The research dealt with the possibility of using hay for the production of large-area material. Boards with a density of 630 ± 30 kg/m3 and thickness of 12 mm were pressed from the hay. The boards were made of hay fractions and whole hay straws. Due to the presence of a water repellent waxy coating of the surface layers of the hay straws, the hay was soaked in NaOH solution to disrupt the coating and increase the surface wettability for the water-based adhesives. The soaking was carried out with different temperatures, time, and concentrations. Depending on the measurements of the contact angle of the water drop on the hay surface, a 5% NaOH solution was selected. The FR 15 and FR 60 boards were made from a hay fraction soaked at the temperature 20 ° C for 15 minutes and 60 minutes. A reference board FR REF was produced in the same way without chemical treatment. For comparing the boards' properties, several boards were produced: a DTD ST board was made of wood chips used for the central layers of boards made by the Kronospan company; a board NE REF, produced from the whole hay straws without any chemical treatment; a board NE 15, which was made out of hay undergone 15 minutes long treatment at 20 °C. UF resin (Kronores CB 1637), which is used for bonding of the core layers of particle boards, was used as the adhesive. The results have shown that the wettability of the straw surface can be improved by the chemical treatment by almost 50% compared to the hay without treatment. The contact angle values of the hay without the chemical treatment were 92,2 °. In hay soaked in NaOH solution, the contact angle decrease to 45 °. However, the hay treated this way wasn't suitable for board production due to its significant degradation. The hay used for boards FR 15 and FR 60 had values of 63 and 62, 9 ° accordingly, which were similar to those measured on the wood surface (64 °). Properties of the produced samples were tested according to ČSN EN standards. In bending tests, boards made from hay fractions with chemical treatment reached better results at MOR compared to the reference boards (the board FR 15 - 4,5 MPa, the board FR 60 - 5 MPa, and the board FR REF - 1,3 MPa). As for the modulus of elasticity MOE, the board FR 15 reached 1710 MPa, the board FR 60 - 1703 MPa, and the board FR REF - 651 MPa. After 24 hours, the following swelling values were indicated: FR REF - 23,2 %, FR 15 - 26,6 % a FR 60 - 17,1 %. After soaking in water for 48 hours, the FR REF fraction board had shown a swelling value of 60,5 %. The boards FR 15 and FR 60 from chemically modified hay have achieved better results of 42 and 47,2 % accordingly.
| Identifer | oai:union.ndltd.org:nusl.cz/oai:invenio.nusl.cz:428359 |
| Date | January 2019 |
| Creators | Červenka, Jan |
| Source Sets | Czech ETDs |
| Language | Czech |
| Detected Language | English |
| Type | info:eu-repo/semantics/masterThesis |
| Rights | info:eu-repo/semantics/restrictedAccess |
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