Thickness Swelling Test

After the boards were removed from the hot press they were conditioned at room temperature for several days before testing. Three 2 x 10-inch strips were cut from each board for determining breaking load. A 0.24-inch-per-minute loading rate and a 9-inch span were used. Thickness of each strip was measured at the point where the load was to be applied, and after the strip had been "broken each half was cut into two 2 x 2-inch samples. These samples were used to obtain data necessary for determination of oven-dry density, water absorption and thickness swelling, internal bond, and a 2-hour boiling-in-water thickness swelling test. 

Hygroscopic thickness swelling Water absorption JIS A 5908 Particleboards 5.8 Hygroscopic thickness swelling test... 

Table 16.3 Evaluation of water absorption and thickness swelling test of various formulated hybrid composites.

U50 000 psi IB, minimum = 60 psi and linear expansion, maximum = 0.25. Properties of all examples given in Table II substantially surpass the comercial standard and also surpass the properties of the PF control boards with respect to linear expansion, thickness swelling, and absorption in the one-hour boil test. Internal bonds, both initial and after the one-hour boil test, and water immersion results of the HDA experimental boards were slightly inferior to results of these tests for the PF control boards. Properties of urea-formaldehyde control boards were similar to the PF control boards excepting in the one-hour boil test where complete failure of all bonding took place in about 15 minutes. 

Bark Extracts Density O.D. (gm/cc) Modulus of Rupture (psi) Internal Bond (psi) 24-hr Water Absorption (%) Immersion Thickness Swelling (%> 2-hr Boil Test Thickness Swelling (%> Linear Expansion (%)... 

Dost in 1971 reported on a study where redwood bark fiber was used in three-layer particleboard (44). Amount of bark in the furnish, by weight, was 0, 10, 20, and 30% hammemilled disk flakes or Pallmann flakes of redwood wood made up the remainder of the furnish. Urea formaldehyde resin was applied at three percentages. Test results showed surface smoothness and strength properties (MOR, MOE, and IB) decreased with increasing bark content in the boards. Water absorption decreased, but thickness swelling and linear expansion increased as the amount of bark increased. 

So far this year, two reports have been published on the effect of bark in medium-density fiberboard. The first by Woodson (61) covered the bark of three southern hardwoods, sweetgum, southern red oak, and mockernut hickory percentage of bark in the whole-tree furnish was 13.4, 20.0, and 18.6%, respectively. Urea-melamine formaldehyde binder was added at 8-10%, and wax at 1%. Test results showed inclusion of bark decreased tensile and bending strengths by 16-18%, MOE by 10-14%, and IB by 8%. Linear expan sion was not affected significantly by bark. Thickness swelling was improved in two of the three species. Woodson concluded good quality, medium-density fiberboard could be made from barky chips. 

In Table V, the mechanical properties of particleboard bonded with nonemulsifiable diisocyanate modified with maize starch are given. The extender content for the diisocyanate was up to 20%. However, with increasing extender content, the internal bond of the boards decreased, and the thickness swelling increased the boards had V100 quality. First tests with adhesives of diisocyanates and starch were encouraging, and more attempts in developing new glue formulations... 

Note Data for HMDA with nonpreoxidized wood are from Ref. 82 all other data are from Refs. 83 and 84. Thickness swelling refers to 1-h boil test, except for the last two numbers which refer to 2-h immersion (temperature not given). 

Fig. 9 Effect of undefibrized paper particles on thickness swelling in 24 hr water soak test...

The effects of a test substance on the cornea are measured quantitatively as an increase in thickness (swelling), subjectively as scores for corneal opacity, the area of corneal involvement, fluorescein penetration, and morphological changes to the corneal epithelium. Two additional endpoints may be incorporated into the protocol or used ad hoc to supplement existing data. This includes the use of histopathology to confirm or identify the extent of irritancy at the histology level (especially if the irritancy fells between moderate and severe) and the use of confocal microscopy to determine the extent and depth of ocular injury [69, 70], see also Section 4.2.3. 

The pattern used for cutting test specimens is shown in Figure 3. The property values given in this report are mean values of the number of specimens indicated times two since each board was duplicated. Densities were measured on all thickness swell, internal bond (IB) and bending modulus specimens before those respective tests were run. 

The ASTM procedure covers an extended set of tests of wood-based materials, among them (Sections 100-111) tests for water absorption and thickness swelling, and for moisture content. The procedure describes two water absorption methods Method A, for 2 plus 22 h submersion period, and Method B, for single continuous... 

Test results showed inclusion of bark decreased tensile and bending strengths by 16-18%, MOE by 10-14%, snd IB by 8%. Linear expansion was not affected significantly by bark. Thickness swelling was Improved in two of the three species. Woodson concluded good quality, medium-density fiberboard could be made from barky chips. 

Figure 11 Typical trends of irreversible thickness swelling characteristics of wood particleboard bonded with MF and PF adhesives during a wet-dry cycle test.

Fig. 42 Swelling test results (a) weight increments (b) length increments on plane (c) thickness increments...

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