doktorska disertacija
Silvo Hribernik (Author), Majda Sfiligoj-Smole (Mentor), Karin Stana-Kleinschek (Co-mentor), Janko Jamnik (Co-mentor)

Abstract

Cilj naloge ććŠtudij predobdelave in oplaščanja regeneriranih celuloznih vlaken z nano delcićć je razvoj postopkov za oplaščanje celuloznih vlaken s funkcionalnimi nano delci, ki bi obstoječemu naboru lastnosti teh materialov dodali nove. Uporabili smo viskozna vlakna, ki smo jih oplaščali z delci silicijevega dioksida (SiO2) in železovega oksida-magnetita (Fe3O4). Raziskavaje bila razdeljena v tri dele; predobdelava viskoznih vlaken z namenom aktivacije njihove površine ter povečanja pornega sistema s čimer izboljšamo adhezijo delcev in omogočimo njihovo rast v notranjosti vlaken. V drugem delu smo raziskali sintezo delcev magnetita ter lastnosti nastalih delcev; sintezne postopke smo primerjali z vidika njihove primernosti v kombinaciji s celuloznimi substrati. Tretji del je zajemal oplaščanje vlaken z delci silicijevega dioksida in magnetita po različnih postopkih. Z nabrekanjem v vodnih raztopinah natrijevega hidroksida različnih koncentracij smo odprli strukturo vlaken, s postopki sušenja z zamrzovanjem (liofilizacija) pa smo to povečanje pornega sistema ohranili, v primerjavi s sušenjem na zraku ali pri povišanih temperaturah. Raziskali smo vpliv postopkov predobdelav na nadmolekulsko strukturo vlaken, povečanje njihovega pornega sistema, na elektrokinetične lastnosti (površinski potencial) ter mehanske lastnosti. Povečanje deleža por je odvisno od uporabljene koncentracije natrijevega hidroksida in postopka zamrzovanja; višje koncentracije so v tem pogledu bolj učinkovite, vendar povzročajo znatnejše poslabšanje mehanskih lastnosti vlaken. Za nadaljnje postopke oplaščanja smo uporabili vlakna, nabrekana v 5 ut.% NaOH, ki smo jih počasi zamrzovali in liofilizirali. Podrobna raziskava sinteze delcev magnetita je zajemala variiranje molarnih koncentracij raztopin prekurzorjev ter njihovih razmerij, ter načina dodajanja komponent v reakcijski sistem. Spremljanje poteka reakcij in nastanka magnetita v posameznih fazah dodajanja reagentov oz. v določenih pH področjih ter analiza magnetnih lastnosti nastalih delcev je bilaosnova za izbiro postopkov za kasnejše oplaščanje celuloznih vlaken. Koloidne lastnosti pripravljenih disperzij magnetita so bile raziskane s stališča njihove elektroforetične mobilnosti in velikosti delcev. Oplaščanje regeneriranih celuloznih vlaken z nano delci je potekalo po postopku in situ formacije delcev na površini vlaken za oba sistema delcev ter v primeru magnetita tudi z adsorpcijo delcev iz predhodno pripravljene disperzije. Aktivirana površina liofiliziranih vlaken diktira nastanek homogenih in gostejših plasti nano delcev v primerjavi z neenakomerno pokritimi površinami in aglomerati na zraku sušenih vlaken oz. vlaken brez predhodnega nabrekanja. Postopek liofilizacije pa omogoča v primeru delcev silicijevega oksida tudi njihovo rast v notranjosti vlaken. Lastnosti pripravljenih kompozitnih vlaken (viskozna vlakna z nano delci), ki so posledica anorganske faze, so v veliki meri izrazitejše v primeru liofiliziranih vlaken; stopnja zaščite proti vnetju vlaken in posledičnem temperaturnem razpadu, ki jo dajejo delci silicijevega dioksida ter vrednosti nasičene magnetizacije, ki jo prispevajo delci magnetita so višje pri vlaknih, ki smo jih pred nanosom delcev liofilizirali.

