Moon G. Kim

Wood Enhancement Treatments I. Impregnation of Southern Yellow Pine with Melamine-Formaldehyde and Melamine-Ammeline-Formaldehyde Resins

Abstract Southern yellow pine (SYP) was impregnated with melamine-formaldehyde (MF) or melamine-ammeline-formaldehyde (MAF) resins. The dimensional stability, strength properties, weathering, fire resistance and chemical resistance of the impregnated wood were examined. The wood treated with two commercial MF resins or with a synthesized MAF resin exhibited greatly enhanced dimensional stability, fire resistance and resistance to weathering. The chemical resistance increased moderately.

Examination of Selected synthesis parameters for typical wood adhesive-type urea-formaldehyde resins by 13C NMR spectroscopy. I

Selected synthesis parameters of typical wood adhesive-type urea-formaldehyde (UF) resins were examined using the 13 C NMR spectroscopy. The monomeric hydroxymethylureas and methylene-ether derivatives formed in the initial alkaline reaction polymerize in the subsequent acidic reaction by forming methylene bonds and cleaving some hydroxymethyl groups as formaldehyde. For typical resin syntheses at F/U ratio of 2.10, the resulting UF polymer is found to be a number-averaged pentamer having 3.25 polymer chain branches with about 80% of chain ends bonded to hydroxymethyl groups and the rest being free amide groups. When the second urea is added during the cooling period, about 67% of hydroxymethyl groups cleave from the UF polymeric components and the freed formaldehyde reacts with second urea to form monomeric hydroxymethylureas. This hydroxymethyl group move is suppressed when the second urea is added at low temperatures, suggesting that wood adhesive-type UF resins are composed of monomeric and polymeric UF components having hydroxymethyl functional groups in varying proportions.

Polymer structure of cured alkaline phenol–formaldehyde resol resins with respect to resin synthesis mole ratio and oxidative side reactions

A wood adhesive-type phenol–formaldehyde (PF) resol resin synthesized with a typical formaldehyde to phenol mol ratio of 2.10 was thoroughly cured and studied by the solid-state crosspolarization/magic angle spinning 13C nuclear magnetic resonance (CP/MAS NMR) spectroscopy. The methylene group/phenol mol ratio values found were between 1.35 and 1.46, close to the value of a completely cured PF polymer structure. The amount of formaldehyde emitted during resin curing was very small. Other formaldehyde-derived groups determined from CP/MAS NMR spectra and relatively high levels of oxidation products of formaldehyde determined from water extracts of cured resin raised the total formaldehyde-derived groups/phenol mol ratio value to close to that of the synthesis mol ratio. Technological implications of these findings are discussed.

Effects of Urea Addition to Phenol-Formaldehyde Resin Binders for Oriented Strandboard

ABSTRACT Effects of urea addition to oriented strandboard (OSB) binder phenol-formaldehyde (PF) resol resins were investigated at 0, 10, 18, and 26% urea addition levels. PF resins were synthesized at these urea levels with the resin solids levels and viscosities being kept approximately constant at 50% and 150 − 250 cP, respectively. Analysis results of synthesized resins indicated that the urea additions lowered the free formaldehyde content and increased the degree of polymerization but decreased the curing rates. Evaluation of the laboratory OSBs manufactured using the synthesized resins as binders showed that the internal bond (IB) strength and the water soak properties were decreased gradually as the urea addition level was increased.

Optimization of hot-compressed water pretreatment of bagasse and characterization of extracted hemicelluloses

Developing optimum treatment and separation procedures for hemicellulose components of lignocellulosic biomass could be useful in ethanol fermentation processes and obtaining pure hemicelluloses as biopolymers. Sugarcane bagasse analyses indicate that xylose is the major hemicellulose component constituting 17.7% of dry bagasse weight. In this study the effects of treatment conditions such as time, temperature and pressure on the yields of extracted hemicelluloses were studied. The optimum conditions were achieved at 180 °C for 30 min and 1 MPa pressure, with the yield of xylose reaching to 85% and the concentrations of sugar degradation products such as HMF and furfural remaining minimal at 0.95 and 0.07 g/L, respectively. Further, isolation of hemicelluloses from extracted hemicelluloses solutions was performed using Alfa Laval M20 membrane filtration system in two steps: (1) concentration of high molar mass hemicelluloses by ultrafiltration; and (2) separation of low molar mass hemicelluloses and oligomeric sugars by nanofiltration. The isolated hemicelluloses with the optimum pretreatment conditions were characterized by FT-IR and (13)C NMR techniques, resulting in agreement with typical spectra of xylan-type hemicelluloses.

POLYURETHANE RESINS-TREATED WOOD PALLETS WHICH ARE DECONTAMINABLE OF CHEMICAL WARFARE AGENTS*

Wood pallets manufactured by impregnating and coating wood with selected polyurethane resins performed comparably to steel control pallets in decontamination of major chemical warfare agents before and after being subjected to various rough-handling and strength test procedures. Cost calculations showed that the wood pallets would be competitive with steel pallets. * See Ref. [1].

WOOD MADE DECONTAMINABLE OF CHEMICAL WARFARE AGENTS AFTER SUNLIGHT WEATHERING OR ABRASION

Methods of making wood decontaminable of major chemical warfare agents were investigated using phenol-formaldehyde and polyurethane resins. Selected phenol-formaldehyde resins impregnated in southern yellow pine gave enhanced dimensional stability and fire resistance properties without decreasing strength properties, but the decontaminability for one major chemical warfare agent was inadequate. Selected polyurethane resins impregnated in southern yellow pine gave enhanced dimensional stability and strength properties with only a minor deterioration in fire properties, and southern yellow pine, red oak, and aspen impregnated with these polyurethane resins were adequately decontaminated of all three major chemical warfare agents. A polyurethane resin that performs adequately as a coating material for this purpose was also identified. *See Ref. [1].