Chemical Differences Between the Wood Extracts of Jack Pine (Pinus Banksiana), Black Spruce (Picea Mariana) and Balsam Fir (Abies Balsamea) from Eastern Canada

Abstract

Differences in the chemical composition of the wood of balsam fir (Abies balsamea (L.), jack pine (Pinus banksiana Lamb.) and black spruce (Picea mariana (Mill.)) were determined by GC analysis of their hexane extracts. Certain constituents such as juvabione, (E)-α-atlantone and α-cadinene were shown to be present only in the heartwood of balsam fir. Analysis of the sapwood of the three species also revealed the presence of certain constituents such as juvabione, dehydrojuvabione and (E)- α-atlantone, all found only in balsam fir and an unidentified compound found only in jack pine. The chromatograms of the hexane extracts of both sapwood and heartwood showed characteristic patterns for each of the three species of conifers.     

The Improvement of Bond Strength Properties and Surface Characteristics of Resinous Woods

Apitong (Dipterocarpus spp.) and Caribbean pine (Pinus caribaea Morelet) contain high amounts of extractives that contribute to poor bonding. To reduce, if not to eliminate, the effects of these extraneous substances, surfaces of small wood blocks were Soxhlet-extracted for 8 hours by different solvents. Wettability of the wood surfaces was then measured by droplet and dynamic methods using water and dilute NaOH as liquids. Tensile shear strengths of extracted wood bonded with aqueous vinyl polymer isocyanate (API), resorcinol formaldehyde (RF) and polyvinyl acetate (PVAc) resin adhesives were also measured. Results revealed that although Caribbean pine had much higher resin content than Apitong, the former had better wettability than the latter. Solvent extraction of the adherend with either hexane or ethanol-benzene (1:2) for 8 hours was not enough to improve its wettability but enough to improve its gluability. However, successive extraction with hexane, methanol and ethanol benzene rendered the wood satisfactorily wettable. Generally, a direct relationship between wettability and bond strength could not be observed. In a separate experiment to improve bonding strengths, test specimens were either overheated or autoclaved for 4 minutes at 125°C during the pressing period. Autoclave treatment was found to be useful in increasing the bond strengths of API, RF, PVAc and urea formaldehyde (UF)-bonded Apitong and Caribbean pine.     

Effects of boron compounds on the bonding strength of phenol-formaldehyde and melamine-formaldehyde adhesives to impregnated wood materials

Wood materials are increasingly being used in the construction of structural beams, sports equipment, etc. This study was carried out to determine the bonding strength of phenol-formaldehyde (PF) and melamine-formaldehyde (MF) adhesives to impregnated wood materials. For this purpose, brutia pine (Pinus brutia Ten) and elm (Ulmus compestris L.) woods were impregnated with borax (Bx), boric acid (Ba), Bx + Ba (wt:wt 50:50%), di-ammonium phosphate (D), [D + (Bx + Ba)]/(50 + (25 + 25%), w/w) and Tanalith-C 3310 (T-C 3310) using the vacuum method according to ASTM-D 1413-76. The effects of wood species, impregnating material and type of adhesive on the bonding strength were determined. The highest shear strength (11.09 N/mm²) was obtained from elm wood control (i.e., without any impregnating materials) samples with MF; thus, the impregnation process negatively affected the adhesive bonding strength. Impregnating materials, especially those containing oily or similar solutions such as T-C 3310, are not advised for wood elements which are subjected to shear.     

Effect of Water Stress and Fungal Inoculation on Monoterpene Emission from an Historical and a New Pine Host of the Mountain Pine Beetle

The mountain pine beetle (Dendroctonus ponderosae, MPB) has killed millions of lodgepole pine (Pinus contorta) trees in Western Canada, and recent range expansion has resulted in attack of jack pine (Pinus banksiana) in Alberta. Establishment of MPB in the Boreal forest will require use of jack pine under a suite of environmental conditions different from those it typically encounters in its native range. Lodgepole and jack pine seedlings were grown under controlled environment conditions and subjected to either water deficit or well watered conditions and inoculated with Grosmannia clavigera, a MPB fungal associate. Soil water content, photosynthesis, stomatal conductance, and emission of volatile organic compounds (VOCs) were monitored over the duration of the six-week study. Monoterpene content of bark and needle tissue was measured at the end of the experiment. β-Phellandrene, the major monoterpene in lodgepole pine, was almost completely lacking in the volatile emission profile of jack pine. The major compound in jack pine was α-pinene. The emission of both compounds was positively correlated with stomatal conductance. 3-Carene was emitted at a high concentration from jack pine seedlings, which is in contrast to monoterpene profiles of jack pine from more southern and eastern parts of its range. Fungal inoculation caused a significant increase in total monoterpene emission in water deficit lodgepole pine seedlings right after its application. By 4 weeks into the experiment, water deficit seedlings of both species released significantly lower levels of total monoterpenes than well watered seedlings. Needle tissue contained lower total monoterpene content than bark. Generally, monoterpene tissue content increased over time independent from any treatment. The results suggest that monoterpenes that play a role in pine-MPB interactions differ between lodgepole and jack pine, and also that they are affected by water availability.     

