Anthony H. Conner

United States Department of Agriculture, Washington, Washington, D.C., United States

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Publications (35)55.07 Total impact

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    ABSTRACT: A bioadhesive composition for bonding together adjacent surfaces of wood comprises a microbially-produced fermentation residue containing adherent microbial cells and glycocalyx. This residue finds particular application as a replacement for a significant amount of phenol-formaldehyde (PF) or other conventional adhesive component commonly used in the production of plywood and other wood products.
    Full-text · Article · Jan 2006
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    P J Weimer · AH Conner · L F Lorenz
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    ABSTRACT: Residues from the fermentation of cellulose by the anaerobic bacteria Ruminococcus albus (strain 7) or Ruminococcus flavefaciens (strains FD-1 or B34b) containing residual cellulose, bacterial cells and their associated adhesins, were examined for their ability to serve as components of adhesives for plywood fabrication. The residues contained differing amounts of protein (0.4-4.2% of dry weight), but the ratios of monosaccharides recovered following two-stage treatment of the residue with detergent (pH 7) and TFA were similar for all three strains (0.71 glucose:0.18 xylose:0.08 mannose:0.02 galactose), suggesting similarities in exopolysaccharide composition. Three-ply aspen panels prepared with fermentation residues (FR) displayed better shear strength and wood failure under dry conditions than following a vacuum/pressure/soak/dry treatment, but adhesive properties were inferior to those prepared with conventional phenol-formaldehyde (PF) adhesives. However, panels prepared by incorporating the R. albus 7 FR into PF formulation, at 73% by weight of the total adhesive, exhibited shear strength and wood failure similar to that obtained with PF adhesive alone. Use of residues from fermentations by these bacteria as components of adhesives may add value to biomass fermentations aimed primarily at producing ethanol and other chemical products.
    Full-text · Article · Dec 2003 · Applied Microbiology and Biotechnology
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    Anthony H. Conner · Linda F. Lorenz · Kolby C. Hirth
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    ABSTRACT: 2-Hydroxymethylphenol (2-HMP) and 4-hydroxymethylphenol (4-HMP) were used as model compounds to study the reactions that occur during cure of phenol–formaldehyde (PF) resin to which cure accelerators (ethyl formate, propylene carbonate, -butyrolactone, and triacetin) have been added. The addition of cure accelerators significantly increased the rate of condensation reactions. The cure accelerators were consumed during the reaction, indicating that they do not act as true catalysts. Major dimeric and trimeric reaction products were isolated and their structures determined. The results are consistent with a mechanism in which the hydroxymethyl group of 2-HMP (or 4-HMP) is first transesterified by the cure accelerator. The ester group is then displaced by reaction with the negatively charged ortho or para position of a second molecule (SN2 mechanism) or is converted to a reactive quinone methide intermediate, which subsequently reacts with the negatively charged ortho or para position of a second molecule (quinone methide mechanism). When accelerators were added to the reaction mixture, the self-condensation of 2-HMP was faster than that of 4-HMP. As is well documented in the literature, the exact opposite is true without added accelerators. This result would seem to indicate that the phenolic oxygen helps activate the esterified ortho-hydroxymethyl group. The number and nature of crosslinks in a PF resin cured with added cure accelerator might be different than those in a PF resin cured without an added cure accelerator. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3256–3263, 2002
    Full-text · Article · Dec 2002 · Journal of Applied Polymer Science
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    Tohru Mitsunaga · Anthony H. Conner · Charles G. Hill Jr
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    ABSTRACT: Phenol–formaldehyde resins are important adhesives used by the forest products industry. The phenolic compounds in these resins are derived primarily from petrochemical sources. Alternate sources of phenolic compounds include tannins, lignins, biomass pyrolysis products, and coal gasification products. Because of variations in their chemical structures, the reactivities of these phenolic compounds with formaldehyde vary in quite subtle ways. Previously, it was demonstrated that the reactivity of a number of phenols with formaldehyde in nonaqueous conditions could be correlated with charges calculated for reactive sites on the aromatic ring (Conner, A. H. J Appl Polym Sci 2000, 78, 355–363). We studied the reactivity of a larger number of phenolic compounds with formaldehyde in an aqueous solution using sodium hydroxide as the catalyst. Reaction rates were determined from measurements of the concentrations of the phenolic compounds and formaldehyde as functions of time. The reaction rate constants varied over a wide range (approximately 10−2 to 104 L mol−1 h−1). An estimate of the reactivity per reactive site on the phenolic ring was determined by dividing the rate by the number of reactive sites. Atomic charges for each phenolic compound were calculated by ab initio methods at the RHF/6-31+ G level of theory using the CHelpG method. The charge per reactive site was estimated by summing the charges at all the reactive sites on the phenolic ring and dividing by the number of reactive sites. A strong correlation was observed between the reactivity per reactive site and the average charge per reactive site. