Search results for "elastomer"
showing 10 items of 134 documents
Structural investigation of hybrid nanocomposites
2002
Ultra small (USANS) and small angle neutron scattering (SANS) techniques were employed to study an elastomer styrene–butadiene, where two kinds of silica fillers have been added in different amounts. Small silica-particle fillers are expected to modify morphological and mechanical properties when dispersed in the copolymer matrix. The USANS and SANS techniques can span a wide range of momentum transfer, investigating morphological properties of the filled elastomer over a number of decades in length scale. Surface and mass fractal behavior has been observed over different length scales.
Silicone-Silver Penile Prosthesis: Description, Operative Approach and Results
1980
A silicone penile prosthesis in which silver wires are embedded to allow for voluntary bending of the penis for urination and resting position and for straightening for intercourse is described. The implantation is done via a hemicircular incision on the dorsum of the penis in the sulcus coronarius. Buck's fascia is identified and opened, and the corpora are dilated up to 30F. After the exact length is determined with a special sizer the prosthesis is slipped into each corpus cavernosum. The advantage of this approach is the optimal insertion of the prosthesis distal to the sulcus coronarius, thereby preventing kinking of the glans during intercourse. Our experiences with the implantation i…
Transrenal Ureteral Occlusion with a Detachable Balloon
1982
Transrenal ureteral occlusion using a detachable balloon was successfully employed to stop urinary flow in seven patients. The balloon was filled with low-viscosity silicone rubber and released in the distal ureter. Percutaneous nephrostomy provided external drainage. Indications were painful dysuria and large urinary fistulas in advanced pelvic malignancy. The method is preferable to ureteral embolization with tissue adhesive.
High-performance thermoplastic elastomers/carbon nanotubes nanocomposites: Mechanical behavior, rheology, and durability
2015
Advanced polystyrene-b-polybutadiene-b-polystyrene (SBS) based nanocomposites containing bare carbon nanotubes (CNTs) and CNTs bearing hydroxyl functional groups (CNTs-OH) have been formulated and fully characterized. In particular, the reinforcement effect of CNTs and CNTs-OH on SBS was deeply investigated through mechanical and dynamical thermo-mechanical analysis and the rheological response of SBS-based nanocomposites was investigated and discussed. The mechanical properties of SBS/CNTs and even more of SBS/CNTs-OH nanocomposites are substantially superior to those of neat SBS, due to the uniformly dispersed nanofillers throughout the polymeric matrix. The presence of -OH groups onto CN…
Permeability measurements in cobalt ferrite and carbonyl iron powders and suspensions
2002
Abstract Magnetic permeability data of cobalt ferrite and carbonyl iron suspensions are discussed. Using an induction method, the relative differential permeability, μr,dif, was measured as a function of the internal magnetic field for different volume fractions of the solid phase. In the case of cobalt ferrite suspensions, the μr,dif−H curve was obtained for a first increasing ramp of magnetic field (data series “1”), a decreasing ramp (data series “2”), and the second increasing one (data series “3”). Series “1” showed a maximum in the μr,dif−H trend that did not appear in series “2” and “3”. Furthermore, the data in series “2” and “3” are always below those in series “1”. The latter beha…
Iris-Like Tunable Aperture Employing Liquid-Crystal Elastomers
2014
A liquid-crystal elastomer (LCE) iris inspired by the human eye is demonstrated. With integrated polyimide-based platinum heaters, the LCE material is thermally actuated. The radial contraction direction, similar to a mammalian iris, is imprinted to the LCE by a custom-designed magnetic field. Actuation of the device is reproducible over multiple cycles and controllable at intermediate contraction states.
Microfluidic Preparation of Liquid Crystalline Elastomer Actuators
2018
This paper focuses on the microfluidic process (and its parameters) to prepare actuating particles from liquid crystalline elastomers. The preparation usually consists in the formation of droplets containing low molar mass liquid crystals at elevated temperatures. Subsequently, these particle precursors are oriented in the flow field of the capillary and solidified by a crosslinking polymerization, which produces the final actuating particles. The optimization of the process is necessary to obtain the actuating particles and the proper variation of the process parameters (temperature and flow rate) and allows variations of size and shape (from oblate to strongly prolate morphologies) as wel…
Induced roughness in thin films of smectic-C* elastomers
2002
The surface topography of a thin homeotropically oriented film of ferroelectric smectic-C* elastomer is studied by atomic force microscopy. We find that when the film is mechanically stretched, its surface becomes increasingly rough, in proportion to the applied strain. The effect depends strongly on the nature of crosslinks forming the elastomer network. The r.m.s. roughness correlations show a consistent trend [h(x) − h(0)]21/2 ~ (x/ξ)0.5. We introduce a theoretical model assuming that random disorder in the smectic tilt angle is induced by deformations via the coupling of mesogens to the elastic network. The model describes the observed power law and gives a prediction for the correlatio…
Microactuators: Control of the Properties of Micrometer Sized Actuators from Liquid Crystalline Elastomers Prepared in a Microfluidic Setup (Adv. Fun…
2010
In this article new results on the preparation of monodisperse particles from a liquid crystalline elastomer in a microfluidic setup are presnted. For this, droplets from a liquid crystalline monomer are prepared in a microfluidic device and polymerized while they are flowing inside a microtube. The particles obtained by this method possess an internal orientation, which gives them actuating properties. When they are heated into the isotropic phase of the liquid crystalline material they show a reversible change in shape whereby they change their length in one direction by almost 100%. It is shown how the variation of experimental parameters during their synthesis impacts the properties of…
Microfluidic synthesis of micrometer-sized photoresponsive actuators based on liquid crystalline elastomers
2016
The fabrication of photoresponsive micrometer-sized liquid crystalline elastomer (LCE) particles has been described in this article for the first time. The preparation of the LCE particles using a microfluidic device by a continuous “on the fly” technique allows their fast processing with an irradiation time of less than 2 seconds. In order to accelerate the polymerization and to make the preparation of samples with thicknesses of several hundred microns possible, we modified a NIR-photoinitiation system by adding a bleaching agent. In addition to the photoinitiator, a side-chain liquid crystalline monomer containing an azo-group and a LC-crosslinker were used in the polymerization mixture.…