Veneer system

In the automated lay-up system, each layer of veneer (with exception of the top surface veneer) passes under an automatic adhesive appHcation system. This may be a spray appHcation, a curtain coater, or an extmder, each of which is designed to apply a uniform adhesive spread on the upper face of each veneer. After all except the top veneer have been spread with adhesive and laid together, the top veneer is added. The me of the veneer—adhesive assembly at this point should be about 8%. 

This is, of course, a very Terra-centric categorization, but so far we only have the unitary example of Earth from which to draw examples. Furfaro et al. (2007) have developed a fuzzy-logic-based scheme that goes more toward the fundamentals of coupled physical/biological planetary systems, but still it takes a restricted view oriented toward Mars- and Earth-like planets. It is entirely possible that Earth has a thin biospheric veneer compared to potentially more massive biospheres on worlds with deep ice-covered oceans such as Europa we just don t know. 

Biblos and Coleman investigated another type of potential structural composite product (53). They made and tested panels consisting of a particleboard core from sawdust and bark and faces of veneer. All material was southern pine, and 9% urea formaldehyde served as binder. Strength tests indicated the composite panels were superior to conventional two-layer floor systems of 1/2-inch plywood plus 5/8-inch particleboard underlayment. 

The veneer dryers of a plywood mill are large chambers equipped with heating elements and fans utilizing automatic conveying systems on which the veneers are transported. Some dryers are located behind the rotary lathe, which allows the cut veneer to be dried in a continuous sheet or ribbon and then clipped dry afterwards. 

The oldest samples that provide direct constraints on the osmium isotopic composition of the upper mantle are rare spinel peridotites contained within the Early Archean Itsaq gneiss complex of southwest Greenland that are interpreted to be —3.81 Ga abyssal peridotites (Friend et al., 2002). The measured and initial compositions determined from low-Re/Os spinel and olivine mineral separates from these peridotites are the most primitive, in the sense of closest to solar-system initial compositions, Os isotopic compositions yet obtained on any terrestrial material (Bennett et al., 2002). This shows that at least some, if not all, of the Early Archean upper mantle was characterized by chondritic Os/ Os isotopic compositions. Osmium isotopic constraints from this time period (—3.8-3.9 Ga) are of particular interest as they provide a rough constraint on the timing of the addition of the late veneer of... 

In designing concrete tanks, it is common practice to carry the reinforced asphalt membrane up the walls and over the tops of the concrete, and to continue the brick lining in the same manner-over the top of the wall. Often the membrane is carried down the outside of the tank, the outside is veneered with brick as well, and the membrane and brick continued onto the surrounding floor. If such a system is properly designed and constructed, the life expectancy of the system will be a long one. This is a closed system, with no discontinuities in membrane, and except for mechanical injury there is no way corrosives can enter the building structure. 

In chemical plants where corrosive, wet conditions are anticipated, walls are protected with membranes and brick veneers in the same manner as floors. Alternatively, a divider wall between two rooms, or one that is to support a roof or other load, may be built entirely of "acid brick" and mortar. A different, more attractive system, is usually followed in food plants such as dairies, often employing glazed tile or block. The latter are laid just as are regular cement block, except that the face joints are left void to a depth of % in. or more, or raked back to that depth before the joints set up. After cure, the surfaces of the joint are cleaned usually with dilute hydrochloric acid, and the joints pointed full with a furan mortar. See Drawing 14 to see how this kind of a wall is mated to an "acid brick" floor and membrane. 

Treatment of solid wood over the years for increased utility included many chemical systems that affected the cell wall and filled the void spaces in the wood. Some of these treatments found commercial applications, while some remain laboratory curiosities. A brief description of the earlier treatments is given for heat-stabilized wood, phenol-formaldehyde-treated veneers, bulking of the cell wall with polyethylene glycol, ozone gas-phase treatment, ammonia liquid- and gas-phase treatment, and p- and y-radiation. Many of these treatments led to commercial products, such as Staybwood, Staypak, Im-preg, and Compreg. This chapter is concerned primarily with wood-polymer composites using vinyl monomers. Generally, wood-polymers imply bulk polymerization of a vinyl-type monomer in the void spaces of solid wood. 

A limited amount of experimentation was made with plywood and laminated panels. These experiments used the same ammonium lignosulfonate/poly(furfuryl alcohol) resin or monomer systems, with H2O2 activation, maleic acid as catalyst, and Douglas-fir veneer. A dry wood failure of 100% was obtained with plywood (83% and 95% wet, after vacuum-pressure soak), with dry shear strength of 1135 psi for parallel laminated panel made with ammonium lignosulfonate-furfuryl alcohol (525 psi wet), and of 1640 psi for the one made using ammonium lignosulfonate/furfuryl alcohol resin (650 psi wet). 

By applying a steady pressure against the bolt the nosebar takes up any slack in the mechanical system due to wear, and guides the knife in relation to the outer surface of the bolt. This helps to ensure a veneer of constant thickness. 

Veneer should be cut from logs as soon as possible after felling. If logs are stored they are best kept fully submerged or in a sprinkler system to prevent decay... 

Platen dryers. Drying systems have been considered that heat the surface of the veneer directly with heated platens (Loehnertz, 1988 Pease, 1980). A single veneer is placed on the lower plate in each daylight of the multiple daylight press and the platens elosed (100-200 kPa pressure on the veneer) so keeping the veneer flat... 

Pease D (1980) Platen veneer drying systems cut shrinkage and energy costs. Forest Industries, 107(1) 29-31... 

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