Search results for "poly(tetrafluoroethylene)"
showing 10 items of 32 documents
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…
Influence of photo-initiators in the preparation of methacrylate monoliths into poly(ethylene-co-tetrafluoroethylene) tubing for microbore HPLC.
2020
[EN] In this study, poly(butyl methacrylate-co-ethyleneglycol dimethacrylate) polymeric monoliths were in situ developed within 0.75 mm i.d. poly(ethylene-co-tetrafluoroethylene) (ETFE) tubing by UV polymerization via three different free-radical initiators fscce-azobisisobutyronitrile (AIBN), 2,2-dimethoxy-2-phenylacetophenone (DMPA) and 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (MTMPP). The influence of the nature of each photo-initiator and irradiation time on the morphological features of the polymer was investigated by scanning electron microscopy, and the chromatographic properties of the resulting microbore columns were evaluated using alkyl benzenes as test substances. The …
Wet-chemical approach for the cell-adhesive modification of polytetrafluoroethylene
2011
Polytetrafluoroethylene (PTFE), a frequently utilized polymer for the fabrication of synthetic vascular grafts, was surface-modified by means of a wet-chemical process. The inherently non-cell-adhesive polymer does not support cellular attachment, a prerequisite for the endothelialization of luminal surface grafts in small diameter applications. To impart the material with cell-adhesive properties a treatment with sodium-naphthalene provided a basis for the subsequent immobilization of the adhesion promoting RGD-peptide using a hydroxy- and amine-reactive crosslinker. Successful conjugation was shown with cell culture experiments which demonstrated excellent endothelial cell growth on the m…
Stimuli-Responsive Y-Shaped Polymer Brushes Based on Junction-Point-Reactive Block Copolymers
2012
Reversibly responsive, thin or ultrathin polymer fi lms, often referred to as “smart surfaces”, can alter their properties upon application of external stimuli. [ 1 , 2 ] One particular application fi eld represents the engineering of nanostructured fi lms mimicking cell membranes. [ 3 , 4 ] Such materials offer application potential for sensors, textiles, construction materials, and smart coatings due to a rapid change in surface energy and morphology. [ 5–7 ] The surface response can be triggered by various external stimuli such as light, temperature, electrical potential, mechanical force, magnetic fi eld, pH change, or selective solvent treatment. [ 1 , 8–12 ] A variety of different thi…