Amorf silika dolgulu poliüretanüre nanokompozitler

Novel, fumed silica filled thermoplastic polyether based and polydimethylsiloxane based segmented copolymers were synthesized and characterized. Polyether based polyurethaneureas were prepared by a two-step polymerization method from a cycloaliphatic diisocyanate, hydroxyl terminated poly(ethylene oxide) (PEO) and polyt(tetramethylene oxide) (PTMO) with number average molecular weight of 2000 g/mol and 2-methyl-1,5-diaminopentane chain extender. Silicone-urea copolymers were synthesized from aminopropyl terminated polydimethylsiloxane (PDMS) oligomers with number average molecular weights of 32,000 and 2,500 g/mol and from cycloalphatic diisocyanate in one step. Two different types of fumed silica HDK H2K (hydrophobic) and HDK N20 (hydrophilic) were incorporated into the segmented copolymers in amounts of 5-40% by weight. Influence of the silica type (hydrophilic versus hydrophobic), the amount of silica loading and the type of the soft segment on the morphology and tensile properties of the nanocomposites were determined. Major observations of this study were: (i) Incorporation of fumed silica affects the packing and organization in PEO and PTMO soft segments, (ii) incorporation of silica does not affect the glass transition temperature of PDMS, (iii) fumed silica incorporation interfere wih the H-bonding of urea and urethane groups of segmented polyether based urethaeureas. (iv) Hydrogen bonding within the hard domains are disrupted upon fumed silica incorporation in polyether based polyurethaneureas. But, there is no difference in the H-bonding characteristics of the urea groups in the segmented silicone-urea copolymers. No change in the morphology of the corresponding nanocomposites are observed. (v) Incorporation of silica influences the tensile properties of silicone-urea segmented copolymers significantly, whereas the tensile properties of the polyether based systems do not improve upon fumed silica addition.