Search results for "Tetrafluoroethylene"
showing 10 items of 38 documents
Preparation of organic monolithic columns in polytetrafluoroethylene tubes for reversed-phase liquid chromatography
2017
[EN] In this work, a method for the preparation and anchoring of polymeric monoliths in a polytetrafluoroethylene (PTFE) tubing as a column housing for microbore HPLC is described. In order to assure a covalent attachment of the monolith to the inner wall of the PTFE tube, a two-step procedure was developed. Two surface etching reagents, a commercial sodium naphthalene solution (Fluoroetch®), or mixtures of H2O2 and H2SO4, were tried and compared. Then, the obtained hydroxyl groups on the PTFE surface were modified by methacryloylation. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy and scanning electron microscopy (SEM) confirmed the successful modification…
Photografted fluoropolymers as novel chromatographic supports for polymeric monolithic stationary phases
2018
[EN] In this study, porous polymer monoliths were in situ synthesized in fluoropolymers tubing to prepare microbore HPLC columns. To ensure the formation of robust homogeneous polymer monoliths in these housing supports, the inner surface of fluoropolymer tubing was modified in a two-step photografting process. Raman spectroscopy and scanning electron microscopy (SEM) confirmed the successful modification of the inner poly(ethylene-co-tetrafluoroethylene) (ETFE) wall and the subsequent attachment of a monolith onto the wall. Poly(glycidyl methacrylate-co-divinylbenzene), poly(butyl methacrylate-co-ethyleneglycol dimethacrylate) and poly(styrene-co-divinylbenzene) monoliths were in situ synt…
A Novel Technique Using Polytetrafluoroethylene Tape to Solve Screw Loosening Complication in Implant-Supported Single Crowns
2020
This study aimed to analyze a novel technique to make screws with greater untightening resistance and to solve screw loosening in implant-supported single crowns. Thirty grade IV titanium straight abutments were screwed onto 30 external hex implants using grade IV titanium screws (30 Ncm). They were exposed to cyclic loading (300,000 cycles, 200 N). Samples were divided into 4 groups (15 samples per group): new screws (SCREW group) (control), reused screws (rSCREW group), new screws wrapped with polytetrafluoroethylene (PTFE) tape (PTFE group), and reused screws wrapped with PTFE tape (rPTFE group). Reverse torque values (RTVs) were recorded with a digitally calibrated implant motor. Mean R…
Resource or waste? A perspective of plastics degradation in soil with a focus on end-of-life options.
2018
‘Capable-of-being-shaped’ synthetic compounds are prevailing today over horn, bone, leather, wood, stone, metal, glass, or ceramic in products that were previously left to natural materials. Plastic is, in fact, economical, simple, adaptable, and waterproof. Also, it is durable and resilient to natural degradation (although microbial species capable of degrading plastics do exist). In becoming a waste, plastic accumulation adversely affects ecosystems. The majority of plastic debris pollutes waters, accumulating in oceans. And, the behaviour and the quantity of plastic, which has become waste, are rather well documented in the water, in fact. This review collects existing information on pla…
Some Features of Polymeric Membranes for Water Purification via Membrane Distillation
2011
Polymeric membranes are currently adopted in water purification processes, such as reverse osmosis (RO) and membrane distillation (MD). This latter technique is very promising for separation effectiveness and energy savings. A valuable and effective MD unit must be equipped with polymeric membranes that exhibit specific properties, for example, hydrophobicity, a narrow pore size range, a high water penetration pressure, and a large vapor permeability. In this work, we present and examine the main features of membranes for MD processes, with the aim of experimentally evaluating the related performances. Scanning electron microscopy analysis was carried out for a first estimate of the pore si…
Implantation of Gore-Tex chordae on aortic valve leaflet to treat prolapse using "the chordae technique": surgical aspects and clinical results.
2008
Background Repair of prolapsed aortic valve leaflets has been considered a challenging technique for cardiac surgeons. In this paper we describe our surgical approach, "the chordae technique." It consists of the correction of aortic cusp prolapse by shortening the free margin length and of an adjustment of the leaflets coaptation height by anchoring the prolapsing cusp to the aortic wall at the sinotubular junction level. Methods Between February 2003 and December 2006, 26 patients with one or more prolapsed aortic leaflets underwent surgical repair using the new approach. The mean age of patients was 55 ± 10 years. There were 10 (38.5%) patients with grade II aortic valve regurgitation, 4 …
External reinforcement of varicose veins with PTFE prosthesis in infrainguinal bypass surgery -- clinical results.
2003
OBJECTIVE Segmental varicose degeneration of the autogenous greater saphenous vein may limit its use in infrainguinal bypass surgery. Wrapping a PTFE prosthesis around dilated veins has emerged as an option to create externally reinforced vein bypasses. Results regarding graft patency and limb salvage were analyzed. METHODS Between September 1995 and January 2001, 35 infrainguinal bypass operations in 33 patients were performed with greater saphenous veins exhibiting segmental varicose dilatation. Grafts were followed by duplex scan and retrospective analysis of graft patency and limb salvage was performed. RESULTS One bypass prompted successful revision for early occlusion. Four bypasses r…
Endoluminal Stent-Graft Relining of Visceral Artery Bypass Grafts to Treat Perigraft Seroma
2013
PURPOSE: To describe the endovascular treatment of intra-abdominal perigraft seromas associated with small-caliber expanded polytetrafluoroethylene (ePTFE) grafts. CASE REPORTS: Two patients who underwent hybrid repair of thoracoabdominal aortic aneurysms in which renovisceral bypass grafts were implanted presented with large, symptomatic perigraft seromas. The 5- to 8-mm-diameter ePTFE bypass grafts believed to be involved in the seromas were successfully relined with self-expanding Viabahn stent-grafts in percutaneous procedures. The patients' symptoms were relieved, and imaging follow-up (18 and 10 months, respectively) has shown near complete resorption of the seromas. CONCLUSION: It is…
Non-cross-linked porcine-based collagen I-III membranes do not require high vascularization rates for their integration within the implantation bed: …
2012
There are conflicting reports concerning the tissue reaction of small animals to porcine-based, non-cross-linked collagen I-III membranes/matrices for use in guided tissue/bone regeneration. The fast degradation of these membranes/matrices combined with transmembrane vascularization within 4 weeks has been observed in rats compared with the slow vascularization and continuous integration observed in mice. The aim of the present study was to analyze the tissue reaction to a porcine-based non-cross-linked collagen I-III membrane in mice. Using a subcutaneous implantation model, the membrane was implanted subcutaneously in mice for up to 60 days. The extent of scaffold vascularization, tissue …
Reactive Surface Coatings Based on Polysilsesquioxanes: Controlled Functionalization for Specific Protein Immobilization
2009
The key designing in reliable biosensors is the preparation of thin films in which biomolecular functions may be immobilized and addressed in a controlled and reproducible manner. This requires the controlled preparation of specific binding sites on planar surfaces. Poly(methylsilsesquioxane)-poly(pentafluorophenyl acrylates) (PMSSQ-PFPA) are promising materials to produce stable and adherent thin reactive coatings on various substrates. Those reactive surface coatings could be applied onto various materials, for example, gold, polycarbonate (PC), poly(tetrafluoroethylene) (PTFE), and glass. By dipping those substrates in a solution of a desired amine, specific binding sites for protein ads…