POROUS ELASTOMERS BASED ON POLYURETHANES

V diplomski nalogi so prikazani poskusi sinteze poroznega elastomera z uporabo fotopolimerizacije. Želeli smo sintetizirati elastomer z dobrimi mehanskimi lastnostmi, saj so porozni materiali po navadi krhki. Kot monomer smo uporabili alifatski uretanski diakrilat (AUD, Sartomer CN 965), ki smo ga dodali v emulzijo z visokim deležem notranje faze. Emulzijo smo mešali eno uro v bučki potopljeni v termostatirano vodo z mešalom pri 250 obratih na minuto. Nastale emulzije smo vlili v kalupe in spolimerizirali v UV komori, nato smo produkte očistili v izopropanolu in posušili. Posušene produkte smo analizirali s pomočjo vrstičnega elektronskega mikroskopa in FTIR spektroskopijo. Pri poskusih smo spreminjali pogoje, kot so temperatura, delež notranje faze, topila in surfaktana. Rezultati so pokazali tvorbo emulzij v širokem temperaturnem območju in pri različnih deležih interne faze, vendar so se nam produkti po sušenju precej skrčili, postali trdni in neelastični in nadaljnje analize v večini primerov niso pokazale lepo porozne strukture. Z namenom izboljšanja elastičnosti in poroznosti materiala smo k AUDju dodali različna zamreževala (MBAA in EGDMA) ter eksperimente izvedli v dušikovi atmosferi, saj prisotnost kisika v reakcijski zmesi lahko moti potek polimerizacije. Testirana zamreževala so izboljšala poroznost materiala, a so bili materiali precej bolj krhki, dušikova atmosfera pa je povzročila zgolj nastanek nehomogenih emulzij, ki niso dobro spolimerizirale.The graduation thesis shows attempts to synthesize a porous elastomer by means of photopolymerization. We wanted to synthesize an elastomer with good mechanical properties, because porous materials are usually brittle. As the monomer, we used an aliphatic urethane diacrylate (AUD, Sartomer CN 965), which was added into an emulsion with a high percentage of the internal phase. The emulsion was stirred for one hour in a flask immersed in thermostated water with a stirrer at 250 revolutions per minute. The resulting emulsion was poured into molds and polymerized in an UV oven, then the resulting product was purified in isopropanol and dried. Dried products were analyzed by means of a Scanning Electron Microscope and FTIR. In our experiments we varied the conditions, such as temperature and the proportion of internal phase, solvent, and surfactant. The results showed emulsion formation over a wide temperature range and at various portions of the internal phase, but the products shrunk significantly afer drying, became rigid and inelastic. Further analysis did not show a porous structure of the material in most casses. In order to improve the elasticity and porosity of the material we added different crosslinkers (MBAA and EGDMA) to our monomer and carried out some of our experiments in a nitrogen athmosphere, because the presence of oxygen in the reaction mixture can interfere with the course of polymerization. The tested crosslinkers improved porosity of the material, but the materials were more brittle. The usage of a nitrogen atmosphere resulted only in the formation of non-homogeneous emulsions that did not polymerize well