Utjecaj modifikacije višestijenih ugljikovih nanocjevčica na svojstva poliuretana

master's thesis

• Title (english): Influence of carbon nanotube modification on polyurethane properties
• Author: Martina Zeljko
• Mentor: Sanja Lučić Blagojević (mentor)
• Committee member: Sanja Lučić Blagojević (predsjednik povjerenstva)
• Committee member: Mirela Leskovac (član povjerenstva)
• Committee member: Domagoj Vrsaljko (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2016-09-27, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering; Chemical Engineering in Material Development

Abstract

U ovom radu prvo su karakterizirane višestijene ugljikove nanocjevčice (MWCNT) te MWCNT modificiranih –COOH skupinama. Karakterizacija MWCNT, MWCNT-COOH provedena je Ramanovom spektroskopijom, termogravimetrijskom analizom, zatim pomoću pretražne elektronske mikroskopije, mjerenjem kontaktnog kuta, te određivanjem disperzivnosti u različitim otapalima. Zatim je istraživan učinak dodatka MWCNT te MWCNT–COOH u rasponu udjela od 0-4% mas. na svojstva poliuretana. Uzorci nanokompozita pripravljani su postupkom iz otopine poliuretana u acetonu te polaganim sušenjem otopina na sobnoj temperaturi. Učinak dodatka nanopunila na sferolitnu strukturu poliuretana te raspodjeljenost nanopunila u PU matrici anlizirana je optičkom polarizacijskom mikroskopijom. Toplinska svojstva u neizotermnim i izotermnim uvjetima istraživana su diferencijalnom pretražnom kalorimetrijom (DSC), a toplinska stabilnost termogravimetrijskom analizom (TGA). Električna provodnost uzoraka određivana je metodom četiri kontakta. Utjecaj dodatka punila na mehanička svojstva PU kompozita ispitana je testom jednoosnog istezanja. Ramanova spektroskopija pokazala je da MWCNT imaju veći udio nečistoća nego MWCNT-COOH. TGA analiza pokazala je da su MWCNT-COOH toplinski stabilnije od MWCNT. Rezultati SEM analize pokazali su da funkcionalizacija ne utječe na stupanj agregacije. Rezultati kontaktni kuteva ukazuju da se funkcionalizacijom s -COOH skupinom uvelike mijenja polarnost nanocijevčica. Rezultati određivanja disperzivnosti pokazali su da su obe vrste nanocjevčica jako dobro dispergirane u acetonu. Optička polarizacijska mikroskopija pokazala je da dodatak oba punila razrušava krupnu sferolitnu morfologiju poliuretana. Uočeno je da su na makrorazini modificirane MWCNT-COOH bolje dispergirane u masi uzorka nego čiste MWCNT. DSC rezultati pokazali su da u neizotermnim uvjetima do određenog udjela dodatak obje vrste MWCNT ubrzavaju kristalizaciju mekog segmenta poliuretana. U uvjetima izotermne kristalizacije MWCNT također znatnije ubrzavaju kristalizaciju nego MWCNT-COOH. Rezultati termogravimetrijske analize upućuju da se dodatkom obje vrste MWCNT znatno poboljšava toplinska stabilnost u čitavom rasponu udjela nanopunila. Rezultati vodljivosti pokazali su da se i dodatakom malih udjela MWCNT vodljivost znatno povećava. Rezultati ispitivanja mehanički svojstava nanokompozita ukazuju da dodatak obje vrste MWCNT punila snižava prekidnu čvrstoću i prekidno istezanje kompozita.

Abstract (english)

In this study carbon nanotubes (MWCNTs) and MWCNTs modified with COOH groups were characterized. Characterization of MWCNTs, MWCNTs-COOH was performed by Raman spectroscopy, thermal analysis, then using scanning electron microscopy, by measuring the contact angle, and determining dispersibility in various solvents. After that the effect of the addition of MWCNTs and MWCNTs-COOH in range of 0-4% wt. on the properties of polyurethane were investigated. Samples of nanocomposite were prepared from solution of polyurethane in acetone and slowly drying the solution at room temperature. The effect of the addition of nanofiller on spherulite structure of polyurethane and distribution nanofiller in PU matrix were analyzed by optical polarization microscopy. Thermal properties in the non-isothermal and isothermal conditions were investigated by differential scanning calorimetry (DSC) and thermal stability by thermogravimetric analysis (TGA). The electrical conductivity of the samples was determined using four probe method. Effect of the addition of fillers on the mechanical properties of PU nanocomposites was examined by uniaxial deformation test. Raman spectroscopy showed that MWCNTs have a higher proportion of impurities than MWCNTs-COOH. TGA analysis showed that MWCNTs-COOH are more thermally stable than MWCNTs. The results of SEM analysis showed that the functionalization does not affect the degree of aggregation. The results of the contact angles indicate that the functionalization by COOH groups significantly changes the polarity of the nanotubes. The results of determining dispersibility showed that both types of nanotubes are very well dispersed in the acetone. Optical polarization microscopy showed that the addition of both nanofillers disrupts the spherulite morphology of polyurethane. It was noted that at the macro level modified MWCNTs-COOH are better distributed in the the sample than pure MWCNTs. DSC results showed that in the non-isothermal conditions up to the addition of a certain amount of both types of MWCNTs accelerate the crystallization of the soft segments of polyurethane. In terms of isothermal crystallization MWCNTs also significantly accelerate crystallization than MWCNTs-COOH. The results of thermogravimetric analysis indicate that the addition of both types of MWCNTs significantly improves the thermal stability. Conductivity results showed that the the addition of small amount of MWCNTs significantly increases the conductivity. The results of the mechanical properties of the nanocomposite show that addition of both types of fillers MWCNTs reduced tensile strength and elongation of the composite.

• Keywords: PU/MWCNT; PU/MWCNT-COOH; morfologija; kristalnost; toplinska svojstva; električna svojstva; mehanička svojstva
• Keywords (english): PU/MWCNT; PU/MWCNT-COOH; morphology; crystallinity; thermal properties; electrical properties; mechanical properties
• Language: croatian
• URN:NBN: urn:nbn:hr:149:427969
• Study programme: Title: Materials Science and Engineering - Graduate study; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka kemijskog inženjerstva (magistar/magistra inženjer/inženjerka kemijskog inženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2017-10-19 08:56:33