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[en] Highlights: Femtosecond laser was used to irradiate PTFE to form composite microstructures. The treated PTFE surface exhibits superhydrophobic and superoleophobic properties. The mechanism of wettability is explained with the CassieBaxter model. We report a simple method to fabricate superamphiphobic polytetrafluoroethylene (PTFE) surfaces by femtosecond laser direct irradiation. After femtosecond laser direct writing, a dual-scale composite structure combined a groove-like microstructure with a lamellar submicron structure forms on the PTFE surface, enhancing its hydrophobic properties with a contact angle increasing from 109° to 156.88°, as well as exhibiting transition from intrinsic oleophilicity to superoleophobicity. Meanwhile, the wettability of the surface can be tuned by changing the roughness and the interval between two adjacent micro-grooves. Furthermore, we also explain the relationship between the interval width and the contact angle using the CassieBaxter model.
[en] Highlights: • The effect of W content on the reaction energy of W–PTFE–Al composites in both oxygen and argon were investigated. • The effect of W content on the quasi-static and dynamic compression properties of W–PTFE–Al composites was studied. • The effect of W mass ratio on the impact insensitivity of W–PTFE–Al composites was studied. Reaction energy, mechanical behavior, and impact initiation of three kinds of tungsten (W)–polytetrafluoroethylene (PTFE)–aluminum (Al) composites are investigated. The reaction energy results show that, the reaction energy of W–PTFE–Al composites in both oxygen and argon decreases with the mass ratio of W increased from 50% to 80%. Quasi-static compression results show that, the increased mass ratio of W has no obvious influence on the strength of W–PTFE–Al composites. However, the critical failure strain presents obviously decreasing tendency with the increased mass ratio of W. Dynamic compression results show that, the strength enhances with the increased W in W–PTFE–Al. The critical failure strain shows no obvious difference when the W content of W–PTFE–Al increases. Under impact condition, the deflagration time of all the three kinds of W–PTFE–Al composites lasts for about 500 μs. The insensitivity to impact loading shows an increasing tendency with the increased W mass ratio. During impact compressive deformation, the PTFE matrix is elongated in nano-fibers, thus significantly increases the reaction activity of W–PTFE–Al composites. The nano-fiber structure is necessary for the reaction of W–PTFE–Al composites. The formation of PTFE nano-fibers must undergo severe plastic deformation, which is responsible for the excellent insensitivity of W–PTFE–Al composites.
[en] Dynamic loading experiments were performed on inert Teflon (Polytetrafluoroethylene) samples, initially heated to the temperature of 200 C, to test its behavior under these conditions for its use in other heated experiments. Tests were performed in the 100 mm diameter bore propellant driven gas gun with piezo-resistive manganin pressure gauges imbedded into the samples to measure loading pressures. Experimental data provided new information on the shock velocity - particle velocity relationship for the heated material and showed no adverse effect of temperature on the insulating properties of the material
[en] This work quantifies the adsorptive uptake of radium-226 from solution by the walls of the solution container. Three different container materials were examined, each with significantly different critical surface tension. Teflon was shown to be the material with the least radium-226 adsorption capacity in the examined pH range of 2 to 10. The radium adsorption by Teflon flasks is consistent and predictable. The respective adsorption isotherm is presented. An optimum washing procedure for the Teflon flasks was also defined
[en] This study evaluates AngioJet thrombectomy of occluded autogenous dialysis fistulae and polytetrafluoroethylene (PTFE) grafts in a UK hemodialysis population. Comparison is made with published data of alternative percutaneous thrombectomy methods. All patients with occluded dialysis fistulae who sought care at the Royal Liverpool University Hospital between October 2006 and June 2008 were included in the study. All patients were treated with the AngioJet Rheolytic Thrombectomy Device (Possis, Minneapolis, MN). Demographics, time of occlusion, adjunctive therapies, complications, and follow-up data have been prospectively recorded. A total of 64 thrombectomy procedures were performed in 48 patients. Forty-four autogenous fistulas were treated in 34 patients (19 brachiocephalic, 8 radiocephalic, and 7 transposed brachiobasilic). Twenty PTFE grafts were treated in 14 patients (9 brachioaxillary, 3 brachiocephalic loop grafts, 1 brachiobasilic, and 1 femoro-femoral). The average length of occlusion was 24 cm. Average time to intervention was 4 days. Immediate primary patency was 91%. Primary patency at 1, 3, and 6 months, respectively, was 71%, 60%, and 37%. Secondary patency at 3, 6, and 12 months was 87%, 77%, and 62%, respectively. Angioplasty was carried out in all procedures. Patients required stent insertion in 34 of the 64 thrombectomies to treat angioplasty-resistant stenoses. Complications included a puncture-site hematoma, and three angioplasty-related vein ruptures in one patient, all treated with covered stent grafts. Two cases of distal brachial arterial embolization were successfully treated by thrombosuction. AngioJet thrombectomy in dialysis access occlusion is safe and effective, comparing favorably with other methods.
[en] The production of aliphatic perfluoro compounds by means of radiation-chemical degradation reaction of PTFE using an electron beam represents a new alternative of the synthesis of special active components, such as fluorocarbon surfactants, fluorine containing textile finishing agents, special dielectrics and others. A principle of process and an apparatus conception pertaining to it of a continuous degradation of PTFE to perfluoroalkenes and -alkanes in the favourable chain lengths ranges from six to fourteen carbon atoms, according to application, is described. An essential component of this conception is the use of a target which consists of a tempered thin layer which is led, in correspondence with dimension and intensity of the radiation field, in an inertly processed reactor. An embodiment of the reactor is presented in detail. (author)