Keywords

regenerirana celulozna vlakna;alkalna preobdelava;nabrekanje;sušenje;liofilizacija;elektrokinetične lastnosti;nano delci;sinteza delcev;oplaščenje vlaken;

Data

Language: Slovenian
Year of publishing:
Source: [Maribor
Typology: 2.08 - Doctoral Dissertation
Organization: UM FS - Faculty of Mechanical Engineering
Publisher: S. Hribernik]
UDC: 677.463.017:544.722.12(043.3)
COBISS: 252288256 Link will open in a new window
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Other data

Secondary language: English
Secondary title: STUDY OF PRE-TREATMENT AND COATING OF REGENERATED CELLULOSE FIBRES WITH NANO PARTICLES
Secondary abstract: Aim of the presented thesis is a development of procedures for coating of regenerated cellulose fibres with functional nano particles, which can add new properties to these fibres. We have used viscose fibres, which were coated with silicon dioxide particles (SiO2) and iron oxide-magnetite particles (Fe3O4). Research work was divided into three parts; pre-treatment of viscose fibres with an aim to activate their surface and to enlarge their pore system, which would enhance the adhesion of particles to the fibres surface and allow them to also grow in the inside of fibres. Second part is concerned with the magnetite particlesć synthesis and their properties; synthesis procedures were compared from the viewpoint of their suitability to be combined with cellulose fibres. Third part deals with the coating of fibres with silicon dioxide and iron oxide-magnetite particles with different procedures. Swelling of fibres in aqueous solutions of sodium hydroxide opens their fibrillar structure, while freezing and freeze-drying retains this enlargement of the pore system, in contrast with conventional air or elevated temperature drying. Effect of different pre-treatment procedures on fibresć supramolecular structure, enlargement of their pore system, surface potential and mechanical properties was investigated. Degree of enhancement of the pore system depends on the used concentration of sodium hydroxide and type of freezing; higher alkali concentrations are more effective, but at a cost of extensive decrease of mechanical propertiesć values. For coating with nano particles, fibres, swollen in 5 w.% NaOH and slowly frozen prior to freeze-drying, were used. Analysis of magnetite particlesć synthesis comprisedof variations of molar concentrations of precursor solutions as well as different addition protocols of reactants into the reaction system. Following the synthesis and evolution of particlesć formation in different stages of synthesis procedure i.e. at different pH values and analysis of particles properties was basis for choosing the synthesis routes for subsequent coatings of fibres. Colloidal properties of prepared dispersions were investigated from a viewpoint of particlesć electrophoretic mobility and their sizes. Coating of fibres was carried out with an in situ formation of particles in presence of fibres and in the case of magnetite, also with an adsorption of particles from a pre-prepared dispersion. Activated surface of viscose fibres dictates the formation of surface layers of particles; homogenous and densely packed layers are formed, while air-dried fibres exhibit unevenly covered surfaces and aggregates of particles. Freeze-dried fibres also enable, in the case of silicon dioxide, their growth in the interior of fibres. Properties of prepared composite fibres (viscose fibres with nano particles), which result from the presence of inorganic phase, are more pronounced with freeze-drying pre-treatment; degree of combustion prevention and subsequent temperature degradation, which is yielded with silica particles and saturation magnetization values, contributed by magnetite particles.
Secondary keywords: Celulozna vlakna;Disertacije;Obdelava;
URN: URN:SI:UM:
Type (COBISS): Dissertation
Thesis comment: Univ. Maribor, Fak. za strojništvo
Pages: VII, 171 f.
Keywords (UDC): applied sciences;medicine;technology;uporabne znanosti;medicina;tehnika;various industries;trades and crafts;razne industrije;obrti in rokodelstva;textile industry;tekstilna industrija;man-made fibres;umetna vlakna;mathematics;natural sciences;naravoslovne vede;matematika;chemistry;crystallography;mineralogy;kemija;physical chemistry;fizikalna kemija;chemistry of surface phenomena and colloids;kemija površinskih pojavov in koloidov;
ID: 1012165