Internal bond strength

For the resultant 8 x 8 x j -in. board board density = 40.67 Ib/ft3 internal bond strength (ASTM D1037) = 133 psi thickness swell (ASTM D1037) = 18.8%. 

The production of moisture resistant particleboard by treatment with a maleic anhydride -glycerol mixture and using phenol formaldehyde as the matrix material has been investigated (Fujimoto etal., 1987). Boards prepared from modified wood showed considerable improvements in modulus of elasticity and internal bond strength when compared to control boards. Composites made from aspen fibres modified with SA, MA or acetic anhydride using phenol-formaldehyde (PF) or polypropylene as binder have also been studied (Clemons etal., 1992 Rowell etal., 1993b). The reaction of wood with MA was found to proceed at a slower rate than with SA. The volume increase due to modification... 

Imamura, Y., Nishimoto, K. and Rowell, R.M. (1987). Internal bond strength of acetylated flake-board exposed to decay hazards. Mokuzai Gakkaishi, 33(12), 986-991. 

After a l6-week exposure to T. palustris, the internal bond strength of control aspen flakeboards made with phenol-formaldehyde... 

Estimating the Adhesive Quality of Lignins for Internal Bond Strength... 

IB = internal bond strength F = suffix used to indicate methylolated sample WtpF = weight of PF resin in a lOOg board WtML = weight of methylolated lignin in a lOOg board Rf = total aliphatic OH index Ra = total alcohol index... 

Figure 12.—Internal bond strength of boards described in Figure 11...

Results of the later studies showed bark-paraformaldehyde furnish as core of three-layer particleboard resulted in white fir boards meeting medium-density particleboard specifications for bending and internal bond strengths, as well as linear expansion (51). 

Table IV. Internal Bond Strength of Particleboard, 12-mm-Thick, Prepared from Soda Bagasse Lignin Adhesives (10% on Dry Chips) After Pressing at 170 °C for 15 Minutes...

Publication Date December 31, 1989 doi 10.1021/bk-1989-0385.ch007 Internal Bond Strength (MPa)... 

The internal bond strength recovery was determined after the specimens (24 hr water immersed) were dried in an oven at 103 2 °C until approximately constant weight was obtained. 

More recently, fiberboards have been made from acetylated bagasse fiber [58] and acetylated aspen fiber [59,60]. The fiberboards swelled at a much slower rate and to a lesser extent than control fiberboards [58], and their internal bond strength [58] and biological resistance [59] were greater. 

Kiguchi and Yamamoto [11] prepared hot-melt, self-bonded particleboards from benzylated wood particles. Their internal bonding strengths were about twice those of conventional particleboards. The interparticle bondings of the benzylated particleboards were plane adhesion. 

On the other hand, the internal bond strength of benzylated boards manufactured using particles with 51 WPG was about two times higher than that of a conventional board (Fig. 22). The bonding between particles in conventional particleboard is via point adhesion, whereas in hot-melt and self-bonded boards it occurs by plain adhesion. Accordingly, the internal bond strength... 

Figure 22 Internal bond strength of surface-benzylated and self-bonded boards. Abbreviations are the same as in Fig. 21. (From Ref. 32.)...

Using an isocyanate resin, at 3% solids content, on the same aspen flakes as described above, dry internal bond strength decreased by only 2%, MOR decreased by 23%, and MOE decreased by 15% on boards made from acetylated flakes as compared to boards made from nonacetylated flakes [37]. This is just one more example of how the type and level of the resin used influenced composite board mechanical properties. 

Solvent effects are less dominant in the isomerization of the phosphole complexes than in the isomerizations of the phosphine complexes. Likewise changes in internal bond strengths are more important for the phosphole complexes than for the phosphine complexes. This is because both the Pd-P and Pd-X bonds are stronger and shorter in the phosphole than in the phosphine complexes suggesting that DMPP is both a better a-donor and r-acceptor toward Pd(II) than is Me2PPh. 

Figure 3. Relationship between board density and internal bond strength in particle board made by direct oxidative wood-to-wood bonding. Key , 0.2% FeSO.-4.0% HJD.-0.5% H.PO.-0.5% HCl and O, 0.2% FeSO -4.0% H202-1.0% H PO (77).

The curing conditions are equally important for reducing formaldehyde emission. The curing process is not yet fully understood. In fact, there is even still some question about the nature of the reactive resin. The latter subject is described in a later chapter by Johns. Appropriate resin cure conditions must take into account the wood moisture content and wood acidity, as well as resin concentration, temperature gradients, and press duration. In excessively cured UF bonded wood products, and in products that are stacked while still hot from the press, UFR can hydrolyse so strongly that particleboard loses internal bond strength. 

Press Time. Properties of the Mondur MR-bound boards pressed only 3 minutes vs. those of the control boards are given in Table XI. The internal bond strength of the Mondur MR boards did drop, as expected, although even at 3 minutes press time at 325 F (l63°C), it is higher than that of the phenolic-bound board cured 7 minutes at 375 F (191 C). The surprise comes in the bending strength and durability properties where the performance actually appears better at the shorter press time. 

Swelling after 2 h boil Internal bond strength ... 

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