Adhesives for Wood and Lignocellulosic Materials. R. N. Kumar. Читать онлайн. Newlib. NEWLIB.NET

Автор: R. N. Kumar
Издательство: John Wiley & Sons Limited
Серия:
Жанр произведения: Техническая литература
Год издания: 0
isbn: 9781119605669
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5–5 Biphenyl 10–11 5 4–0–5 Diaryl ether 4 7 β-1 1,2-Diaryl propane 7 7 β-β Linked through side chains 2 3

      a Approximate values based on data of Adler [26] obtained for MWL from spruce (Picea abies) and birch (Betula verrucosa).

      b For corresponding structures.

      c Values have been reported [25].

      d Of these structures, about 40% are of guaiacyl type and 60% are of syringyl type.

      Penetration of adhesive into the porous network of wood cells is believed to have a strong influence on bond strength [28–30].

      1.5.1 Penetration

       1.5.1.1 Penetration in Different Size Scales

      Laborie proposed a categorization of adhesive penetration in wood in terms of different size scales of adhesive penetration [32]. Accordingly, in the following classification, four scales of penetration are envisioned:

      1 Macroscopic penetration (millimeters)

      2 Microscopic penetration (microns to tens of microns)

      3 Nanoscale penetration (nanometers to tens of nanometers)

      4 Angstrom scale penetration (up to tens of angstroms)

Component μm nm
Adhesive force 0.0002–0.0003 0.2–0.3
Cell wall pore diameter 0.0017–0.002 1.7–2.0
PF resin molecular length 0.0015–0.005 1.5–5.0
Diameter of particles that can pass through a pit 0.2 200
Tracheid lumen diameter 4–25
Glue line thickness 50–250

      In order to understand the adhesion phenomenon operating at different size scales in wood, the values of size scales shown in Table 1.2 should be viewed in conjunction with the length scale (as shown in Table 1.3) [37] over which different wood–adhesive interactions take place.


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Category of adhesion mechanism Type of interaction Length scale
Mechanical Interlocking or entanglement 0.01–1000 μm
Diffusion Interlocking or entanglement 10 nm-2 nm
Electrostatic Charge 0.1–1.0 μm
Covalent bonding Charge 0.1–0.2 nm
Acid-base interaction Charge