Uporaba infrardeče spektroskopije za spremljanje utrjenosti premazov za les : diplomsko delo (univerzitetni študij)

Voljč, Peter (author), Petrič, Marko (mentor), Tišler, Vesna (reviewer)

Prikazali smo uporabnost infrardeče spektroskopije (FT-IR) za spremljanje utrjenosti premazov za les. Uporabljali smo nitrocelulozni (NC) premaz, ki utrjuje fizikalno in kemijsko utrjujoč poliuretanski (PU) premaz. Sprva smo utrjenost premazov, nanesenih na steklene plošče, spremljali s standardnimi metodami (spremljanje izgube mase med utrjevanjem, stopnja utrjenosti po DIN 53150 in ocenjevanje trdote po DIN 53157), nato pa smo pričeli s snemanjem vzorcev premazov z infrardečim spektrometrom. Vse meritve so od nanosa premazov trajale 28 dni. Uspelo nam je posneti FT-IR (nihajne) spektre premazov med utrjevanjem. Z metodo spremljanja izgube mase med utrjevanjem smo opazovali intenzivno zmanjševanje mase NC premaza prvih 20 min po nanosu, pri PU premazu pa nekoliko dlje (25 min). Masa se je pri PU premazu ustalila že po 60 min, pri NC premazu pa po 180 min utrjevanja. Z metodo po DIN 53150 smo ugotovili, da sta oba premaza dosegla 1. stopnjo utrjenosti po 20 min; 7. stopnjo utrjenosti je PU premaz dosegel že po 130 min, NC premaz pa po 330 min. PU premaz je torej utrjeval hitreje od NC premaza. Pri metodi po DIN 53157 smo največje spreminjanje trdote opazili v 24 urah po nanosu, naraščanje trdote pa smo, pri obeh premazih, zaznavali še do 2 tednov. Trdota je hitreje naraščala pri PU premazu, kar je posledica procesa kemijskega utrjevanja. Z metodo FT-IR smo pri obeh premazih opazili odparevanje topil, po 24 urah pa tega nismo več mogli potrditi. Proces kemijskega utrjevanja smo pri PU premazu zaznali še po 28 dneh, to je po daljšem času, kot ga za utrjevanje vseh premazov navaja standard. Ugotovili smo torej, da je infrardeča spektroskopija ustrezna metoda za spremljanje utrjevanja premazov za les, predvsem kemijsko utrjujočih.

• Language: Slovenian
• Keywords: les, površinska obdelava, premazi, PU, NC, utrjevanje, FT-IR
• Work type: Undergraduate thesis
• Typology: 2.11 - Undergraduate Thesis
• Organization: BF - Biotechnical Faculty
• Place of publishing: Ljubljana
• Publisher: [P. Voljč]
• Year: 2006
• Number of pages: XII, 67 f.
• PID: 20.500.12556/RUL-142
• UDC: 674.07
• COBISS.SI-ID: 1442953
• Publication date in RUL: 11.07.2014

Secondary language

• Language: English
• Title: Application of infrared spectroscopy for observation of hardening of wood coatings : graduation thesis (university studies)

Abstract

The applicability of infrared spectroscopy (FT-IR) for observation of hardening (drying or curing) of wood coatings is presented. The nitrocellulose (NC) coating, which dries physically, and the polyurethane (PU) coating, which cures chemically, were observed. At first, hardening processes of coatings spread onto glass plates were surveyed by some standard methods (determination of mass loss during drying or curing, degree of hardness according to DIN 53150, and estimation of hardness according to DIN 53157). Subsequently, infrared spectra of the coatings were recorded. The FT-IR measurements were performed within 28 days after application of the coatings. Recordings of FT-IR (vibrational) spectra of the coatings during the drying/curing processes were successfully done. Observation of mass losses during drying/curing exhibited a remarkable decrease of the NC coating mass in the first 20 minutes after application. The process for the PU coating hardening lasted a bit longer (25 minutes). The mass of the PU or NC coating stabilized already after 60 or 180 minutes, respectively. According to the DIN 53150 it was established that both coatings reached the first degree of hardness after 20 minutes of the hardening process. The PU coating reached the 7th degree of hardness already after 130 minutes, and the NC coating after 330 minutes. Therefore, the PU coating hardened faster than the NC coating. Using the DIN 53157 method, the most prominent changes of hardness were observed in the first 24 hours after the coating application. However, the increase of hardness of both coatings was noticed still after 2 weeks. The hardness of the PU coating increased faster, which was the consequence of a chemical curing process. FT-IR method exhibited evaporation of solvents from both coatings, but after 24 hours this could no longer be confirmed. The chemical curing process in the PU coating could still be noticed after 28 days after application, longer than demanded for hardening to be finished according to the standard. It can be resumed, that infrared spectroscopy is a suitable method for observation of the hardening (drying or curing) processes in wood coatings, above all for those curing chemically.

• Keywords: wood, surface finishing, coating, PU, NC, hardening, FT-IR