| Sustainability regarding the most produced plastic, polyethylene, was the main motivation factor behind research of this thesis. The aim was to synthesize hybrids of polyethylene and starch in an aqueous mini emulsion polymerization process using single-site catalysts. Two types of water soluble starches were applied: potato and hydroxyethyl starch. A trifluoromethane bearing nickel enolate catalyst and a 5-halo 3-methoxy salicyl aldiminate nickel pyridyl catalyst (with Cl and Br as halogen atoms) were used as polymerization catalysts, the latter two known to results in higher molecular weight polymer. The first catalyst turned to be sufficiently active with increased loads of starch and resulted in hybrids containing between 7.5 and 92.3 % starch. The salicylaldiminate catalysts only led to traces of polyethylene since the applied ethylene pressure of ca. 7.5 bar in the glass reactor was not sufficiently high to polymerize in aqueous solution. The hybrids were characterized using IR spectroscopy, TGA, density measurements, DSC, SEM and TEM. For the determination of the starch content the aqueous latex samples had to be washed with acetone to remove the surfactant (sodium dodecyl sulfate,) and co-surfactant (hexadecane). The SEM and TEM showed that the starch was uniformly distributed in the hybrids. Biodegradability tests were carried out with three different types of fungi, Aspergillus, Trichoderma, and Myrothecium for 21 days. Aspergillus turned out to be the most active in the metabolization of the starches with hydroxymethyl starch being degraded more rapidly than potato starch. The biodegraded samples were also characterized by IR, TGA, and DSC and SEM, verifying that the starch and soap were metabolized by the fungi whereas the polyethylene was not. The crystallinity of the polyethylene was slightly increased as a result of the biodegradation. |
