End-jointing adhesives

Kreibich, R. E., Use of Bark Tannins in End-Joint Adhesives for Wood. Final Report-Phase I to the USDA Small Business Innovation Research Program on grant 86-SBIR-8-0126, R. E. Kreibich, Auburn WA., 1987. 

Plywood requirements—includes wood species used, synthetic repair requirements, veneer grades, veneer layers and thicknesses, panel grades with respect to end-use, adhesive bond requirements, panel constmetion and workmanship, scarf and finger-jointed panels, dimensional tolerances, moisture content, and packaging and loading... 

Hagemaier, D. J., End Product Nondestructive Evaluation of Adhesive Bonded Metal Joints, Adhesives and Sealants, vol. 3, Engineered Materials Handbook, ASM International, Materials Park, OH, 1990. 

Although preliminary studies suggest that face-laminations can be obtained using adhesives made from condensed tannins that pass the standards of the American Institute of Timber Construction (< ), less is known about how to formulate adhesives using these materials for end-jointing of wood. This study, funded by the USDA Small Business Innovation Research Program, was undertaken to develop adhesive formulations containing 50% of sulfite extracts obtained from the bark of southern pine trees and demonstrate their use in... 

Selection of the End-Joint Profile. Because the purpose of this work was to determine whether a portion of the phenol-resorcinol-formaldehyde adhesive used in structural end-joints could be replaced by tannin extracts from southern pine bark, it was necessary to use a structural end-joint profile design. The profile chosen was the design used by many U.S. plants for the manufacture of structural end-joints. A reproduction in natural size with a drawing showing the exact dimensions is shown in Figure 1. 

In adhesives formulated in the F- and M-Series (Table I), approximately 5 to 10 minutes at ambient temperature was required to reach an end-joint tensile strength of 500 psi, a value deemed adequate to permit gentle handling of the end-jointed members. Between 15 and 20 minutes at ambient temperature was required to reach a tensile strength of 1,500 psi (11). 

Table II. Gluebond Quality of Lodgepole Pine End-joint and Douglas-fir Parallel Laminates Obtained with the F-Series Adhesive Formulations...

Although not normally measured and not a requirement of an industry standard, the high wood failure values of the end-joints obtained with these adhesives are further evidence of water-resistant bonds. It was difficult to discern differ-... 

Peel stresses exist at the ends of adhesively bonded lap joints, especially in single-lap joints. To reduce these undesirable stresses the use of mechanical fasteners near the joint ends is sometimes recommended. As high peel stresses occur only in the immediate vicinity of the joint ends, the fasteners have to be located very close to the joint ends and cannot provide a fail-safe load path in the case of debonding. Therefore, the use of mechanical fasteners to reduce peel stresses is not recommended here. Instead the bonded joint should be correctly designed to reduce the peel stresses to an acceptable level. 

Figure U.l Ultrasonic inspection techniques, (a) Contact pulse echo with a search unit combining a transmitter and receivers, (b) Contact through transmission. Transmitting search unit on top and receiving search unit on the bottom, (c) Immersion pulse echo with search unit (transmitter and receiver) and part inspected under water, (d) Immersion through transmission with both search units (transmitter and receiver) and part under water, (e) Immersion reflector plate. Same as (c) but each unit requires a reflector plate below the part being inspected. (Ref Hagemaier, D.J., End Product Nondestructive Evaluation of Adhesive Bonded Metal Joints , Adhesives and Sealants, vol. 3, Engineered Materials Handbook, ASM International, Materials Park, OH, 1990)...

Composition. An adhesive is composed of basic raw materials, which are called binders [1] and which determine its adhesiveness (adhesion) and its internal strength (cohesion), and of frequently necessary auxiharies, which establish particular end-use and processing characteristics. The adhesiveness of an adhesive, its internal strength after setting, and its processing characteristics are the fundamental properties that determine its suitability for use in forming adhesive joints. Adhesive joints are the joints formed between substrates and adherents using adhesives. 

Structural Adhesives for Fingeijointing Lumber. A recent standard detailing the testing of finger joints when used as end joints in structural glued, laminated timbers (see also D-2559 in wood adhesive specifications). 

O Figure 22.6a shows the geometry for the tensile test. In the tensile test, two rigid cylinders are bonded end to end with adhesives, and the joint is tested by applying tensile forces on both cylinders and measuring the resulting stress-strain curves. Though the test method looks quite simple, special care has to be paid for the data analysis. In practice, the stress distribution at the adhesive-substrate interface is not uniform (see Fig. 22.6b), but depends on the elasticity (modulus and Poisson s ratio) of the cylinder and the adhesive, and also on the aspect ratio (thickness/diameter) of the adhesive (Adams et al. 1978 Anderson et al. 1977). Due to this reason, the tensile test has to be performed under (at least) controlled thickness conditions. 

These samples demonstrated exceptional durability regardless of surface preparation, due to the moisture resistant chemical and physical interlocking of the paint/adhesive interface. In addition, the zinc particles within the paint are encapsulated by the organic resin. Since few, if any, metal oxide sites are available for hydrolysis by moisture at the interface, more durable joints are the end result. 

This certificate relates to Climatube extruded foam PE pipe insulation. It is used in the thermal insulation of water supply pipes and heating pipework. The insulation is semisplit for ease of fitting, and polychloroprene adhesive and climatape adhesive tape are supplied for sealing cut ends and joints. Thermal conductivity data are tabulated. EUROPEAN COMMUNITY UK WESTERN EUROPE... 

Heis et al.19) joined superimposed skin incisions by means of the Estman-910 adhesive in experiments on rats. Having cut out a strip of glued skin of a certain size, one of its ends was immobilized, while a containement was suspended from the other end. The containement was gradually filled with water which enabled to determine the breaking load and compare it with the load that destroyed sutured skin. It is impossible, however, to estimate the strength of glueing in this case though the authors came to the conclusion that an adhesion joint was not inferior to a sutured one. 

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