Synthesis and properties of polysiloxane elastomers and composites.

摘要

There are four major aspects in this dissertation: the reinforcement of poly(dimethylsiloxane) (PDMS) elastomers, inorganic/organic hybrid materials, thermoelasticity study of different PDMS networks, and structural characterization of the PDMS-zeolite system. All these four aspects concern the PDMS elastomer.; A series of novel fillers, specifically silica-titania, silica-zirconia and silica-aluminia mixed oxides, have been successfully in situ precipitated into an elastomeric network through a sol-gel approach. Compared with silica-filled networks, these novel fillers can offer not only high modulus, but also high extensibility. Filler particle diameters are several hundred angstroms, depending on the crosslink density of networks.; A series of PDMS-modified SiO{dollar}sb2{dollar} and SiO{dollar}sb2{dollar}/TiO{dollar}sb2{dollar} glasses have been successfully prepared using a sol-gel process. The hydrolysis and sol-gel transition reaction of PDMS-modified SiO{dollar}sb2{dollar} glasses have been studied by Nuclear Magnetic Resonance (NMR), Gel Permeation Chromatography (GPC), solvent extraction, and a shear modulus test. It was found that co-condensation between TEOS and PDMS was the dominant reaction under the chosen reaction conditions, and the majority of the PDMS was incorporated into the SiO{dollar}sb2{dollar} network.; End-linking reactions were used to convert chains of PDMS into (i) unfilled networks having either unimodal or bimodal chain-distributions, or (ii) filled networks in which either a separately-prepared zeolite had been blended into the polymer prior to end linking, or silica was precipitated into the networks afterwards. The resulting elastomers were studied in torsion. The values of M{dollar}sb{lcub}rm e{rcub}{dollar}/M were found to be independent of crosslink density, extent of torsional strain, and extent of any elongation imposed during the torsion. The values for the bimodal networks, however, were much smaller than those for the unimodal ones.; PDMS elastomers were filled with two zeolites which were both silicates of sodium and aluminum, but of different cavity size. The reinforcement the particles provided was characterized by stress-strain measurements in elongation at room temperature. The results indicated that the ultimate properties of the networks were increased by both types of zeolites, but that the increase was larger in the case of the zeolite with the larger cavity size. (Abstract shortened by UMI.)