doktorska disertacija
Doroteja Vnučec (Author), Andreja Goršek (Mentor), Andreja Kutnar (Co-mentor)

Abstract

Namen doktorske disertacije je bil razvoj inovativne metode modifikacije sojinih proteinov kot osnove za izdelavo sojinega lepila, ki lahko kvalitetno zlepi različne lesne vrste in je sposobno poleg naravnega lesa lepiti tudi zgoščen les. Raziskavo smo razdelili v tri sklope. V prvem sklopu smo preučevali vpliv temperature termične modifikacije izolata sojinih proteinov (SPI) ter vpliv pH vrednosti in temperature priprave disperzije na lastnosti lepila ter na lastnosti in kvaliteto lepilnih spojev preizkušancev iz bukovine. V drugem sklopu smo preučevali uporabnost lepil na različnih materialih, in sicer na zgoščeni bambusovini in bukovini. Za pet najboljših formulacij, ki smo jih določili v prvem sklopu raziskave, smo določili kvaliteto zlepljenosti za zgoščeno in kontrolno bambusovino in bukovino. Naraven les smo termo-hidro-mehansko (THM) zgostili s postopkom viskoelastične toplotne zgostitve (VTC). Preučili smo lastnosti zgoščenih in kontrolnih površin ter lastnosti in kvaliteto lepilnih spojev. V tretjem sklopu raziskave smo optimirali masni delež SPI v lepilu za najboljšo formulacijo, ki smo jo izbrali v prvem sklopu raziskave, ter temperaturo in čas stiskanja pri vročem lepljenju. Optimiranje procesnih parametrov je potekalo na osnovi lastnosti lepil in lepilnih spojev ter kvalitete lepilnih spojev preizkušancev iz bukovine po standardih SIST EN 204 in 205. Lastnosti lepil smo določali z merjenjem viskoznosti ter lastnosti površin s preučevanjem kontaktnih kotov kaplje vode. Lastnosti lepilnih spojev smo opredelili z določanjem efektivne penetracije lepila na podlagi mikroskopskega preučevanja lepilnih spojev. Kvaliteto lepilnih spojev smo ugotavljali z merjenjem natezno strižne trdnosti preizkušancev. Rezultati vpliva temperature termične modifikacije na lastnosti lepila in lepilnih spojev ter kvaliteto zlepljenosti so pokazali, da je primerna temperatura termične modifikacije v kombinaciji s pravilno izbranimi pogoji priprave disperzije pomembno izboljšala disperzibilnost SPI in viskoznost lepila, povečala zmožnost penetracije lepila v porozno strukturo lesa, ter pomembno izboljšala trdnost lepilnih spojev, predvsem trdnost po namakanju v vodi. Preučevanje lastnosti zgoščenih in kontrolnih površin je pokazalo, da so se le te pri postopku zgostitve spremenile. Zgoščen les je imel nižjo vlažnost od kontrolnega lesa, a je kljub temu počasneje absorbiral vodo, kar kaže na večjo hidrofobnost površine. Zgostitev lesa je zmanjšala volumen praznih prostorov v lesu in posledično penetracijo lepila. Kljub temu pa so rezultati natezno strižne trdnosti pokazali, da so lepila sposobna zlepiti obe površini, tako površino zgoščenega kot naravnega lesa, ter različne lesne vrste, bambusovino in bukovino. Pri lepljenju bukovine, tako zgoščene kot kontrolne, so testirana lepila izkazala opazno višje vrednosti natezno strižne trdnosti kot pri lepljenju bambusovine. Optimiranje masnega deleža termično modificiranega SPI je pokazalo velik vpliv vsebnosti suhe snovi v lepilu na viskoznost lepila, na efektivno penetracijo ter na natezno strižno trdnost preizkušancev po namakanju v vodi. Tudi rezultati optimiranja temperature in časa lepljenja so pokazali velik vpliv natezno strižne trdnosti na vodoodpornost lepila. Lepilo z optimalnim masnim deležem SPI, s katerim smo lepili pri optimalni temperaturi in času stiskanja, smo uvrstili v D3 trajnostni razred po standardu SIST EN 204, kar pomeni, da je lepilo primerno za notranjo uporabo v prostorih s povišano vlago in za zunanjo uporabo v pokritih prostorih. Ti rezultati so potrdili veljavnost domneve, da lahko primerna metoda modifikacije SPI pomembno izboljša kvaliteto lepila in pripomore k uspešnosti razvoja bio-lepil za uporabo v lesni industriji.

