diplomsko delo univerzitetnega študijskega programa
Nina Trupej (Avtor), Željko Knez (Mentor), Mojca Škerget (Komentor)

Povzetek

Namen diplomskega dela je preučevanje termodinamskih lastnosti sistema polietilen glikol (PEG)/ogljikov dioksid (CO2) in primerjava dveh metod, s katerima lahko pridobimo difuzijske koeficiente v sistemu polimer/CO2. Zanima nas obnašanje PEG različnih molekulskih mas (razpon molekulskih mas od 1 000 g/mol do 100 000 g/mol) in primerjava obnašanja med njimi. Analizirana je bila topnost in difuzivnost binarnega sistema CO2 v PEG in sprememba volumna vzorca. V ta namen smo preučevali vse vzorce pri izotermnih pogojih in enakem razponu tlakov z namenom, da smo zagotovili primerljivost. Predhodno smo z metodo diferenčna dinamična kalorimetrija (DSC) določili temperature tališč PEG različnih molekulskih mas in določili temperaturo 70 °C kot delovno temperaturo obeh metod, pri kateri so vsi polimeri staljeni. Obe metodi, ki sta se izvajali, sta gravimetrični. Ena od teh so eksperimenti v avtoklavu, druga se je izvajala s pomočjo magnetne suspenzijske tehtnice (MSB). MSB je z enim samim vzorcem opravila celotno območje tlakov, ki so nas zanimali (imenovano »step-by-step« metoda). Računalniški program MessPro je pod zahtevami, katere smo vnesli, zapisoval čas, število meritev, spremembe v masi itd. do vzpostavljenega ravnotežja in sproti izrisoval graf. Sklepali smo, da se je ravnotežje meritve pri določenem tlaku vzpostavilo po osemdesetih minutah. Meritve smo preračunali v programu MS Excel v želene termodinamske lastnosti. Vzorec smo po opravljenem eksperimentu tudi slikali; celica MSB to omogoča, saj ima dve stekleni okenci, skozi kateri smo zasledovali vizualne spremembe. S programom ImageJ smo nato določili še volumen vzorca. Prej opisano metodo smo primerjali z metodo z avtoklavom, kjer smo izpostavljali vzorec različnim tlakom pri temperaturi 70 °C približno en dan in za vsako meritev uporabili svež vzorec. Razpon tlaka v avtoklavu smo nato znižali do atmosferskega in kiveto z vzorcem postavili na tehtnico ter zapisovali spremembo mase. Podatke smo s programom MS Excel preračunali v želene količine. Glavne ugotovitve diplomskega dela so: Topnost ogljikovega dioksida v PEG pada z naraščajočo molekulsko maso polimera. Difuzijski koeficient ne kaže velike odvisnosti od molekulske mase. Podobno kot pri topnosti smo ugotovili, da je sprememba volumna oz. nabrekanje vzorca manjše pri polimerih z večjo molekulsko maso. Na podlagi primerjav meritev smo ugotovili, da obe gravimetrični metodi, ki sta se uporabljali, kažeta na enak trend poteka difuzijskega koeficienta, vendar so vrednosti v primeru MSB nekoliko višje (približno za 10-1 oz. za 10-krat), kar glede na natančnost in možnost ponovljivosti pri MSB niti ni tako veliko.

Ključne besede

termodinamske lastnosti;difuzivnost;magnetna sustenzijska tehtnica;avtoklav;

Podatki

Jezik: Slovenski jezik
Leto izida:
Izvor: Maribor
Tipologija: 2.11 - Diplomsko delo
Organizacija: UM FKKT - Fakulteta za kemijo in kemijsko tehnologijo
Založnik: [N. Trupej]
UDK: 678:544.32(043.2)
COBISS: 16704022 Povezava se bo odprla v novem oknu
Št. ogledov: 3655
Št. prenosov: 316
Ocena: 0 (0 glasov)
Metapodatki: JSON JSON-RDF JSON-LD TURTLE N-TRIPLES XML RDFA MICRODATA DC-XML DC-RDF RDF

Ostali podatki

Sekundarni jezik: Angleški jezik
Sekundarni naslov: Thermodynamic properties of system polyethylene glycol (PEG)/carbon dioxide (CO[sub]2)
Sekundarni povzetek: In the present diploma thesis the thermodynamic properties of the system polyethylene glycol/carbon dioxide have been researched and two methods for determing the solubility and diffusion coefficient in the polymer/CO2 system have been compared. We are interested in the behaviour of PEGs with different molecular weights (ranging from 1,000 g/mol do 100,000 g/mol) and in the comparison of their behaviour. The solubility and the diffusivity of the binary system CO2 in PEGs, as well as the volume variation of the sample were analysed. For this purpose, all the samples were analysed at isothermal conditions and in the same pressure range, so that comparison is possible. First the melting points of the PEGs with different molecular weights were determined by means of the DSC method. For both methods 70 °C was take as the working temperature, because all polymers are in the liquid state at this temperature. Both methods used are gravimetric methods. Autoclave experiments represent one of the methods, while the other method involves measurements with magnetic suspension balance (MSB). Using a single sample, the MSB measures the whole range of pressures we are interested in (this is the “step-by-step method”). The computer programme MessPro was applied to record the time, number of measurements, changes in weight, etc. until equilibrium is reached. Simultaneously, the programme draws a graph. It was assumed that equilibrium is reached at a certain pressure after eighty minutes. The measurements can be calculated in MS Excel to obtain thermodynamic properties (solubility, diffusivity). At the end of the experiment the sample was photographed: the MSB cell is equised with two glass windows through which the changes in the sample can be monitored visually. The volume of the sample was determined using the programme ImageJ. The formerly described method was compared with the autoclave method, where the sample was exposed to different pressures at 70 °C for approximately one day. A fresh sample was used for each measurement. The pressure range in the autoclave was then lowered to the atmospheric level and the sample in the sample container was immediately put on a scale and weighted. The data were calculated with MS Excel. The main findings of the diploma thesis are: The solubility of carbon dioxide in PEG decreases with the increasing molecular weight of the polymer. The diffusion coefficient is not largely dependent on molecular weight. Similarly, it was found that the volume variation of the polymer sample was smaller with a higher molecular weight. By comparing the measurements, it can be observed that both gravimetric methods used show the same trend regarding the course of the diffusion coefficient, although the values are somewhat higher (approximately ten times) when using the MSB method. The disagreement is not regarding the accuracy ob MSB method so large.
Sekundarne ključne besede: PEG;diffusivity;solubility;magnetic suspension balance;avtoclave;
URN: URN:SI:UM:
Vrsta dela (COBISS): Diplomsko delo
Komentar na gradivo: Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo
Strani: XV, 79 str.
Ključne besede (UDK): applied sciences;medicine;technology;uporabne znanosti;medicina;tehnika;various industries;trades and crafts;razne industrije;obrti in rokodelstva;industries based on macromolecular materials;rubber industry;plastics industry;industrija makromolekulskih snovi;industrija kavčuka;industrija umetnih snovi;mathematics;natural sciences;naravoslovne vede;matematika;chemistry;crystallography;mineralogy;kemija;physical chemistry;fizikalna kemija;chemical thermodynamics;
ID: 992977