1. Exploratory study on the bending performance of thermo-hydro-mechanically densified Scots pine (Pinus sylvestris L.) at elevated temperaturesLei Han, Matthew Schwarzkopf, Jaka Gašper Pečnik, Wilson Ulises Rojas Alva, Andrea Lucherini, Andreja Kutnar, Dick Sandberg, 2024, other scientific articles Abstract: Thermo-hydro-mechanical (THM) densification is a well-known wood modification procedure for improving the mechanical properties of low-density wood species, but its performance at elevated temperatures is not well understood. The objective of this study was to determine the bending behaviour of densified Scots pine at elevated temperatures. A total of 48 specimens (200 mm (longitudinonal) × 20 mm (radial) × 20 mm (tangential)) were tested to investigate the bending performance under constant temperatures at 25, 50, 125 and 175°C, respectively. It was found that the modulus of rupture (MOR) and modulus of elasticity (MOE) of both un-densified and densified pine decreased with increasing temperature. However, the densified wood exhibited more brittle shear failure but retained higher MOR and MOE than the untreated specimens treated at the same temperature level. In general, the results demonstrate that densification can be a potentially effective method to retain the mechanical properties of wood at elevated temperatures, thereby having a potential maintain the load-bearing capacity during and after fire.
Keywords: densification, wood, fire safety
Published in DiRROS: 28.11.2024; Views: 763; Downloads: 690
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4. Densification of woodAndreja Kutnar, Milan Šernek, 2007, review article Abstract: The paper treats the processes involved in wood densification and provides a summary of the state-of-the-art, as presented in the literature, with regard to densification as achieved by compression, accompanied by some form of hydrothermal treatment. The viscoelastic nature of wood is discussed, togetherwith its thermal softening and typical stress-strain relationships. The properties of densified wood products depend, apart from processing parameters, on various anatomical features such as density, the percentage of late wood material, ray volume and the loading direction. The problems associated with wood stabilization after densification are also treated. Relevant examples of wood densification from fundamental research, and the results of applied studies significant for everyday practice, are presented. Aspecial focus is given on the process of viscoelastic thermal compression (VTC) of wood.
Keywords: wood, densification, softening, transverse compression, viscoelasticity, glass transition temperature
Published in DiRROS: 12.07.2017; Views: 5328; Downloads: 2300
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5. Proteinska lepila na osnovi soje, krvi in kazeina nekoč in danesDoroteja Vnučec, Milan Šernek, Andreja Kutnar, Andreja Goršek, 2017, original scientific article Abstract: V članku je podan pregled razvoja proteinskih lepil na osnovi soje, krvi in kazeina. Članek obravnava formulacije in tehnologije lepljenja teh proteinskih lepil iz obdobja 1930-1960 ter današnje komercialne formulacije. V tem obdobju so bile namreč poraba ter tehnološke izboljšave proteinskih lepil na vrhuncu. Pri obravnavi današnjih formulacij in tehnologij lepljenja je poudarek na sojinih lepilih, saj se le-ta uporabljajo v industriji lepljenja dekorativnih vezanih, ivernih in vlaknenih plošč ter parketa. Kazein se danes uporablja le še v lepilih za protipožarna vrata, medtem ko se živalska kri v lepilih ne uporablja več. Proteinska lepila iz obdobja 1930%1960 sicer ne ustrezajo zahtevam današnjih standardov in se zato več ne uporabljajo, so pa vse opisane tehnologije še vedno uporabne in se lahko ponovno uvedejo, če bodo svetovni viri nafte usahnili.
Keywords: proteinska lepila, les, soja, kri, kazein, formulacije, tehnologija lepljenja
Published in DiRROS: 03.07.2017; Views: 7919; Downloads: 4000
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