Keywords

bio-lepilo;termična modifikacija;sojini proteini;sojino lepilo;lepljenje lesa;zgoščen les;

Data

Language: Slovenian
Year of publishing:
Typology: 2.08 - Doctoral Dissertation
Organization: UM FKKT - Faculty of Chemistry and Chemical Engineering
Publisher: [D. Vnučec Paušner]
UDC: 665.93:674.028.9(043.3)
COBISS: 22463747 Link will open in a new window
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Other data

Secondary language: English
Secondary title: The use of thermally modified proteins for bio-adhesives
Secondary abstract: The aim of the doctoral dissertation is the development of an innovative method of modifying soy proteins as a base for producing soy adhesive that is able of good adhesive bonding of different wood species and is capable of adhesion with natural wood as well as densified wood. The research was divided into three parts. In the first part, the influence of the thermal modification temperature of soy protein isolate (SPI) and the effects of the pH value and dispersion preparation temperature on the adhesive and bondline properties, and bondline quality of beech wood specimens was studied. In the second part, the adhesives were tested if suitable for bonding with different materials, namely bamboo and beech wood. The bondability/glueability of the densified and control bamboo and beech wood was tested when bonding with five best formulations from the first part of the dissertation. The natural wood was thermo-hydro-mechanically (THM) densified with viscoelastic thermal compression (VTC) process. The surface properties of the densified and control wood and the properties and quality of the bondlines were examined. In the third part, the mass fraction of SPI in the adhesive for the best formulation chosen in the first part, and the pressing temperature and time in the adhesion process were optimized. Optimization of the process parameters was based on the adhesive properties, bondline properties and quality of the beech wood assemblies in accordance with the standards EN 204 and 205. The properties of the adhesives were determined by measuring the viscosity and the surface properties by studying the sessile drop contact angles of water. The properties of the adhesive bondlines were determined by calculating the effective penetrations based on the microscopic examination of the bondlines. The quality of the bondlines was determined by measuring the tensile shear strength of bonded assemblies. The results obtained when studying the influence of the thermal modification temperature on the adhesive and bondline properties and bonding quality showed that the appropriate temperature of thermal modification in combination with the proper conditions of dispersion preparation, significantly improved the SPI dispersibility and adhesive viscosity, increased the adhesive penetration into the porous wood structure and significantly improved the adhesive bonding strength, especially after water soaking. The results of the surface properties of densified and control wood showed, that THM densification changed the surface properties of wood. Although the densified wood showed lower moisture content than control wood, it absorbed the water slower than control wood, indicating a more hydrophobic surface. Densification of the wood reduced the volume of the void areas in the wood causing lower adhesive penetration. Nevertheless, the results of the tensile shear strength showed that adhesives were able to bond both surfaces, the surfaces of the densified and control wood, and different wood species, bamboo and beech. When bonding the beech wood assemblies, the densified and control ones, the adhesives showed a noticeably higher tensile shear strengths than with bamboo bonding. Optimizing the mass fraction of thermally modified SPI showed great influence of the adhesive solid content on the adhesive viscosity, effective penetration and tensile shear strength of the bonded assemblies after water soaking. The results of the optimization of the pressing temperature and time showed great influence of the tensile shear strength on the adhesive water resistance. The adhesive with optimal SPI mass fraction has fulfilled the conditions for durability class D3 according to standard EN 204, when bonding was performed at optimal pressing temperature and time. D3 adhesive is suitable for interior use exposed to high humidity and exterior use not exposed to weather. These results confirmed the validity of the assumption that the appropriate method of modifying SPI
Secondary keywords: thermal modification;soy protein;soy adhesive;bio-adhesive;wood adhesion;wood densification;Lepila;Disertacije;
Type (COBISS): Doctoral dissertation
Thesis comment: Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo
Pages: XVI, 96 str.
ID: 11259691