Spruce, common

Woodflour, a fine sawdust preferably obtained from softwoods such as pine, spruce and poplar, is the most commonly used filler. Somewhat fibrous in nature, it is not only an effective diluent for the resin to reduce exotheim and shrinkage, but it is also cheap and improves the impact strength of the mouldings. There is a good adhesion between phenol-formaldehyde resin and the woodflour and it is possible that some chemical bonding may occur. 

Solid wood material is built up of two major organic polymers (macro molecules) (1) polysaccharides and (2) polyphenylpropane [61,62], The polysaccharides consist of two groups - cellulose and hemicellulose, and make up around 65-75 % of the wood on dry basis. The polyphenylpropanes are more commonly termed lignins and constitute around 18-35 % of the wood on dry basis. In Table 9 we can see that wood fuels consist of extractives, minerals, and nitrogen as well. The chemical composition of wood of Sweden s most commonly wood species [63], the spruce, the pine and the birch are different, see Table 9. 

Allelopathic interactions may occur throughout the life of a stand, but are most commonly observed during reforestation or regeneration. Allelopathy prevents some tree species from regenerating, but most regenerate in spite of it. The allelopathic plants of abandoned fields are not common forest species. In contrast, however, Douglas-fir, jack pine, black and white spruce, wild cherry, and slash and loblolly pine seedlings appear to be inhibited by species common in the forest. In such cases... 

Kimland, B., and Norin, T. (1972). Wood extractives of common spruce, Picea abies (L.) Karst. Sven. Papperstidn. 75,403-409. 

Fig. 4.1.17a-c. Near-infrared spectra, (a) Milled wood and MWL from common wingnut (Pterocarya fraxinifolia), hardwood lignin, (b) Milled wood and MWL from dawn redwood, (Metasequoia glyptostroboides). (c) Acetylated Norway spruce (Picea abies) MWL. (Instrument Technikon Infralyzer 500 courtesy of E. Ignatzek, Bran Luebbe, Hamburg)... 

The gluing experiments were done with commercially available starch, proteins (casein, glutin) and tannins of mimosa Acacia spp.), Pinus radiatay and quebracho (Schinopsis spp.) and with tannins extracted from the bark of spruce (Picea abies) and common pine (Pinus sylvestris). The extractions were carried out with water or organic solvents under alkali and/or sulphite conditions on a laboratory scale aiming at optimization of yield and polyphenolic extract content. After extraction, the solutions were concentrated under reduced pressure and freeze dried. One pine bark extract was modified with phenol. A summary of the tannin extracts and their properties is given in Table I. 

Soil samples were collected from the Gardsjon catchment, located at 58° 04 N and 12° 03 E on the west coast of Sweden. The area is covered by coniferous forest with Norway spruce (Picea abies (L.) Karst), which dominate the landscape. The area is glacial till, silt loam soil that is fairly thin. The soil is classified as a spodosol haplorthod, common in Sweden (Nilsson, 1988). A detailed description of the geology, soils, and vegetation of the Gardsjon catchment is given by Olsson et al. (1985). 

There are two plans of branching in trees. When the trunk, or main stem, extends vertically upward to the tip, as it does in the junipers, spruces and other conical trees, the type of branching is called excurrent-, when it divides into several more or less equal divisions as in the elm and other spreading trees, it is said to be deliquescent. The deliquescent plan is the more common one among our deciduous trees. 

Spruce woods resemble the soft pines. They grow extensively in North America and Europe . The common varieties are the Norway spruce Picecs exulsd) and the Douglas spruce or fir (pseudofsuga douglasii). The Norway spruce resembles silver fir but the resin ducts arc visible though few in number. 

Extractive exudation is a common feature of larches, pines, and spruces, and is particularly marked in heartwood samples. It can be controlled to some extent by sealing with an aluminium primer. During high temperature drying of resinous samples of radiata pine heartwood some migration of extractives occurs so that resin accumulates either on or near the surface in a way that is deleterious to wood finishing. 

A systematic approach to the chemical structure of humic or fulvic acid could be patterned on the historical approach to the structure of lignin. Like humic acid, the composition of lignin varies with its source. By common agreement, lignin chemists have adopted Norway spruce as a reference source for native or milled wood conifer lignin. Not only were proposed structural studies based on this lignin material itself, but also on its precursors. Many important structural features were gleaned from a study of precursors and their polymerization products. 

Thick Forest ecosystems are found only along the valley s of large rivers, occupying well-drained places of terraces, slopes and low hills, lying at an altitude of 700-750 m. White spruce (Picea canadensis), balsam poplar, aspen, and in some places white birch, are trees common to these Forest ecosystems black spruce, fir and larch are found more rarely. The latter is attracted to swampy areas. On flat, ill-drained surfaces, forest ecosystems are replaced by vast areas of bog mosses and, in relief depressions, sedge-cotton grass bog. 

Polcin and Rapson published a comprehensive series of papers describing diffuse reflectance studies of the chromophores in spruce and hemlock groundwood pulps [89-91], and their response to some common bleaching agents [92,93]. Based on either reflectance spectra or differences in remission function, they concluded that... 

Svensson et al. [100] compared dithionite bleaching of spruce TMP at pH 10 and pH 5, using principal components analysis to reduce reflectance spectra to contributing subspectra. The authors concluded that at pH 5 (the common pH for commercial dithionite bleaching) quinones were the major chromophores bleached. At pH 10, quinones were formed due to alkali darkening. In spite of the higher redox potential of dithionite at pH 10, bleaching was less efficient than at pH 5, and there was no evidence that any chromophores other than quinones were removed. 

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