Shear strength and water resistance of modified soy protein adhesives

Soy protein polymers recently have been considered as alternatives to petroleum polymers to ease environmental pollution. The use of soy proteins as adhesives for plywood has been limited because of their low water resistance. The objective of this research was to test the water resistance of adhesives containing modified soy proteins in walnut, maple, poplar, and pine plywood applications. Gluing strength and water resistance of wood were tested by using two ASTM standard methods. Glues with modified soy proteins had stronger bond strength than those containing unmodified soy proteins. Plywood made with glue containing urea-modified proteins had higher water resistance than those bonded with glues containing alkali-modified and heat-treated proteins. After three 48-h cycles of water-soaking, followed by 48 h of air-drying, no delamination was observed for either walnut or pine specimens glued with the urea-modified soy protein adhesives. Gluing strength for wood species with smooth and oriented surface structure was lower than for those with rough, randomly oriented, surface structures. Wood species with greater expansion of dimensions during water-soaking had a higher delamination rate than those showing less expansion.     

Letter

¹⁵N variable contact time (VCT) cross polarization magic angle spinning (CPMAS) NMR experiments were employed to investigate the reaction products formed in wood composites bonded with ¹⁵N-enriched polymeric diphenylmethane diisocyanate (PMDI)-based adhesives. Two wood species were studied. Aspen (Populus tremuloides) and Southern Pine (Pinus sylvestris). The influence of temperature and wood moisture content on the distribution of PMDI-derived species are presented and discussed.     

The unusual occurrence of 14-methylhexadecanoic acid in pinaceae seed oils among plants

14-Methylhexadecanoic (14-MHD) acid has been identified in a sample of pine seed oil (Pinus contorta) by gas-liquid chromatography-mass spectrometry of its picolinyl ester derivative: Its identification (through its equivalent chain length) and its distribution in four conifer families have been checked. It occurred only in Pinaceae, where it was found in 72 species belonging to the genera Pinus, Abies, Cedrus, Tsuga, Pseudotsuga, Larix, and Picea, in the range 0.02–1.15%. 14-MHD acid could not be detected in the lipids of Taxaceae (Taxus baccata), Cupressaceae (Juniperus communis), or Taxodiaceae (Sciadopytis verticillata), even after a 10-fold concentration of the saturated acid fraction isolated by argentation thinlayer chromatography. It is concluded that Pinaceae, along with Ginkgo biloba seed lipids, are major exceptions in the plant kingdom with regard to 14-MHD acid, which otherwise occurs almost exclusively in lipids of animals and microorganisms. The biosynthesis and metabolic role of 14-MHD acid, which other-wise also occur in wood and leaf lipids, remain unknown.     

Analysis of Among-Species Variability in Wood Fiber Surface Using DRIFTS and XPS: Effects on Esterification Efficiency

Abstract

Variability in the chemical composition of surface properties of various wood fibers (eastern white cedar, jack pine, black spruce, and bark) was investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and X-ray photoelectron spectroscopy (XPS). Both DRIFTS and XPS showed high variability in fiber surface composition between species and between fiber types (sapwood, heartwood, and bark). Fiber surface was modified by esterification reaction using a maleic anhydride polyethylene (MAPE) treatment. DRIFTS failed to assess surface modification, whereas XPS results showed that MAPE treatment increased the surface hydrocarbon concentration of jack pine wood fiber, indicated by a decrease in oxygen–carbon ratio and an increase in relative intensity of the C1 component in the C1s signal. Lignin concentration variability on the fiber surface was determined as the major factor that prevents esterification from taking place.     

Detection of Pinosylvins in Solid Wood of Scots Pine Using Fourier Transform Raman and Infrared Spectroscopy

Abstract

Diffuse reflectance Fourier transform infrared (DRIFT) and near infrared (NIR) FT-Raman spectroscopy were used to detect pinosylvins in the wood of Pinus sylvestris L. trees. NIR FT-Raman spectroscopy offered the possibility of revealing pinosylvins simply by visual inspection of Raman spectra whereas DRIFT spectra needed a more complicated evaluation. Pinosylvin and resin acids from Scots pine were examined as to the possibility of their being the cause of observed spectral differences between sapwood and heartwood. Since pinosylvins are important compounds for the decay resistance of Scots pine wood, the detection of pinosylvins with Raman spectroscopy might be used to assess durability of wood products.     

