Title Postojanost poliakrilatnih nanopremaza na toplinski modificiranom drvu Title (english) Durability of polyacrylate nanocoatings on thermally modified wood Author Josip Miklečić Mentor Hrvoje Turkulin (mentor)Committee member Boris Ljuljka (predsjednik povjerenstva)Granter University of Zagreb Defense date and country 2016-10-14, Croatia Scientific / art field, BIOTECHNICAL SCIENCES Universal decimal classificationUDC ) 620 - Materials testing. Power stations. Economics of energy Abstract Toplinski modificirano drvo zaštićeno prozirnim premazima još je uvijek podloţno površinskoj razgradnji uslijed djelovanja vanjskih utjecaja. U ovom radu istraţena je mogućnost povećanja postojanosti prozirnih premaza na toplinski modificiranom drvu dodavanjem nanoĉesica TiO2 i ZnO u poliakrilatni vodeni premaz. Nemodificirani i toplinski modificirani uzorci bukovine površinski neobraĊeni i obraĊeni s devet sustava poliakrilatnih vodenih premaza izlagani su ubrzano i prirodno vanjskim okolišnim utjecajima. Provedena su mjerenja boje, sjaja, pojave pukotina, ljuštenja i plijesni, mehaniĉkih i toplinskih svojstva, transmitancije premaza i kemijskih promjena.Provedeno istraţivanje pokazalo je da toplinska modifikacija bukovine smanjuje gustoću, povećava kiselost, izrazito smanjuje polarnu komponentu slobodne površinske energije, povećava udio lignina, vodenog i otapalnog ekstrakta. Dodatak ZnO nanoĉestica imao je veći utjecaj na svojstva tekućeg poliakrilatnog vodenog premaza od TiO2 nanoĉestica. Dodatak ZnO nanoĉestica povećao je viskoznost premaza uz povećanje pH vrijednosti. TiO2 i ZnO nanoĉestice povećale su ĉvrstoću, modul elastiĉnosti i staklište, a smanjile istezanje poliakrilatnog vodenog premaza. Dodatkom TiO2 i ZnO nanoĉestica u pliakrilatni vodeni premaz smanjila se promjena boje sustava toplinski modificirano drvo premaz tijekom prirodnog i ubrzanog izlaganja, ali je i dalje bila vrlo izraţena i jasno vidljiva ljudskom oku. Bolji uĉinak stabilizacije promjene boje postignut je s TiO2 nanoĉesticama i povećanjem koncentracije nanoĉestica. Predobrada toplinski modificiranog drva otopinom HALS spojeva nije bila uĉinkovita u zaštiti od promjene boje tijekom prirodnog i ubrzanog izlaganja. Dodatak pigmenata u premaze s nanoĉesticama TiO2 i ZnO najviše je stabilizirao promjenu boje toplinski modificiranog drva tijekom ubrzanog izlaganja, a tijekom prirodnog izlaganja pigmenti su povećali stabilnost boje uzoraka drva obraĊenih premazima s ZnO nanoĉesticama. Dodatak TiO2 i ZnO nanoĉestica u poliakrilatni vodeni premaz nije smanjio kemijske promjene sustava toplinski modificirano drvo premaz tijekom prirodnog i ubrzanog izlaganja, dok su se kemijske promjene smanjile kombinacijom pigmenata i nanoĉestica TiO2 i ZnO. Ekstraktivne tvari pridonijele su većoj promjeni boje toplinski modificiranog drva na višoj temperaturi (212 C) tijekom ubrzanog izlaganja, što je vidljivo i na promjeni vrpce na 1595 cm-1.
Abstract (english) Thermally modified wood protected by a transparent coating is still susceptible to surface degradation due to influence of environmental factors. In this paper, the possibility of increasing the durability of transparent coating on thermally modified wood by adding TiO2 and ZnO nanoparticles in waterborne polyacrylate coating was analysed. Unmodified and thermally modified beech wood samples uncoated and coated with nine waterborne polyacrylate coatings were exposed to environmental influences. Measurements of color, gloss, cracking, peeling and mildew, mechanical and thermal properties, coatings transmittance and chemical changes were conducted.This study showed that the thermal modification beech reduced density, increased acidity, markedly reduced the polar component of surface free energy, increased the content of lignin, water and solvent extract. Addition of ZnO nanoparticles had a greater impact on the properties of waterborne polyacrylate coating than TiO2 nanoparticles. Addition of ZnO nanoparticles increased the viscosity and pH of coating. TiO2 and ZnO nanoparticles increased strength, modulus of elasticity and glass transition temperature, and reduced stretching of waterborne polyacrylate coating. Addition of TiO2 and ZnO nanoparticles in waterborne polyacrylate coating reduced colour change of thermally modified wood - coating system during natural and accelerated exposure, but it was still very pronounced and clearly visible to the naked eye. Better stabilization effect of colour change was achieved with TiO2 nanoparticles and with increasing the concentration of nanoparticles. Pretreatment of thermally modified beech wood with HALS compounds did not protect thermally modified beech wood against colour change during natural and accelerated exposure. Adding of pigments in coatings with TiO2 and ZnO nanoparticles stabilised colour of thermally modified beech wood during accelerated exposure the most and during natural exposure pigments increased colour stability of wood samples coated with coating with ZnO nanoparticles. Addition of TiO2 and ZnO nanoparticles in waterborne polyacrylate coating did not reduce chemical changes of thermally modified wood coating system during natural and accelerated exposure, while the chemical changes were reduced with combination of pigments and TiO2 and ZnO nanoparticles. Extractives contributed to the higher colour change of thermally modified wood at a higher temperature (212 C) during accelerated exposure, which was also visible in change of peak at 1595 cm-1.
Keywords
toplinski modificirano drvo
titanijev dioksid
cinkov oksid
nanoĉestice
poliakrilatni premaz
razgradnja drva
Keywords (english)
thermally modified wood
titan dioxide
zinc oxide
nanoparticles
polyacrylate coating
wood degradation
Language croatian URN:NBN urn:nbn:hr:108:653168 Study programme Title: POSTGRADUATE UNIVERSITY DOCTORAL STUDY PROGRAMME OF WOOD TECHNOLOGY Type of resource Text Extent 185 File origin Born digital Access conditions Open access Terms of use Created on 2017-01-13 14:17:02