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 135–140, 2002
    Full-text · Article · Oct 2002 · Journal of Applied Polymer Science
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    Tohru Mitsunaga · Anthony H. Conner · Charles G. Hill
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    ABSTRACT: The rates (k) of hydroxymethylation of phenol, resorcinol, phloroglucinol, and several methylphenols in diluted 10% dimethylformamide aqueous alkaline solution were calculated based on the consumption of phenols and formaldehyde. Thek values of phloroglucinol and resorcinol relative to that of phenol were about 62000 and 1200 times, respectively. The phenols that have methyl or hydroxyl groups at the C-3 or C-5 position (or both) have larger rate constants than phenols with substituents at other positions. Several kinds of atomic charge of the carbons on the aromatic ring of phenols were calculated using the semiempirical orab initio method. The correlations between the averagek (Ave.k) and average electrostatic charges (Ave.q) at the carbons were fairly good. Highest occupied molecular orbitals (HOMO) were observed. The best correlation between Ave.k and Ave.q was obtained when diphenols and triphenols were assumed to exist in solution as their respective di-anion.
    Full-text · Article · Mar 2002 · Journal of Wood Science
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    Anthony H. Conner · Melissa S. Reeves
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    ABSTRACT: Computational chemistry methods can be used to explore the theoretical chemistry behind reactive sys- tems, to compare the relative chemical reactivity of dif- ferent systems, and, by extension, to predict the reactiv- ity of new systems. Ongoing research has focused on the reactivity of a wide variety of phenolic compounds with formaldehyde using semi-empirical and ab initio computational chemistry methods. This research has been expanded to study theoretical transition states formed on reacting phenol with formaldehyde. Accord- ing to transition state theory, the energy of a transition state is related to the reaction rate. Transition states for reaction of formaldehyde at the ortho- and para-posi- tions of phenol were determined by computational means. These theoretical calculations predict that formaldehyde reacts faster at the para-position of phe- nol than at the ortho-position, in agreement with ex- perimental data.
    Preview · Article · Jan 2001
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    Tohru Mitsunaga · Anthony H. Conner · Charles G. Jr. Hill
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    ABSTRACT: Phenolic resins are important adhesives used by the forest products industry. The phenolic compounds in these resins are derived primarily from petrochemical sources. Alternate sources of phenolic compounds in- clude tannins, lignins, biomass pyrolysis products, and coal gasification products. Because of variations in their chemical structures, the reactivities of these phenolic compounds with formaldehyde vary in quite subtle ways. A method is needed for predicting the reactivity of phenolic compounds with formaldehyde in order to al- low researchers to efficiently choose those compounds that might make the best candidates for new adhesive systems prior to conducting extensive laboratory trials. Computational chemistry has been used to study the relationship between the reactivity of a number of phe- nolic compounds with formaldehyde in an aqueous, al- kaline system, and charges calculated for reactive sites on the aromatic ring of the phenolic compound. Atomic-charges for each phenolic compound were cal- culated by ab initio methods at the RHF/6-31 +G level of theory using the ChelpG method. Reaction rate con- stants were determined from measurements of the con- centrations of the phenolic compounds and formalde- hyde as functions of time. The reaction rate constants varied over a wide range (approx. 10 -2 to 10 4 L mol -1 hr. -1 ). An estimate of the reactivity per reactive site on the phenolic ring was determined by dividing the rate constant by the number of reactive sites. The charge per reactive site was estimated by summing the charges at all the reactive sites on the phenolic ring and dividing by the number of reactive sites. A strong correlation was observed between the reactivity per reactive site and the average charge per reactive site.
