Five sorts of fluorosilicone oligomers having different fluorooxaalkyl groups (RF) and siloxane chain lengths were synthesized by the reaction of vinyl group-containing poly (dimethyl siloxane) s (VPSs) with bis (fluorooxaalkanoyl) peroxides. Unmodified VPSs were not able to dissipate bubbles caused by sodium dodecyl sulfate in aqueous solutions, while modified VPSs dissipated them did quite well. The foam-dissipation effect was almost independent of RF chain and siloxane chain lengths in the fluorosilicone oligomers, but fairly dependent of their concentrations. From a dynamic surface tension measurements, it was found that the foam-dissipation effect by the fluorosilicone oligomers is closely related to their adsorption rates to an air/water interface.
The temperature dependences of dynamic storage and loss moduli (E' and E “) were measured for magnetic tapes prepared using iron oxide magnetic powder (OP) and metal magnetic powder (MP). On the basis of time-temperature superposition principle, we obtained the master curves of E' and E” of the magnetic tapes in order to examine the effects of cross-linking and curing on viscoelastic properties. These curves indicated that the E' and E “of OP tape were larger than those of MP tape, and the maximum of E” for OP tape shifted greater toward higher angular frequency than that of MP tape. From the temperature dependence of shift factor aT the apparent activation energies ΔHa relating to the relaxation of added vinyl chloride type binder for OP and MP tapes were estimated to be about 60 and 70 kcal/mol, respectively. From the master curves of E', relaxation spectra He (τ) were calculated. It was shown that H (τ), of OP tape was larger than that of MP tape in the broad range of the time scale, and the (τ) peak was shifted to greater time region by the addition of cross-linking agent. As a result, it was found that there was a significant difference of relaxation system between OP and MP tapes, which strongly reflected the characteristics of OP and MP.