Heat Treatment Effect on Lignin and Carbohydrates in Corsican Pine Earlywood and Latewood Studied by PY–GC–MS Technique

Lignin-derived degradation products from non-treated (NT) and heat-treated (T) Corsican pine (Pinus nigra subsp. laricio) obtained by pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) were investigated, whereby the earlywood (EW) and latewood (LW) parts of the annual ring were considered separately. The data evaluation was done by principal component analysis (PCA) and the Kruskal–Wallis test. There are no differences in the pyrolysis products composition between EW and LW, but NT and T samples were discernible by PCA applied to Py–GC–MS data. Less phenols with longer chains (4-vinylguaiacol, and trans-isoeugenol) than those with shorter chains (guaiacol, 4-methylguaiacol) and an increase of anhydrosugar (AHS) were found among the pyrolysis products after heat treatment. These signs for autocondensation and side chain cleavages in the lignin during heat treatment were more evident in the EW than in the LW and for the crystallization of cellulose. A slight decrease of the carbohydrate/lignin ratio (C/L) after heat treatment indicates a greater degradation of carbohydrates compared to lignin. The relation of pyrolysis products of lignin and mechanical properties of wood was evaluated by regression analysis. An inverse correlation between short-chain phenols and MOE and a direct correlation between long-chain phenols and compression strength was found in case of NT wood, while a weak positive correlation could be observed between short-chain phenols and the density in T wood.     

The effect on shear strength of different surfacing techniques in Oriental beech (Fagus orientalis Lipsky) and Scotch pine (Pinus sylvestris L.) bonded joints

The selection of the most appropriate surfacing technique is influential in the success of bonding, painting and varnishing processes. The objective of the study was to determine which surfacing technique was the most appropriate when applied as the final process in the production of structural wood members, which were subjected to shearing. The study also includes the effect on shear strength of the variables, such as type of wood, plane of cut, type of adhesive and pressing pressure, as they are directly related to the main objective of the study. In view of this objective, the changes in shear strength on radial and tangential cut surfaces of Oriental beech (Fagus orientalis Lipsky) and Scotch pine (Pinus sylvestris L.) woods having different roughness values as a result of sawing with a circular ripsaw, planing and sanding, and bonded with polyurethane (PU) and poly(vinyl acetate) (PVAc) adhesives at 3, 6 and 9 MPa pressure, were studied. The 936 specimens prepared with the objective of determining the effects of variables on bond performance were subjected to a shear test in a universal test equipment in accordance with the ASTM D 905-98 standard. The highest shear strength (13.85 N/mm²) was obtained for the Oriental beech specimens cut from their tangential surfaces with a circular ripsaw, which were glued with PVAc adhesive by applying a pressure of 9 MPa. The lowest value (4.22 N/mm²) was obtained in the specimens planed from their tangential surfaces, which were glued with PU adhesive by applying a pressure of 3 MPa. The specimens obtained from Oriental beech wood showed a higher shear strength compared to the specimens obtained from Scotch pine. In general, in both species of wood, the specimens glued with PVAc adhesive, both on the tangential surfaces and on the radial surfaces, produced higher shear strengths compared to the specimens glued with PU adhesive.     

Magnetic Resonance Imaging of Water Distribution in Welded Woods

This study was performed for a better understanding of water effect on welded wood and improving its water resistance. In this article, we have also attempted to demonstrate the feasibility of using Magnetic Resonance Imaging technology to study water movement in welded woods. Water distribution in welded woods of Scots pine (Pinus sylvestris) and beech (Fagus sylvatica) was investigated by Magnetic Resonance Imaging. Axial specimens were cut from beech and sapwood of Scots pine in longitudinal direction of wood grain. Two pieces of each wood species were welded together by a linear vibration machine. Sub-samples measuring 30 mm × 20 mm × 100 mm were cut from the welded specimens for Magnetic Resonance Imaging. The results showed that weldline of Scots pine was more resistant to water than weldline of beech. Pine joint was still holding after 40 h immersion in water, while a rapid wetting of the beech joint resulted in breakage of the joint in even less than an hour. This preliminary study also showed that MRI is a powerful tool to measure water distribution in welded woods and highlighted the potential of this technique to enhance understanding of wood welding.     

