Utjecaj obrade ugljikovih nanocjevčica na kinetiku kristalizacije polilaktida

master's thesis

• Title (english): Influence of carbon nanotubes modification on crystallization kinetic of polylactide
• Author: Matea Šako
• Mentor: Sanja Lučić Blagojević (mentor)
• Committee member: Sanja Lučić Blagojević (predsjednik povjerenstva)
• Committee member: Domagoj Vrsaljko (član povjerenstva)
• Committee member: Zrinka Buhin Šturlić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2015-07-16, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering; Chemical Engineering in Material Development

Abstract

U ovom radu istražen je utjecaj obrade ugljikovih nanocjevčica na kinetiku kristalizacije polilaktida. Višestjenčane ugljikove nanocjevčice modificirane su s COOH skupinama (uzorak MWCNT-COOH). Ovaj uzorak modifikacijom je preveden u MWCNT-COOC12H25. PLA/MWCNT nanokompoziti (0-5 % mas punila) pripravljeni su postupkom iz taline u Brabender gnjetilici i prešanjem granulata na preši. Kinetika izotermne kristalizacije nanokompozita istražena je tehnikom diferencijalne pretražne kalorimetrije. Rezultati su analizirani Avramijevim modelom, te je određen parametar k koji je proporcionalan gustoći nukleacije i brzini rasta kristala i parametar n koji ovisi o mehanizmu nukleacije i rastu kristala. Pomoću ovih parametara mogu se izračunati t1/2, tmax i parametar K koji je direktan pokazatelj brzine kristalizacije. Vrijednosti parametra n su između 2 i 3,3, što znači da dio kristala stvara trodimenzionalnu sferolitnu strukturu a dio dvodimenzionalnu. Vrijednosti parametra K za PLA matricu pokazuju da brzina kristalizacije raste sa porastom temperature do 100 °C, nakon čega se smanjuje. Dodatkom punila temperatura maksimalne brzine kristalizacije pomaknuta je prema nižim temperaturama. MWCNT-COOH i MWCNT-COOC12H25 ubrzavaju izotermnu kristalizaciju PLA matrice odnosno imaju nukleacijski učinak. Nukleacijski učinak ovih punila ovisi znatnije o temperaturi izotermne kristalizacije te o količini punila, a neznatno o vrsti funkcionalnih skupina graftiranih na površinu MWCNT. Najveća brzina kristalizacije PLA ostvaruje se na temperaturi 95 °C i to dodatkom 5 % mas MWCNT-COOH.

Abstract (english)

In this work, influence of carbon nanotubes modification on isothermal crystallization kinetic of polylactide was investigated. Multiwall carbon nanotubes (MWCNT) modified with -COOH group and -COOC12H25 group were used. PLA/ MWCNT nanocomposites (0-5 % wt) were prepared by melt blending procedure in Brabender plasticoder and by molding in press. Crystallization kinetic was investigated using differential scanning calorimetry. Results were analyzed according to the Avrami method and the parameters n and k were determined. Parameter k is proportional to the density of nucleation and to rate of crystal growth while parameter n depends on nucleation and crystal growth mechanisms. Using the following parameters t1/2, tmax and K that are indicators of crystallization rate are calculated and analyzed. Vales of n parameter, between 2 and 3.3 indicate that part of the crystals has three-dimensional spherulite structure and part of them two-dimensional.Values of parameter K for PLA matrix indicate that rate of crystallization increases up to 100 °C, and after that decreases. By filler addition temperature of maximal crystallization rate is shifted toward lower temperature. MWCNT-COOH and MWCNT-COOC12H25 accelerate isothermal crystallization of PLA matrix, meaning that they have nucleation effect. Nucleation effect of these fillers depends more significantly on the temperature of isothermal crystallization and on amount of added filler, and slightly on type of functional groups grafted on MWCNT's surface. The highest crystallization rate has PLA nanocomposite with 5 % wt of MWCNT-COOH at temperature 95 °C.

• Keywords: kinetika izotermne kristalizacije; Avramijev model; PLA matrica; PLA nanokompoziti s modificiranim MWCNT
• Keywords (english): isothermal crystallization rate; Avrami model; PLA matrix; PLA nanocomposites with modified MWCNT's
• Language: croatian
• URN:NBN: urn:nbn:hr:149:410303
• Study programme: Title: Chemical 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: 2016-12-22 13:37:19