    Full-text · Article · Jan 2001
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    Anthony H. Conner
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    ABSTRACT: A method is needed to predict which compounds, from the many alternative phenolic compounds, might be best for making polymeric phenolic systems. Kinetic data for the reaction of a series of phenolic compounds with formaldehyde using a base catalysis are available in the literature. Semiempirical calculations, using RHF/PM3, and ab initio calculations, using RHF/6-31G, RHF/6-31+G, and B3LYP/6-311+G(2d,p), were performed on the series of phenolic compounds to determine their relative reactivities. Atomic charges were determined for the phenolate anions. For each compound, I summed the absolute value of the calculated, negative charges residing on carbon atoms of the phenolic ring at which the HOMO was located and at which no substituent was present to cause steric interference with the reaction. The sum of the charges for each compound was then regressed against the log of the relative reaction rate for that compound. The sum of charges from PM3-based calculations gave poor correlation with reactivity. The sums of charges calculated by the CHelpG and Merz–Kollman/Singh methods at the ab initio levels of theory give excellent correlations with reactivity of the phenolics toward formaldehyde. Based on the calculated charges, estimates of the relative reactivity at each of the reactive sites on each of the phenolic compounds were determined. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 355–363, 2000
    Preview · Article · Oct 2000 · Journal of Applied Polymer Science
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    S Sowunmi · R O Ebewele · O Peters · AH Conner
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    ABSTRACT: Mangrove-bark-tannin adhesives are potential substitutes for phenol–formaldehyde (PF) wood-bonding adhesives which are derived from petroleum, a finite natural resource. However, mangrove-bark-tannin adhesive exhibits poor adhesive properties, including brittleness, poor wet strength, and poor wood penetration. These shortcomings are due to its high reactivity and structural features. To reduce these shortcomings, the structure of the adhesive was modified by subjecting tannin to (a) caustic hydrolysis and (b) consecutive acetic anhydride and caustic hydrolysis. The effectiveness of these hydrolyses was determined by using differential scanning calorimetry (DSC) to monitor the reaction and cure characteristics of hydrolysed and unhydrolysed tannin with formaldehyde. These hydrolyses resulted in lowering both the activation energy and collision frequency of the cure reaction. Consequently, the initial reactivity of tannin towards paraformaldehyde, which was usually very high, was reduced. The resulting longer reaction time enhanced the extent of reaction, as was evident in the increase in heat of reaction of the hydrolysed tannin.© 2000 Society of Chemical Industry
    Preview · Article · Jun 2000 · Polymer International
  • L.F. Lorenz · A.H. Conner · A.W. Christiansen
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    ABSTRACT: Urea-formaldehyde (UF) resins were modified with soy protein, hydrolyzed soy protein, soy flour, or casein, at 1.5 to 50 percent of UF solids, to determine if modifying the resins would reduce formaldehyde emissions. Differential scanning calorimetry was used to determine the reactivity of the modified UF resins compared with unmodified UF resin. The reactivity was reduced as the added protein modifier increased, but up to 30 percent protein modifier could be added to the UF resin before the reactivity was reduced significantly. Formaldehyde emissions from cured UF resins were not decreased as the amount of protein modifier added to the resin was increased.
    No preview · Article · Mar 1999
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    Michael S. Holfinger · § and Anthony H. Conner · Charles G. Hill, Jr
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    ABSTRACT: The effects of temperature, acid concentration, and reactant concentration on the rate of formation of difurfuryldiamines from the reactions of furfurylamine with formaldehyde and acetaldehyde were experimentally investigated. On the basis of the data from these experiments, a semimechanistic reaction model network was proposed and a mathematical model which describes the observed kinetic behavior was derived. Rate constants for the model reactions were found to depend exponentially both on the reciprocal of the absolute temperature and on the acid concentration. The mathematical model predicts concentration versus time profiles for reactants, intermediate, and product for the reaction of furfurylamine and acetaldehyde under the following conditions:  20 °C < temperature < 50 °C, 3 M < nominal acid concentration < 6 M, 1.17 M < [furfurylamine] < 1.2 M, and 0.303 M < [acetaldehyde] < 1.17 M. For the reaction of furfurylamine with formaldehyde the model is applicable for 30 °C < temperature < 50 °C, 3 M < nominal acid concentration < 6 M, [furfurylamine] = 1.17 M, and [formaldehyde] = 0.58 M.
