Združljivost lesa s kompozitom polimetilmetakrilata in aluminijevega hidroksida

Vovk, Matej (author), Šernek, Milan (mentor)

V sklopu raziskav smo proučili lastnosti kompozita iz polimetilmetakrilata in aluminijevega hidroksida (PMMA/ATH) ter ugotavljali kakšna je njegova združljivost z lesom. Površino PMMA/ATH smo obdelali z zračno plazmo z dielektrično barierno razelektritvijo. Spremembe kemijske strukture so bile analizirane z rentgensko fotoelektronsko spektroskopijo (XPS) in infrardečo spektroskopijo z oslabljenim odbojem (ATR-FTIR). S konfokalno lasersko mikroskopijo in mikroskopijo na atomsko silo smo proučili vpliv na strukturo in morfologijo površine. Rezultati so pokazali, da je obdelava s plazmo povzročila jedkanje polimerne matrice PMMA/ATH kompozita, ponovno polimerizacijo PMMA in ponovno depozicijo plasti jedkanega PMMA na površini kompozita, kar je izničilo pozitiven učinek plazme. Z meritvami proste površinske energije in preizkusi strižne trdnosti lepilnih spojev smo proučili možnost uporabe zračne plazme pri lepljenju PMMA/ATH in lesa. Nadalje smo analizirali lastnosti prahu PMMA/ATH, katerega delci so bili nepravilne oblike. Mletje prahu je povzročilo lom delcev ATH v PMMA matrici in povečanje proste površinske energije, predvsem njenega polarnega dela. Diferenčna dinamična kalorimetrija (DSC) prahu je pokazala značilen termični razpad ATH do temperature priližno 320 °C, ko je nastopila eksotermna reakcija do temperature 445 °C. Ugotovljeno je bilo, da je takšen prah primeren za izdelavo kompozitov z metodo vročega stiskanja. Površino prahu PMMA/ATH smo modificirali z ureido- in amino-funkcionalnima silanskima oprijemalnima sredstvoma. XPS analiza modificiranega prahu je pokazala prisotnost kemično vezanih silanov na površini PMMA/ATH. Z višanjem stopnje površinske modifikacije prahu se znižujejo stični koti vode s prahom, medtem ko prosta površinska energija narašča. Tako obdelan PMMA/ATH prah smo uporabili pri alternativnem pristopu izdelave lesno-plastičnega kompozita (WPC) z dodatkom lesnih delcev in melamin-urea-formaldehidnega (MUF) lepila. Mehanski testi izdelanih kompozitov so pokazali, da ima stopnja površinske modifikacije prahu značilen vpliv na modul elastičnosti in upogibno trdnost, medtem pa ni značilnih razlik med uporabljenima silanoma.

• Language: Slovenian
• Keywords: polimetilmetakrilat, aluminijev hidroksid, les, združljivost, lepljenje, adhezija, plazma, dielektrična barierna razelektritev, silan, XPS, ATR-FTIR, DSC, melamin-urea-formaldehid, lesno-plastični kompozit, SEM
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: BF - Biotechnical Faculty
• Publisher: [M. Vovk]
• Year: 2020
• PID: 20.500.12556/RUL-117656
• UDC: 678.86:621.792(043.3)
• COBISS.SI-ID: 25026307
• Publication date in RUL: 19.07.2020

Secondary language

• Language: English
• Title: Compatibility of wood with composite from poly(methyl methacrylate) and aluminium hydroxide

Abstract

Within the scope of the research, the characteristics of aluminium trihydrate-filled poly(methyl methacrylate) (PMMA/ATH) have been studied, and its compatibility with wood has been determined. The surface of PMMA/ATH has been modified with air plasma with dielectric barrier discharge. Changes of the chemical structure have been determined with x-ray photoelectron spectroscopy (XPS) and attenuated total reflection – infrared spectroscopy (ATR-FTIR). Confocal laser microscopy and atom force microscopy have been deployed to study the structure and morphology of the modified surfaces. The plasma treatments resulted in an etching of the matrix polymer, repolymerization and re-deposition of the etched PMMA material on the surface of the composite, which obliterated the positive impact of the plasma treatment. Surface free energy (SFE) measurements and adhesive bond strength tests were used to correlate the results of plasma effect to bonding PMMA/ATH with wood. Furthermore, the characteristics of PMMA/ATH powder have been analysed. Milling of the powder resulted in fracturing ATH particles in PMMA matrix and increase of SFE on account of its polar part. Differential scanning calorimetry (DSC) analysis of the powder showed a typical thermal decomposition of aluminium trihydrate up to about 320 °C, after which an exothermic reaction is observed up to 445 °C. It was concluded that PMMA/ATH powder is suitable for the production of a composite in a hot-press method. The surface of PMMA/ATH powder has been modified with ureido- and amino-functional silane coupling agents. XPS analysis of a modified powder confirmed chemically attached silanes on the surface of PMMA/ATH. With an increased surface modification rate, water contact angles decrease and the surface free energy of the modified powder increases. Modified PMMA/ATH powder was used in an alternative approach to producing wood-plastic composites (WPC) with the addition of wood particles and melamine-urea-formaldehyde resin (MUF). Mechanical tests of the composites indicate that the surface modification rate has a significant impact on the elastic modulus and modulus of rupture, while there are no significant differences between silanes used.

• Keywords: poly(methyl methacrylate), aluminium hydroxide, wood, compatibility, bonding, adhesion, plasma, dielectric barrier discharge, silane, XPS, ATR-FTIR, DSC, melamine urea formaldehyde, wood-plastic composite, SEM