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Table 3. Density of Straw Board at 25 °C and 65% Relative Humidity
Modification A B
Density
Ref.
Mean (kg/m 3 ) Median (kg/m 3 )
540.0 524.9 545.7 540.5 528.8 553.4
Standard deviation (kg/m 3 ) Minimum (kg/m 3 ) Maximum (kg/m 3 )
27.9
31.5
31.0
486.2 473.8 491.8 613.2 586.4 607.1
a
b
Fig. 4. (a) Vertical density profile of straw boards at 25 °C and 65% relative humidity; (b) side view of pressed board with nominal thickness of 6 mm (TXLOLEULXPPRLVWXUHFRQWHQWDQGWKLFNQHVVVZHOOLQJ Figure 5 shows a graph of the dependency of equilibrium moisture content of the boards on relative humidity, and Fig. 6 shows a graph of the dependency of thickness swelling on relative humidity, and these average values are subsequently specified numerically in Table 4. The highest values of equilibrium moisture and thickness swelling were obtained from boards manufactured fromparticles modified by a higher degree of plasma treatment (type B), and all of the differences in the given moisture level were statistically significant (Table 5). Adversely, the lowest values of equilibrium moisture were obtained from the boards manufactured from unmodified particles. In terms of the equilibrium moisture of boards manufactured from particles treated with a lower degree of plasma treatment and untreated particles, a statistically significant difference only appeared in the first air-conditioning stage (20 °C/RH 65%, absorption cycle). Type B boards once again exhibited the highest thickness swelling. As expected, the lowest values of thickness swelling were not reached by boards from the reference particles (Fig. 6). Except for in the first air-conditioning stage (this difference was not statistically significant (Table 6)), a higher thickness swelling in the reference boards was ascertained than in the boards manufactured from modified particles with a lower degree of plasma treatment. This was explained by a variation in the average density of boards, where the average density of the reference boards was 540.0 kg/m 3 and boards with a lower degree of modification reached 524.9 kg/m 3 .
5072
Hýsek et al . (2018). “Cold plasma & straw board,” B io R esources 13(3), 5065-5079.
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