    Full-text · Article · Mar 1997 · Industrial & Engineering Chemistry Research
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    S. Sowunmi · R. O. Ebewele · A. H. Conner · B. H. River
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    ABSTRACT: Mangrove bark tannin adhesives are based on a renewable resource. They are potential substitutes or supplements for phenol–formaldehyde (PF) wood-bonding adhesives which are derived from petroleum, a finite natural resource. However, mangrove tannin adhesives exhibit poor adhesive properties including poor wet strength, brittleness, and poor wood penetration. These problems were addressed by treating tannin extract with acetic anhydride and then sodium hydroxide followed by modification with 20% resole-type PF resin. Significant structural changes occurred after the chemical treatment. Heat of reaction of tannin with formaldehyde was increased while the activation energy was drastically reduced. Premature cure was also reduced. The fortified formulations had good plywood adhesive properties. © 1996 John Wiley & Sons, Inc.
    Preview · Article · Oct 1996 · Journal of Applied Polymer Science
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    David R. Holm · Charles G. Hill · Anthony H. Conner
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    ABSTRACT: The liquid phase hydrogenation reactions of both furfurylamine and 5,5'-ethylidenedifurfurylamine to the corresponding tetrahydrofuran compounds have been investigated over a rhodium on alumina catalyst suspended in a methanol solution. The reactions were studied at temperatures from 42.5 to 80.1 degrees C and hydrogen pressures from 231 to 1380 kPa (33.5 to 200 psi). The effects of the amount of catalyst and the concentrations of both reactants and products on the rates of these reactions were also investigated. Analysis of the data from these investigations using the method of initial rates indicates that the rates of hydrogenation of both furfurylamine and 5,5'-ethylidenedifurfurylamine are consistent with Hougen-Watson-Langmuir-Hinshelwood reaction mechanisms. The overall activation energies for the hydrogenation of furfurylamine and 5,5'-ethylidenedifurfurylamine are 49.4 +/- 2.5 and 63 +/- 4 kJ/mol, respectively.
    Full-text · Article · Oct 1995 · Industrial & Engineering Chemistry Research
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    ABSTRACT: Difurfuryl diamino compounds can be obtained via single-step reactions of furfurylamine with formaldehyde and other aldehydes in 2.5-5.2 M hydrochloric acid at 20-50 degrees C. Yields for the single step reaction (30-50%) are comparable to those for three-step procedures involving protection and deprotection of the amino group.
    Full-text · Article · Mar 1995 · The Journal of Organic Chemistry
  • Michael S. Holfinger · Anthony H. Conner · Charles G. Hill Jr
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    ABSTRACT: A protocol which employs a methyl silicone gum capillary column for gas chromatographic analysis of the products of the acid- catalyzed reaction of furfurylamine with aldehydes is presented, and its efficacy is demonstrated.
    No preview · Article · Aug 1993 · Journal of Chromatography A
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    ABSTRACT: The syntheses of difurfuryl diisocyanates [e.g., ethylidenebis (2,5-furandiylmethylene) diisocyanate (EDFI)] have been reported in the literature. Difurfuryl diisocyanates are structurally similar to diphenylmethane diisocyanate (MDI), which has proven to be an excellent adhesive for bonding wood composites. The MDI regin is synthesized from petroleum-derived chemicals; the EDFI resin is synthesized from biomass-derived chemicals. In this study, the mechanical properties of aspen flakeboards bonded with MDI and EDFI are compared. In general, results show that the strength properties of flakeboards bonded with MDI are only marginally better than those bonded with EDFI. Because EDFI is more viscous than is MDI less than optimum atomization of the EDFI resin during spraying of the flakes is believed to be largely responsible for the differences in strength property values. The dry internal bond strength values of flakeboards bonded with MDI (1.33 MPa; 193 lb/in.2) at 3% resin content are significantly greater than the 0.41 MPa (60 lb/in.2) required by the American National Standards Institute (ANSI/A208.1) for type-2 medium-density particleboard. © 1993 John Wiley & Sons, Inc.†
    Full-text · Article · Jul 1993 · Journal of Applied Polymer Science
  • Chyong-Huey Lin · Anthony H. Conner · Charles G. Hill
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    ABSTRACT: Thirteen prehydrolyzed samples of cellulose, including native, mercerized, and regenerated materials were hydrolyzed in 1% and 1.5% sulfuric acid at 160, 170, and 180°C. Pseudo first-order rate constants and weight average degrees of polymerization were determined for each sample. For all cellulose samples, data from several experiments were used to determine the dependence of the rate of hydrolysis on sulfuric acid concentration. The results obtained in this study indicate that Sharples' end-attack model is consistent with kinetic data for the hydrolysis of cellulose II samples, but is not applicable to the hydrolysis of cellulose I samples. X-ray diffraction analyses indicated that, for native and mercerized cellulose samples, structural changes during dilute acid hydrolysis are not significant. However, data for rayon indicated that such changes may need to be taken into account in analysis of the reaction kinetics.
