diplomsko delo
Ivan Vrbnjak (Author), Mojca Škerget (Mentor), Željko Knez (Co-mentor)

Abstract

Procesiranje polimerov s CO2 z ustrezno metodo in pri ustreznih obratovalnih pogojih, daje polimerom posebne fizikalne in mehanske lastnosti, katere omogočajo njihovo uporabo v biomedicini, farmacevtski industriji, industriji praškastih premazov, tekstilni industriji… Poznavanje topnosti in difuzijskih koeficientov SC CO2 pri različnih parametrih (tlak, temperatura) je za načrtovanje teh postopkov obdelave polimerov ključnega pomena. Topnosti in difuzijske koeficiente CO2 smo določali v polimerih poli(L-laktid) (PLLA) in poli(laktid-ko-glikolid) (PLGA) ter komercialnem β-hidroksialkil amidu (β-HAA) z gravimetrično metodo. Z MSB (magnetno suspenzijsko tehtnico) smo meritve opravili pri treh različnih temperaturah (333 K, 353 K in 373 K) in tlakih do 30 MPa. Po izpostavitvi omenjenih substanc tlaku je zaradi raztapljanja plinskih molekul substanca nabreknila, to spremembo volumna smo posneli s kamero. Sliko smo obdelali v programu ImageJ, kjer smo predpostavili premer kivete kot začetno referenco, in določili volumne substanc po absorpciji CO2. Dobljene meritve z MSB smo ustrezno obdelali in popravili z upoštevanjem sprememb volumnov. Sprememba volumna je pri PLLA in PLGA rasla s povišanjem tlaka, pri β-HAA pa se je po kratkem povišanju znižala in ostala konstantna, kar pripisujemo hidrostatičnemu tlaku. Topnosti CO2 so se z zviševanjem tlaka in z zniževanjem temperature v vseh treh primerih povečevale. Difuzijski koeficienti so odvisni od koncentracije CO2 v polimeru oz. β-HAA, pri vseh substancah in pogojih na začetku strmo naraščajo, dokler ne dosežejo maksimalnih vrednosti, nato pa začnejo padati zaradi močnejšega delovanja hidrostatičnega tlaka od samega delovanja tlaka plina. Ugotovili smo, da ob izpostavitvi polimerov SC CO2, ki je dobro topilo, ni prišlo v nobenem primeru do raztapljanja polimera, ampak je polimer absorbiral CO2 in nabreknil. To smo potrdili z visokimi variacijami volumnov, topnostmi ter difuzijskimi koeficienti. SC CO2 se je izkazal kot zelo dobro sredstvo za procesiranje polimerov. SC CO2 je prav tako dobro sredstvo za procesiranje β-HAA, saj je β-HAA pokazal podobne lastnosti, ob izpostavitvi SC CO2, kot polimeri. Dosegli smo prav tako visoke vrednosti difuzijskih koeficientov in topnosti CO2, le sprememba volumna ni dosegla tako velikih vrednosti kot pri polimerih. Ta podobnost s polimeri nam omogoča, da β-HAA uporabljamo kot sredstvo za izboljšanje lastnosti polimerov.

Keywords

polimeri;zamreževalec;superkritični ogljikov dioksid;topnost;difuzivnost;magnetna suspenzijska tehtnica;

Data

Language: Slovenian
Year of publishing:
Source: Maribor
Typology: 2.11 - Undergraduate Thesis
Organization: UM FKKT - Faculty of Chemistry and Chemical Engineering
Publisher: [I. Vrbnjak]
UDC: 678:544.32(043.2)
COBISS: 13927190 Link will open in a new window
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Other data

Secondary language: English
Secondary title: Termodinamic and transport properties for polymers processing with CO2
Secondary abstract: Processing of the polymers with CO2 by the appropriate method and the corresponding operation conditions, gives to polymer specific physical and mechanical properties, which allow their use in the biomedical and pharmaceutical industry, industry of powder coatings, textile industry, etc. Knowledge of the solubility and diffusion coefficients of SC CO2 at different parameters (pressure, temperature) is crucial for the design of these procedures for the treatment of polymers. The solubility and diffusion coefficients of CO2 in the polymers poly (L-lactide) (PLLA), poly (lactide-co-glycolide) (PLGA) and a commercial β-hydroxyalkyl amide (β-HAA) have been determined using the gravimetric method. The MSB (magnetic suspension balance) measurements were performed at three different temperatures (333 K, 353 K and 373 K) and pressures up to 30 MPa. After the exposure of mentioned substances to the pressure, swelling of substances was observed due to dissolution of the gas molecules in matrix. The change in the volume was recorded by the camera. The image has been processed using the program ImageJ, where the diameter of the tubes was assumed as a starting reference, and the volume of the substance after the absorption of CO2 was determined. Measurements obtained with the MSB were corrected considering the changes in volumes. The volumes of the PLLA and PLGA increased with increasing of the pressure, but for β-HAA initial increase of the volume was observed at lower pressures, however with further increase of pressure, the volume slightly decreased again and afterwards it remained constant. We attribute this to the hydrostatic pressure. Solubility of CO2 in investigated materials increases by increasing the pressure and by lowering the temperature. Diffusion coefficients depend on the concentration of CO2 in the polymers and β-HAA; initially they increase until they reach maximum values and afterwards they start to decrease because the influence of the hydrostatic pressure is stronger than the gas pressure. We observed that when the polymer was exposed to SC CO2, which is a good solvent, the polymer was not dissolved in CO2, instead the polymer absorbed CO2 and swelled. We confirmed this with high variations of volumes, solubility and diffusion coefficient. SC CO2 has proved to be a very good medium for processing of polymers. SC CO2 is also a good tool for the processing of β-HAA because the β-HAA showed similar properties as polymers, when was exposed to SC CO2. High diffusion coefficients and solubility of CO2 in β-HAA were determined, only the volume change did not reach such high values as in polymers. This similarity with polymers allows us to use β-HAA as additive to improve the properties of polymers.
Secondary keywords: polymer;supercritical carbon dioxide;crosslinker;solubility;diffusion;magnetic suspension balance;
URN: URN:SI:UM:
Type (COBISS): Undergraduate thesis
Thesis comment: Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo
Pages: XII, 58 f.
Keywords (UDC): 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: 988066