 Angus x Hereford and Angus x Simmental steers (avg. BW, 223 kg) were used in a 126-d growth study. Diets were formulated to contain 10.5% CP and 63% TDN, DM basis. In each diet, one third of the N was supplied by the protein supplement. Steers were randomly allotted to the following six supplements: 1) soybean meal (SBM); 2) supplement based on industrial byproducts of both plant and animal origin (IPA); 3) experimental supplement based on byproducts of animal origin (ESA); 4) hydrolyzed supplement No. 3 (HESA); 5) commercial supplement (Pro-Lak®) based on animal protein (CS) and 6) crab meal (CM). There were no significant positive responses in performance and feed efficiency for any of the protein supplemented groups compared to SBM. There was a trend for a positive response in gain to feed for steers fed CS and IPA. Lower weight gain and gain:feed were recorded for the steers fed HESA supplement. Steers fed CM diet had numerically higher growth and gain:feed than those fed SBM. In Expt. 2, two metabolism trials were conducted, each with 24 wether lambs (avg. BW, 25 kg). In addition to the six diets that were used for the growth trial, two other diets were used, a negative control (NC) with no supplemental N, and a diet supplemented with urea (U). The supplements supplied one third of the total dietary N. There were no differences in DM and OM digestibilities among the lambs fed the different protein supplements. Lower (P < .05) apparent absorption of N was recorded for the lambs fed the HESA and NC diets. There were no differences in ruminal fluid pH among the sheep fed different protein supplements. Sheep fed CM tended to have higher total VFA compared to other supplements. Highest (P < .05) ruminal NH₃ N and blood urea N were observed in lambs fed the U diet. In Expt. 3, the ruminal degradability of DM and CP of crab meal and other protein supplements were estimated in situ, in a ruminally cannulated steer. The highest DM degradability was for SBM. The ruminal escape of protem was lowest (P < .05) for SBM (23.2%) and the highest (P < .05) for the ESA supplement (79.8%). The respective values for IPA, HESA, CS and CM were, 60.6, 67.3, 69.8, and 48.4%. The IVDMD of feather meal and blood meal combinations (ESA and HESA) were lowest (P < .05). The IVDMD of crab meal was 67%. In Expt. 4, the potential of steam explosion technique to enhance the nutritive value of crab meal was explored. Crab meal was steam exploded in a batch steam explosion reactor at two levels of severities. Steam explosion decreased (P < .05) N content of crab meal by 20%, and did not improve DM degradability nor increase escape of CP. A 60% increase in chitin degradability, from 21.5 to 34.2% was observed for steam exploded CM. Steam explosion improved IVDMD of CM from 65.9% to 75.2%. These studies illustrated that substituting other protein supplements used in this study for SBM did not elicit a significant positive response in steer performance. Crab meal is comparable to SBM or other commercial products as a protein supplement for steers. Steam explosion does not seem to be a promising processing method for improving utilization of crab waste for ruminants.
Flexural behavior of a glass fiber reinforced wood fiber composite
Smulski, Stephen John (Virginia Polytechnic Institute and State University, 1985)
The static and dynamic flexural properties of a wood fiber matrix internally reinforced with continuous glass fibers were investigated. When modelled as a sandwich composite, the static flexural modulus of elasticity (MOE) of glass fiber reinforced hardboard could be successfully predicted from the static flexural MOE of the wood fiber matrix, and the tensile MOE and effective volume fraction of the glass fiber reinforcement. Under the same assumption, the composite modulus of rupture (MOR) is a function of the reinforcement tensile MOE and effective volume fraction, and the matrix stress at failure. The composite MOR was predicted on this basis with limited success. The static flexural modulus of elasticity, dynamic modulus of elasticity, and modulus of rupture of glass fiber reinforced hardboard increased with increasing effective reinforcement volume fraction. The logarithmic decrement of the composite decreased with increasing effective reinforcement volume fraction. Excellent linear correlation found among flexural properties determined in destructive static tests and nondestructive dynamic tests demonstrated the usefulness of dynamic test methods for flexural property evaluation. The short-term flexural creep behavior of glass fiber reinforced hardboard was accurately described by a 4-element linear viscoelastic model. Excellent agreement existed between predicted and observed creep deflections based on nonlinear regression estimates of model parameters.

Browsing by Author "Glasser, Wolfgang G."

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