    No preview · Article · Aug 1992 · Journal of Applied Polymer Science
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    K Kleman-Leyer · E Agosin · A H Conner · T K Kirk
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    ABSTRACT: The kinetics of cotton cellulose depolymerization by the brown rot fungus Postia placenta and the white rot fungus Phanerochaete chrysosporium were investigated with solid-state cultures. The degree of polymerization (DP; the average number of glucosyl residues per cellulose molecule) of cellulose removed from soil-block cultures during degradation by P. placenta was first determined viscosimetrically. Changes in molecular size distribution of cellulose attacked by either fungus were then determined by size exclusion chromatography as the tricarbanilate derivative. The first study with P. placenta revealed two phases of depolymerization: a rapid decrease to a DP of approximately 800 and then a slower decrease to a DP of approximately 250. Almost all depolymerization occurred before weight loss. Determination of the molecular size distribution of cellulose during attack by the brown rot fungus revealed single major peaks centered over progressively lower DPs. Cellulose attacked by P. chrysosporium was continuously consumed and showed a different pattern of change in molecular size distribution than cellulose attacked by P. placenta. At first, a broad peak which shifted at a slightly lower average DP appeared, but as attack progressed the peak narrowed and the average DP increased slightly. From these results, it is apparent that the mechanism of cellulose degradation differs fundamentally between brown and white rot fungi, as represented by the species studied here. We conclude that the brown rot fungus cleaved completely through the amorphous regions of the cellulose microfibrils, whereas the white rot fungus attacked the surfaces of the microfibrils, resulting in a progressive erosion.
    Full-text · Article · May 1992 · Applied and Environmental Microbiology
  • Xiaodun He · Anthony H. Conner · James A. Koutsky
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    ABSTRACT: Epoxy resin adhesives are widely used because of their strength, versatility, and ability to bond a variety of substrates. Furfurylamines represent a potential, new class of epoxy curing agents. Furfuryl amine (FA), tetrahydrofurfuryl amine (THFA), and 5,5′-methylenebis-2-furanmethanamine (DFA) were studied as possible epoxy curing agents. The utility of FA and THFA are limited by their volatility at the temperatures needed to effect cure of diglycidyl-ether of bisphenol A (DGEBA) based epoxy resins. DFA is a very effective epoxy curing agent with the ability to cure DGEBA at rates similar to that of standard epoxy curing agents such as liethylenetriamine.
    No preview · Article · Mar 1992 · Journal of Polymer Science Part A Polymer Chemistry
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    T. Kent Kirk · Rebecca Ibach · Michael D. Mozuch · Anthony H. Conner · L. Highley
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    ABSTRACT: Wood decay fungi of the brown-rot type destroy the strength of wood before significant weight loss occurs. This is due to extensive depolymerization of the cellulose. Evidence indicates that enzymes cannot gain access to the cellulose in wood and that the depolymerizing agent might be oxidative. Our objectives here were to gain information about the nature of the agent by characterizing pure cellulose that had been depolymerized by a brown-rot fungus (BR) and to compare its characteristics with those of cellulose depolymerized by acid (A), by Fenton's reagent (Fe2+ + H2O2) (F), or by periodic acid/bromine/water (P). All four types of depolymerized cellulose exhibited molecular size characteristics indicating that depolymerization was due to cleavages within the noncrystalline regions. Carbonyl contents of the samples were similar, from 1.4 to 1.9 per cellulose molecule. Carboxyl contents were 0.44, 0.00, 0.24, and 7.38 per molecule for samples BR, A, F, and P, respectively; uronic acids were absent except for a trace in sample P. On complete acid hydrolysis the samples gave the expected amounts of glucose, except for sample P, which contained nonglucosyl moieties that did not contain carbonyl or carboxyl groups detected by our analytical procedures. With the glucose in the acid hydrolysates we found glyceric, erythronic, ararbonic, and gluconic acids in samples BR and F, and erythronic acid in sample of P. Our results indicate that the brown-rotted cellulose resembles sample F more than samples A or P.
    Full-text · Article · Aug 1991 · Holzforschung