ABSTRACT:The hydrolysis rate of alkoxy silane (dimethyldiethoxy silane, DMDES, etc.) is a linear relationship vs. the reaction time under the moisture flux control. The hydrolysis process results in formation of the linear polysiloxane products by a subsequent condensation reaction. An amidized alkoxy silane (3-(2-aminoethyl)aminopropylmethyldimethoxy silane, KLM-602 or ␥-aminopropyl-triethoxy silane, ␥-APS) serves as an internal standard of DMDES hydrolysis kinetics measurements. The hydrolysis kinetics of DMDES with the amidized alkoxy silane and the subsequent linear polysiloxanes conversion have been evaluated and characterized by 29 Si-and 13 C-NMR NMR spectroscopic measurements.

No abstract

Induced surface reconstruction of silicone rubber by blending polydimethylsiloxane (PDMS) reactants with bifunctional PDMS-hydroxyl terminated polybutadiene (PDMS-b-HTPB) copolymers and curing with appropriate mold material was attempted to improve the adhesion of chemically inert silicone rubber to polyurethane (PU). Surface characterization using Fourier transform infrared-attenuated total reflectance indicated that the surface of the silicone rubber possessed a controlled amount of HTPB. The surface was enriched with HTPB by using mold materials having high critical surface tension, such as aluminum. A dynamic surface rearrangement occurred during a 1-h heating cycle at 70°C, changing from an HTPB-enriched surface to a PDMS-enriched surface. The peel strength between the silicone rubber and PU was found to increase with decreased propanol residue and with an increase in critical surface tension of the molding materials. The increased content of surface HTPB was suggested to account for the improved adhesion of silicone rubber to PU.

SynopsisPolyelectrolyte submicron microcapsules were prepared by interfacial crosslinking of an aqueous salt solution of poly(ethy1eneimine) and a toluene solution of brominated poly-(2,6dimethylphenylene oxide). The two solutions were brought together and mixed by sonication. As a result, a stable emulsion was obtained, which was subsequently cast into a membrane in which the microcapsules were embedded. The salt solution contained in the microcapsules could be released under controlled conditions. The rates of release were measured. They could be controlled by applying osmotic pressures, by additional quaternization of the membrane, or by modification of the structure of the capsule wall by introduction of a surfactant.

No abstract