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Silicone Polymer (silicone + polymer)
Selected AbstractsInfluence of Particle Morphology and Flow Conditions on the Dispersion Behavior of Fumed Silica in Silicone PolymersPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 3 2004John Boyle Abstract The dispersion behavior of agglomerates of several grades of fumed silica in poly(dimethyl siloxane) liquids has been studied as a function of particle morphology and applied flow conditions. The effects of primary particle size and aggregate density and structure on cohesivity were probed through tensile and shear strength tests on particle compacts. These cohesivity tests indicated that the shear strength of particle compacts was two orders of magnitude higher than the tensile strength at the same overall packing density. Experiments carried out in both steady and time-varying simple-shear flows indicate that dispersion occurs through tensile failure. In the steady-shear experiments,enhanced dispersion was obtained at higher levels of applied stress and, at comparable levels of applied stress, dispersion was found to proceed faster at higher shear rates. Experiments conducted in time-varying flows further corroborated the results obtained in tensile cohesivity tests. Experiments in which the mean and maximum stresses in the time-varying flows were matched to the stresses produced in steady shear flows highlight the influence of flow dynamics on dispersion behavior. [source] Shade darkening effect of polyorganosiloxane modified with amino and hydroxy groups on dyed polyester microfiber fabricJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2007Kongliang Xie Abstract The novel polyorganosiloxane material S-101 modified with amino and hydroxy groups is synthesized. Shade darkening effect of modified polyorganosiloxane on dyed polyester microfiber fabric is investigated by reflectance spectrum, color yield (K/S), and the color differences (,E). The colorimetric data of CIELAB is discussed. The results show that the novel material of silicone polymer modified with amino and hydroxy groups has excellent shade darkening effect on dyed polyester microfiber fabric. The rates of the color yield increase (I%) of all dyed fabric with four dyes (Disperse Yellow S-4RL, Red GS, Blue 2BLN, and Black SF-R) exceed 10%. The shapes of the reflectance spectra curves of the dyed fabrics before and after treated with S-101 are not noticeable change. The dyed fabrics with the polymer have not significant effect on the wash fastness and wet rubbing fastness. The low reflectance thin film on dyed fabrics is formed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] UV Absorption and Photoisomerixation of p -Methoxycinnamate Grafted Silicone,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2004Supason Pattanaargson ABSTRACT p -Methoxycinnamate moieties, UV-B-absorptive chromophores of the widely used UV-B filter, 2-ethylhexyl p -methoxycinnamate (OMC), were grafted onto the 7 mol% amino functionalized silicone polymer through amide linkages. Comparing with OMC, the resulting poly [3(p -methoxycinnamido)(propyl)(methyl)-dimethyl] siloxane copolymer (CAS) showed less E to Z isomerization when exposed to UV-B light. The absorption profiles of the product showed the maximum absorption wavelength to be similar to that of OMC but with less sensitivity to the type of solvent. Poly (methylhydrosiloxane) grafted with 10 mol%p -methoxycinnamoyl moieties was prepared through hydrosilylations of 2-propenyl- p -methoxycinnamate, in which the resulting copolymer showed similar results to those of CAS. [source] A model to quantify encrustation on ureteric stents, urethral catheters and polymers intended for urological useBJU INTERNATIONAL, Issue 4 2000S.K.S. Choong Objective To validate an encrustation model and to quantify encrustation on currently used urological devices and polymers intended for urological use. Materials and methods An encrustation model was validated: (i) to measure the amount of calcium leaching from the glass model and from the polymer used; (ii) to determine whether the use of a single-source or pooled urine produced similar results; (iii) to determine in vitro encrustation; and (iv) to compare the results of in vivo implantation of the same materials into the bladders of rodents with the in vitro results. A test polymer (a ureteric stent, a urethral catheter or a biomaterial) and a control silicone polymer were housed separately but received human urine from the same reservoir and under the same conditions (pH 6.0 and 37 °C) for 5 days. The amount of calcium encrustation on each polymer was measured using atomic absorption spectroscopy. Each experiment was repeated at least four times and the results expressed as an encrustation index, defined as the ratio of encrustation of the test and reference polymers. Results The amount of calcium leaching from the glass model and polymers tested was insignificant. The use of a single-source or pooled urine gave the same results in the encrustation model. The in vitro results correlated with in vivo implantation of disks into the bladders of rats. Among the commonly used ureteric stents tested, the Cook C-Flex ureteric stents encrusted least. Hydrogel-coated ureteric stents encrusted more than uncoated stents. The Bard polytetrafluoroethylene short-term urethral catheter encrusted more than the Bard hydrogel-coated long-term catheter. A plasma-activated surface modification of a synthetic biomaterial with hyaluronic acid encrusted less than silicone, a long-term biomaterial widely regarded as the ,gold standard'. Conclusion This validated encrustation model is the first to quantify encrustation on currently available ureteric stents and urethral catheters. A novel coating for a biomaterial was identified using the encrustation model, and which encrusted less than silicone. [source] | ||||||||||