Utjecaj ugljikovih nanocjevčica na svojstva poliamida

master's thesis

• Title (english): Influence of carbon nanotubes on polyamide properties
• Author: Nicol Šorgo
• 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: 2018-09-28, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering; Chemical Engineering in Material Development

Abstract

Polimerni nanokompoziti područje su brojnih istraživanja zbog svojih poboljšanih svojstava u odnosu na klasične polimerne materijale i kompozite što im omogućuje široku primjenu. Takva svojstva im omogućuju nanopunila koja zbog svojih dimenzija i strukture sama posjeduju izvanredna svojstva. U ovom radu provedena su istraživanja utjecaja dodatka ugljikovih nanocjevčica (MWCNT) i modificiranih ugljikovih nanocjevčica (MWCNT-COOH) masenih udjela u rasponu od 0,5 % do 5 % u poliamidnu matricu (PA). Uzorci PA i nanokompozita pripremljeni su postupkom iz taline. Zamiješani su u Brabender gnjetilici te potom prešani na laboratorijskoj hidrauličkoj preši. U svrhu analize toplinskih, mehaničkih i električnih svojstava PA/MWCNT i PA/MWCNT-COOH nanokompozita, provedena je karakterizacija uzoraka diferencijalnom pretražnom kalorimetrijom (DSC), termogravimetrijskom analizom (TGA), THB metodom određivanja toplinske vodljivosti, testom jednoosnom istezanja te elektrokemijskom impedancijskom spektroskopijom (EIS). Rezultati DSC analize pokazali su da ugljikove nanocjevčice (MWCNT) djeluju kao nukleacijski centri i ubrzavaju kristalizaciju PA matrice, ali ne utječu na uređenost kristalne strukture. Zbog polarne prirode površine i bolje dispergiranosti, MWCNT-COOH punila znatnije ubrzavaju kristalizaciju PA u odnosu na MWCNT. Iako ugljikove nanocjevčice imaju nukleacijski učinak, zbog njihove prisutnosti lanci PA imaju ograničen prostor za gibanje što ometa proces kristalizacije matrice. Toplinska stabilnost PA matrice se povećava dodatkom oba punila MWCNT i MWCNT-COOH te se početak razgradnje pomiče na više temperature. Veća se toplinska vodljivost postiže dodatkom punila MWCNT-COOH u odnosu na dodatak MWCNT. Ovakvi rezultati pripisuju se dobroj toplinskoj vodljivost MWCNT. Rezultati testa jednoosnog istezanja su pokazali da se dodatkom obje vrste MWCNT punila u PA matricu, smanjuje modul elastičnosti i čvrstoća u točki popuštanja te se povećava istezanje u točki popuštanja. Ovakvo ponašanje može se pripisati učinku MWCNT punila koje djeluje na PA tako što smanjuje udio matrice koji može kristalizirati što utječe na smanjenje modula i čvrstoće te povećanje deformabilosti nanokompozitnih sustava. Rezultati ispitivanja električne vodljivosti nanokompozita EIS metodom pokazuju jednake vrijednosti impendacije (otpora) kao i čista PA matrica.

Abstract (english)

Polymer nanocomposites are a field of numerous researches due to their improved properties compared to conventional polymeric materials and composites which enables them to be widely used. Nanofillers possesses remarkable properties because of their dimensions and structure which enabels them improve the properties of the nanocomosites. In this study the addition of carbon nanotubes (MWCNT) and modified carbon nanotubes (MWCNT-COOH) in the range of 0.5 wt. % to 5 wt. % in the polyamide matrix (PA) was investigated. PA and nanocomposite samples were prepared by melt mixing in a Brabender plasticoder and then pressed on a laboratory hydraulic press. For the purpose of analyzing the thermal, mechanical and electrical properties of PA/MWCNT and PA/MWCNT-COOH nanocomposites, the samples were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), THB thermal conductivity determination method, tensile test and electrochemical impedance spectroscopy (EIS). Results of DSC analysis showed that carbon nanotubes (MWCNTs) act as nucleation centers and accelerate the crystallization of PA matrix, but do not affect the order of the crystal structure. Due to the polar nature of the surface and the better dispersion, MWCNT-COOH fillers more significantly accelerate the PA crystallization compared to MWCNT. Although the carbon nanotubes have a nucleation effect, due to their presence the PA chains have limited motion space which interferes with the crystallization process of the matrix. The thermal stability of the PA matrix increases with the addition of both MWCNT and MWCNTCOOH fillers, and the start of decomposition moves to higher temperatures. The higher thermal conductivity is achieved by the addition of MWCNT-COOH filler compared to the addition of MWCNT. Such results are attributed to the good thermal conductivity of MWCNT. The results of the tensile test showed that by adding both types of MWCNT fillers in the PA matrix, the modulus of elasticity and the yield stress are reduced, but the yield strain increases. This behavior can be attributed to the effect of MWCNT fillers on PA which reduces the fraction of the matrix that can crystallize, which then affects the reduction of the modulus and yield strength and increases the deformability of the nanocomposite systems. The results of the EIS method of the electrical conductivity of the nanocomposites show equal impendance (resistance) as the pure PA matrix.

• Keywords: PA/MWCNT; PA/MWCNT-COOH; toplinska svojstva; toplinska stabilnost; toplinska vodljivost; mehanička svojstva; električna vodljivost
• Keywords (english): PA/MWCNT; PA/MWCNT-COOH; thermal properties; thermal stability; thermal conductivity; mechanical properties; electrical conductivity
• Language: croatian
• URN:NBN: urn:nbn:hr:149:655697
• 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: Closed access
• Created on: 2020-10-30 12:08:37