Review of forests, wood products and wood biotechnology ... - GWDG

The water affinity of the produced boards is tested with the thickness swelling test
after 24 hours of water storage. The results are shown in figure 5.
swelling 24h [%]
50
45
40
35
30
25
20
15
10
5
0
0% 1% 2% 3% silane
14,3
15,4
8,8
11,5
Thickness Swelling
25,7
19,5
16,3
Figure 5: Mechanical technological properties of particle boards produced with
modified binding agents – 20 mm particle boards; 200 °C; 3 min; 700 kg/m³; glue
ratio: 11 % / 8.5 % - Thickness Swelling after 24h of water storage
The results for the thickness swelling test show the high stake of the rate of urea
formaldehyde substitution with protein on the observed thickness swelling. The
higher the amount of wheat protein the higher is the water affinity of the boards.
The unsubstituted urea formaldehyde binder shows a thickness swelling of 14.3 %
whereas the boards produced with the 25 % protein substituted binder systems
posses a thickness swelling of 25.7 %. With the 50 % protein substituted binder
produced boards where totally destroyed during the water storage test.
By adding silane in low amounts it is possible to reduce the water affinity of
the particle boards. For the unsubstituted urea formaldehyde boards it was
possible to reduce the swelling to 8.8 % by adding 2 % of silane. For samples
produced with the 25 % protein substituted urea formaldehyde binder the swelling
was reduced from 25.7 % to a level of 16.3 % witch is close to the EN 312
restriction. But it was successful to increase the amount of silane to a level higher
than 2 %
The 50 % protein substituted samples where totally destroyed during the
water swelling test, witch can be explained with the very low mechanical
properties of the variant.
30,3
Ref UF 25P UF50P
19
13