Razvoj trdnosti spoja pri lepljenju lesa z biolepili na osnovi tanina in lignina

Saražin, Jaša (avtor), Šernek, Milan (mentor)

Svetovna poraba lepil za les se vsako leto veča. Ker so najpogosteje uporabljana sintetična lepila, ki obremenjujejo okolje in so lahko zdravju škodljiva, je iskanje okoljsko primernejših alternativ predmet raziskav že nekaj desetletij. Tanini in lignini, kot najizdatnejši obnovljivi viri polifenolnih spojin, se nakazujejo kot najprimernejša alternativna surovina, saj bi z njimi količinsko lahko v celoti nadomestili zdaj uporabljana sintetična lepila. V tej raziskavi sta bili proučevani dve biolepili – tanin-heksaminsko (TH) in organosolv lignin brez-izocianatno poliuretansko (NIPU) in primerjani med seboj ter s komercialnim urea-formaldehidnim lepilom (UF). Za lepila je bila izvedena osnovna karakterizacija v tekočem stanju ter končna karakterizacija po utrjevanju, na podlagi katere so bila vsa tri preizkušena lepila razvrščena v trajnostni razred C1, kar pomeni da so ustrezna za nekonstrukcijsko notranjo rabo. Proces utrjevanja je bil proučevan z metodami ABES, DSC, DMA in DEA za spremljanje razvoja trdnosti lepilnega spoja. Na podlagi rezultatov več metod je bilo ugotovljeno, da lepilo UF utrjuje najhitreje, sledi mu lepilo TH, najpočasneje pa utrjuje lepilo NIPU. Optimalni časi in temperature stiskanja so bili določeni upoštevajoč rezultate referenčne metode ABES. Ti so za TH lepilo bili 4 min pri 175 °C, za lepilo NIPU 7 min pri 200 °C ter za UF lepilo 1,5 min pri 100 °C. Obstoj splošnih zakonitosti, ki bi na podlagi rezultatov posrednih metod napovedale razvoj trdnosti lepilnega spoja, določenega z referenčno metodo ABES, ni bil dokazan. V splošnem pa je bilo ugotovljeno, da metoda DEA nekoliko preceni proces utrjevanja, določen z metodo ABES, metoda DSC ga v prvem delu podceni, vendar dobro določi njegovo končno utrjenost, medtem ko ga metoda DMA podceni.

• Jezik: Slovenski jezik
• Ključne besede: biolepila, tanin, lignin, dinamika graditve trdnosti, ABES, DSC, DMA, DEA
• Vrsta gradiva: Doktorsko delo/naloga
• Tipologija: 2.08 - Doktorska disertacija
• Organizacija: BF - Biotehniška fakulteta
• Kraj izida: Ljubljana
• Založnik: [J. Saražin]
• Leto izida: 2022
• PID: 20.500.12556/RUL-135690
• UDK: 630*824.82:674.028(043.3)
• COBISS.SI-ID: 102765571
• Datum objave v RUL: 26.03.2022

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Bond strength development at bonding of wood with bioadhesives based on tannin and lignin

Izvleček

Global consumption of wood adhesives is increasing every year. Due to the environmental and health concerns related to the most commonly used synthetic adhesives, biobased adhesives are gaining substantial interest. Tannins and lignins, as the most abundant renewable sources of polyphenolic compounds, are considered the most suitable alternative raw material that could completely replace the currently used synthetic adhesives. In this study, two biobased adhesives, tannin-hexamine (TH) and organosolv lignin non-isocyanate polyurethane (NIPU), were studied and compared with each other and with commercial urea-formaldehyde (UF) adhesive. The basic characterization in the liquid state and the final characterization of the studied adhesives were performed. All three adhesives tested were classified as C1 durability class, which means that they are suitable for non-structural interior applications. The curing process was studied using ABES, DSC, DMA, and DEA methods to monitor the curing process of the adhesive bond. Based on the results of different methods, it was found that the curing process of UF adhesive is the fastest, followed by TH adhesive and the NIPU adhesive curing process as the slowest. The optimum pressing times and temperatures were determined by considering the results of the ABES reference method. These were 4 min at 175 °C for the TH adhesive, 7 min at 200 °C for the NIPU adhesive, and 1.5 min at 100 °C for the UF adhesive. The existence of general models for predicting the adhesive bond strength development determined by the ABES reference method based on the results of indirect methods has not been proven. In general, it was found that the DEA method slightly overestimates the curing process determined by the ABES method; the DSC method underestimates it in the first part but determines its final cure adequately, while the DMA method underestimates it.

• Ključne besede: bioadhesives, tannin, lignin, bond strength development, ABES, DSC, DMA, DEA