bioresources. com
PEER-REVIEWED ARTICLE
The plasma was applied to 100 g of wheat straw for 4 min, and during the treatment, the Alther 2590 digital thermometer (Ahlborn Mess- und Regelungstechnik GmbH, Holzkirchen, Germany) recorded the maximum temperature inside the particle blend. The degree of plasma surface activation of particles was evaluated with the use of Arcotest (Arcotest GmbH, Moensheim, Germany) test inks designed to measure surface tension. The ink value was identified 2 s after it was applied to the surface, and then an image was recorded using the DTX 90 digital microscope (Levenhuk, Tampa, USA). Testing was conducted until the ink started to coalesce into drops. When it coalesced, a lower-value ink was used, and the boundary between the two inks was sought out. $GKHVLYHPL[WXUHDSSOLFDWLRQ After activation of the surface, the particles were resinated with a preformed urea- formaldehyde (UF), hardener (ratio solids hardener / dry adhesive was 10%), and paraffin emulsion mixture (ratio solids hydr. agent / dry particles was 1%). The solid content was 50%. A resin dosage of 10% solids on wood dry mass was applied in a planetary mixer M 301 (Bonnet, Mitry-Mory, France). The mixture was subsequently placed in a drying chamber EHR-K 15/40/20 II (Helios Ventilatoren GmbH, Villingen-Schwenningen, Germany), where it was dried at 30 °C to a moisture content of 8%. The ISI10 scale (Sartorius AG, Göttingne, Germany) was used to continuously monitor water loss, and the final moisture was determined on a moisture tester Ultra X 3011 instrument (A&P instruments, Detmold, Germany). 9LD gradual pouring, the prepared mixture (175 g) was manually layered into a mold with internal dimensions of 128 mm × 355 mm. The layer was spread evenly along the horizontal guiding lines on the inside of the mold. 3UHSUHVVLQJDQGKRWSUHVVLQJ The mold was then closed and a cold pre-press was performed on the HLP350 hydraulic press (Höfer Presstechnik GmbH, Taiskirchen, Austria). The pressing conditions were set manually by means of the controller to an initial pressure of 4 bars for 1 min. The pre-pressed board was then removed from the mold and continued to be pressed by two heated plates set to 165 °C. The pressing plates were always separated on both sides using waxed paper to avoid adhesion of the boards to the press plate. The pressing was performed according to the pre-set program on the resulting board thickness of 6 mm. The press cycle is shown in Table 2. The total number of six boards for each variant was manufactured. The boards were then allowed to cool down and, further on, they were conditioned at 20 °C and a relative humidity (RH) of 65% for 14 days. Table 2. Pressing Cycle Phase No. Thickness at the End (mm) Moving Time (s) Remaining Time (s)
1 2 3 4 5 6 7 8
40
0.1
0 0 6 5 0 0 0
9
4 4 5 3 3
5.9
6
6.3
6
50
6.5 500
25 0.1
5068
Hýsek et al . (2018). “Cold plasma & straw board,” B io R esources 13(3), 5065-5079.
Made with FlippingBook Ebook Creator