Evaluation of dimensional stability,weathering and decay resistance of modified pine wood by in-situ polymerization of styrene

Abstract

In this study, polystyrene modified Scots pine (Pinus sylvestris L.) wood was investigated upon artificial weathering, decay resistance, dimensional stability and water uptake properties. Polystyrene modification was carried out on pretreated wood by immersion of wood into styrene monomer and further polymerization. The resistance of modified wood against cycles of UV and water exposures was examined by artificial weathering test for 672?hours, and decay resistance was evaluated by attacks of Coniophora puteana and Trametes versicolor on the samples. During the artificial weathering, color and surface roughness of the samples, and macroscopic changes were determined periodically. Changes in the surface chemistry and morphology of the weathered samples were investigated by ATR-FTIR and SEM, respectively. It was proven that polystyrene effectively protected pine samples from both fungi even after leaching procedure, but it was more effective in preventing C. puteana attacks than T. versicolor attacks. As a result of artificial weathering, the surface of all samples was darkened. However, changes in color and roughness as well as crack formations of the modified sample surfaces were found less than those of the untreated samples. Polystyrene also provided considerable improvement on dimensional stability, as well as water repellence of wood.     

Structure–property relationships in one‐component polyurethane adhesives for wood: Sensitivity to low moisture content

The causes of strength loss of wood joints and their consequent delamination from one‐component polyurethane adhesives used for bonding structural wood when used at a low moisture content was investigated by testing wood joint strength and elongation at rupture at different wood moisture contents and by ¹³C‐NMR spectroscopy and scanning electron microscopy of the hardened bond line. The combination of the relative proportion of the still‐reactive free ? NCO groups on the polyurethane, of the wise choice of degree of polymerization of the resin, and of a slower rate of reaction were the three parameters found to be important in overcoming the problem of poor or no bonding of wood at low to very low moisture contents from one‐component polyurethane adhesives. The results obtained indicated that one‐component polyurethane adhesives that had a combination of a higher proportion of still‐unreacted ? NCO groups, a lower degree of polymerization, and a slower reaction rate were capable of overcoming the problem of the high sensitivity of polyurethane gluing at low to very low wood moisture contents. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4181–4192, 2006     

一种木材粘合剂胶接强度新型试验装置的研制

设计了一种由基础框架、加载液压千斤顶、测力弹簧、读数百分表和试样夹具组成的木材粘合剂胶接强度试验装置。有限元数值分析与通用材料试验机的测试比较结果表明：该装置可满足JIS K6852标准的要求，且具有结构简单、体积小、测量可靠和便捷的特点。     

Monoterpene Emissions from Lodgepole and Jack Pine Bark Inoculated with Mountain Pine Beetle‐Associated Fungi

Abstract

Relative monoterpene levels were analyzed from bark samples of lodgepole pine, jack pine, and their hybrids inoculated with mountain pine beetle (MPB)–associated fungi (Leptographium longiclavatum, Grosmannia clavigera, and Ophiostoma montium). Lodgepole pine showed the largest changes in relative emissions as a result of fungal inoculation. The relative emission of β‐phellandrene increased with fungal inoculation, making it the most abundant monoterpene for inoculated samples. Relative emissions of limonene and α‐pinene decreased in inoculated lodgepole pine. Lodgepole (5.6) and jack (146) pine differed in the ratio of α‐pinene to myrcene; two monoterpenes involved in pheromone synthesis by the MPB. These differences may contribute to the attractiveness of the two species as hosts for MPB; with jack pine potentially less attractive than lodgepole pine. Fungal inoculation reduced α‐pinene:myrcene ratios in lodgepole pine, which suggests one possible mechanism by which the fungi benefit the beetle.     

Evolution of Extractive Composition During Thermal Treatment of Jack Pine

Abstract

The thermal treatment of wood has many benefits such as better dimensional stability and attractive dark color and does not use toxic chemicals. The resistance against biological decay can be improved when wood is not in contact with ground. On the other hand, after thermal transformation, wood becomes more fragile. The changes of the wood properties are related to the modification of the wood composition. During the thermal treatment, the evaporation of the moisture content is not the only event. Volatile extractives are evacuated from the wood, while new products and by-products of different chemical reactions appear. The comparison of the extracts obtained from untreated and treated wood can help to identify thermo-chemical reactions, taking place during the heat treatment. This article presents the analysis by Gas Chromatography–Mass Spectroscopy (GC-MS), High Performance Liquid Chromatography (HPLC), and Thin Layer Chromatography (TLC) of polar and non-polar extracts of untreated and heat-treated North American Jack pine (Pinus banksiana). The study of the impact of maximum heat treatment temperature on the composition of the Jack pine extracts showed that the major part of extractives leaves the wood under 200°C whereas most of the new products appear only above 200°C. While the extractives of the untreated Jack pine are dominated by non-polar components, the thermo-transformation seems to generate mainly polar compounds. However, presence of water vapor increases the portion of polar extractives in wood. Interestingly, an important decrease of concentration of phenolic compounds (such as pinosylvin, pinosylvin monomethyl ether, and pinobanksin) in Jack pine wood was observed between 160–200°C. On the other hand, 4-hydroxy-methylfurfural and vanillin have been identified as compounds generated by the heat treatment above 200°C. The identification of other by-products will be presented in a later paper.     

