Vpliv vrste lepila na sorpcijske lastnosti iverne plošče : diplomsko delo - visokošolski strokovni študij

Bozovičar, Jure (author), Medved, Sergej (mentor), Gorišek, Željko (reviewer)

Iverna plošča je zaradi svoje narave higroskopičnega materiala dimenzijsko nestabilna, kadar jo izpostavimo višji ali nižji relativni zračni vlažnosti in/ali vodi. Najpomembnejša posledica, ki jo povzroča povišanje relativne vlažnosti plošč je sprememba debeline, ki povzroča nabrekanje in krčenje lignoceluloznih iveri in sproščanje notranjih napetosti dodanih v procesu stiskanja ivernih plošč. Spremembo debeline smo merili gravimetrično in s pomočjo vertikalne porazdelitve prostorninskih mas. Primerjali smo rezultate sorpcijskih sprememb vzorcev izdelanih z urea in fenol-formaldehidnimi smolami. Klimatizirane vzorce smo izpostavili enemu ciklu vlaženja pri 85 5 % in sušenja pri 35 5 % relativni zračni vlažnosti s konstantno temperaturo 20 °C. Cikel vlaženja je trajal 648 ur, cikel sušenja pa 240 ur. Pri primerjavi rezultatov UF in FF vzorcev smo ugotovili, da je na koncu uravnovešanja v vlažni klimi relativna sprememba vlažnosti in debeline FF vzorcev znašala 18,15 % in 11,32 %; pri UF vzorcih pa 15,50 % in 4,98 %. Sprememba vlažnosti in debeline je v zunanjem sloju (ZS) pri FF vzorcih znašala 8,48 % in 6,60 % ter 17,78 % in 6,43 % pri UF vzorcih. Sprememba vlažnosti in debeline je v srednjem sloju (SS) pri FF vzorcih znašala 28,92 % in 10,44 % ter 28,92 % in 10,44 % pri UF vzorcih. Ireverzibilna sprememba debeline je na koncu enega cikla nihajoče klime pri FF vzorcih znašala 0,73 mm in 0,3 mm pri UF vzorcih. Izmerjena prostorninska masa absolutno suhih FF vzorcev je znašala 0,707 g/cm3, za ZS 0,842 g/cm3 in 0,621 g/cm3 za SS. Pri UF vzorcih je znašala izmerjena prostorninska masa 0,664 g/cm3, za ZS 0,821 g/cm3 in SS 0,577 g/cm3.

• Language: Slovenian
• Keywords: iverna plošča, lastnosti, sorpcija, vlažnost, debelina, ireverzibilna sprememba debeline, urea, fenol
• Work type: Undergraduate thesis
• Typology: 2.11 - Undergraduate Thesis
• Organization: BF - Biotechnical Faculty
• Place of publishing: Ljubljana
• Publisher: [J. Bozovičar]
• Year: 2010
• Number of pages: IX, 44 f.
• PID: 20.500.12556/RUL-487
• UDC: 630*862.2:630*824.85
• COBISS.SI-ID: 1792905
• Publication date in RUL: 11.07.2014

Secondary language

• Language: English
• Title: Impact of adhesive type on the sorption properties of particleboard : graduation thesis - higher professional studies

Abstract

Because of the nature of hygroscopical material particleboards are dimensionally unstable when exposed to relative humidity or water. The most significant effect, caused by increasing moisture content of the boards, is the change in its thickness. The change of the thickness induces swelling of lignin-cellulose particles and releases imparted compressive stress in the process of pressing. The change of the thickness was measured gravimetrically, and with help of vertical distribution of density. Urea-formaldehyde (UF) and phenol-formaldehyde (PF) particleboard samples were studied and compared. Samples were exposed to 1 cycle of moisturising at 85 5 % and drying at 35 5 % of relative humidity with constant temperature at 20 °C. The cycle of moisturising took 648 and drying 240 hours. It was found that relative swelling of FF samples added up to 11.32 % and 4.98 % for UF samples. It was also found that relative moisture change of FF samples was 18.15 % and 15.50 % for UF samples. Moisture change of outer layer of FF samples was 8.48 % and 17.78% for UF samples. Its relative thickness swelling of FF samples was 6.60 % and 6.43 % for UF samples. Moisture change of inner layer of FF samples was 28.92 % and 28.92 % for UF samples. Its relative thickness swelling of FF samples was 10.44 % and 10.44 % for UF samples. At the end of oscillating humidity the springback of FF samples was 0.73 mm and 0.3 mm for UF samples. Measured absolute dry density of FF samples was 0.707 g/cm3, for outer layer 0.842 g/cm3 and 0.621 g/cm3 for inner layer. The measurements of UF samples were 0.664 g/cm3, for outer layer 0.281 g/cm3 and 0.577 g/cm3 for inner layer.

• Keywords: particleboard, sorption properties, thickness swelling, springback, urea, phenol