Effects of bilberry (Vaccinium myrtillus L.) litter on seed germination and early seedling growth of four boreal tree species

Laboratory and greenhouse bioassays were used to test for inhibitory effects of senescent and decomposed leaves and aqueous extract from bilberry (Vaccinium myrtillus L.) against seed germination and seedling growth of aspen (Populus tremula L.), birch (Betula pendula Roth.), Scots pine (Pinus sylvestris L.), and Norway spruce [Picea abies (L.) Karst.]. Aqueous extracts from bilberry leaves were inhibitory to aspen seed germination and seedling growth and also induced root damage and growth abnormalities. Addition of activated carbon removed the inhibitory effects of extracts. Senescent leaves reduced pine and spruce seed germination, but rinsing of seeds reversed this inhibition. Senescent leaves were more inhibitory than decomposed leaf litter, suggesting that the inhibitory compounds in bilberry leaves are relatively soluble and released at early stages during decomposition. Spruce was generally less negatively affected by litter and aqueous extracts than the other tested species. This study indicates that chemical effects of bilberry litter have the potential to inhibit tree seedling recruitment, but these effects were not consistently strong. Phytotoxicity is unlikely to be of critical importance in determining success for spruce seedling establishment.     

Effect of geometry and hybrid adhesive on strength of finger joints of Pinus elliottii subject to humidity and temperature

The optimized bonding of glued finger joints is required for structural and nonstructural applications. The use of nonspecific adhesives, combined with the joint geometry and exposure of joints to humidity and temperature, are factors that can compromise the durability of glued joints. The main objective of this study is the development of cross-linking poly(vinyl acetate) (PVAc) hybrid adhesive to produce nonstructural finger joints of Pinus elliottii with finger lengths of 6.5 and 4.5 mm. The adhesives were produced by emulsion copolymerization of vinyl acetate with n-butyl acrylate with different amounts of N-methylol acrylamide and blended with resorcinol-formaldehyde resin (RF) and aluminum chloride (AlCl₃). The rheological behavior of adhesives was investigated. We found that the joint configuration and the exposition time employed influenced joint strength. The PVAc/RF adhesive showed a thicker bond line and consequent deeper penetration into the pores of the wood as verified by microscopy analysis. Statistically differences in bond strength of the adhesive joints were found with respect to different conditioning times and finger length. The highest values were exhibited by the joints produced with a finger length of 6.5 mm and glued with the hybrid adhesive (AD-4) than that joints produced with a finger length of 4.5 mm.     

Effects of Adding Unsaturated Polyester to the PVAC Adhesive on the Dimensional Stability of Laminated Veneer Lumber

Many properties of wood are affected by changes in moisture content below the fiber saturation point of wood. In this study, the dimensional stability of laminated veneer lumber (LVL), according to TSI EN 4084 and EN 4086, was evaluated. For this purpose Scots pine (Pinus sylvestris L.) and Oriental beech (Fagus orientalis L.) LVL panels were used. Panels of LVL were manufactured from cut veneers, and poly-vinyl acetate (PVAc), unsaturated polyester (uPE) and mixtures of them, as adhesives. Laminated veneer lumber panels with 4 plies and 5 mm in thickness were produced for each group. Depending on the adhesive type, the swelling and water absorption of the samples were measured by determining the weight increase in the two conditions of oven dried and being above the fiber saturation point. The lowest volumetric swelling of the Scots pine was measured as 10.4% bonded with 100% PVAc (control) and the highest volumetric swelling was measured as 13.8% bonded with 90% PVAc and 10% unsaturated polyester. The lowest volumetric swelling of the Oriental beech was measured as 17.2% bonded with 100% PVAc (control) and the highest volumetric swelling was found to be 21.8% bonded with 90% PVAc and 10% unsaturated polyester. Statistical analysis results show that adding unsaturated polyester to the PVAc increased the volumetric swelling and water absorption levels of both the Scots pine and Oriental beech LVL panels.