Since the first Polyurethanes book was published in , and reprinted with updates in , the world of polyurethanes has changed dramatically. This edition. Get this from a library! The polyurethanes book. [David Randall, Ph. D.; Steve Lee ;]. Introduction to polyurethanes -- The global polyurethanes market -- The life-cycle of polyurethanes -- Product stewardship -- Isocyanates -- Polyols -- Outline of.
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The polyurethanes book by, , Distributed by J. Wiley edition, in English. The way to obtain this book The Polyurethanes Book From Wiley is very easy. You may not go for some places and spend the moment to just locate guide The. Focusing on a range of components used to produce polyurethanes, this book presents an analysis of environmental issues and views on the applications for.
These PUs were prepared by conventional two-step solution polymerization. Using a canine ex vivo shunt experiment, PU-coated polyethylene tubings were tested for short term platelet and fibrinogen deposition.
The relatively good results observed with PDMS-based PU were imparted to the hydrophobic nature of the polymer surface. Here again, the authors concluded that the initial rate of platelet adhesion increased with an increase in hydrophilicity of the various polyol used in the synthesis of the PUs, thus, confirming that the blood compatibility of polyurethanes may depend on a combination of factors including microphase separation, surface heterogenicity, and surface hydrophilicity. In a questionable in vitro blood chamber experiment, they reported data on platelet behaviour for PTMO polyurethanes while omitting those of the PEO polyurethanes.
They found no significant difference between PTMO-based polyurethanes of molecular weight ranging between and Mw and provided no substantial conclusion.
These polyurethane materials have been shown to display varying degrees of antithrombotic activity. Thrombin time experiments showed no significant heparin-like properties to sulfonated PUs with lysine or aspartic acid although an increase in thrombin time was shown for those sulfonated PU with increased sulfonate content.
Ishihara et al have incorporated various MCP polymers copolymerized with cyclohexyl methacrylate or 2-ethylhexyl methacrylate EHMA into Tecoflex60 using the same solvent.
Following incubation in whole blood or platelet-rich plasma PRP , platelet adhesion was assessed by scanning electron microscopy SEM. The authors suggested that a reduction of plasma protein adsorption on PU-MCP membranes might explain their results.
Li et al introduced new PUs based on cholesterol and phosphatidylcholine analogous moieties. The hydrophobic nature of the hydrocarbon-based polydiols was the only argument used by the authors to explain their results.
In a second study, Li et al were interested in blending phospholipid diols with long chain alkyl groups C16 to C20 because of their claimed blood compatibility, excellent mechanical properties, and nonether soft segment composition.
Again, the apparent number of platelets and their morphological changes after incubation in PRP for 60 min were assessed by SEM. The authors suggested better blood compatibility properties for HPIP-based phospholipid PUs with saturated long chain alkyl groups C16, C18, and C20 and claimed their potential for wide biomedical applications. A relative index platelet adhesion RIPA was used as a hemocompatible parameter.
Results showed lower platelet adhesion with IPNs containing 25 wt. Surface Modifications of Polyurethanes In the last decade, a number of surface modifications have been proposed to improve the antithrombotic properties of polyurethanes, bearing in mind that the primary factor in determining the blood compatibility of any materials is the material surface chemistry.
The methods include coating or impregnation processes, photo-chemical immobilization reactions and various grafting techniques using surface derivatization or oxidation, ionization, or polymerization. Grafting Techniques In a chronic ex vivo arterio-venous shunt experiment, McCoy et al studied six different materials simultaneously in terms of radiolabelled platelet deposition and SEM viewing.
The results demonstrated that the alkyl grafted C18 PEU was the most thrombogenic of all materials in terms of platelet deposition. Their findings were in disagreement with those of Grasel et al 39 and Li and Nakaya 36 although the platelet adhesion test differed slightly. Again, sulfonated PEU materials appear to exhibit nonthrombogenic behaviour as previously reported.
In a series of blood incubation tests, AMPS-PU was shown to reduce the generation of fibrinopeptide A, b-thromboglobulin and C3a as well as decreasing the adherence of platelets and neutrophils in vitro.
However, conflicting results were observed in vivo as a greater amount of adherent thrombus formation and increased attraction of macrophages to the material were observed with AMPS-PU. Although confering heparin-like characteristics to AMPS derivatization grafting on biomaterial surfaces, the authors expressed caution in extrapolating in vitro results to the in vivo situation. They suggested that the better blood compatibility of the DMAA-grafted PU may be due to weaker interaction of the grafted material with the blood components as frequently reported for other materials.
As previously reported by Ishihara et al, 33 phosphorylcholine-adsorbed PEU surfaces exhibited prolonged clotting times and reduced platelet adhesion with increased concentrations of phosphorylcholine at the surface compared to unmodified PEU surfaces. Using a flow-controlled chamber method, they showed anti-factor Xa activity on the grafted surface as well as reduced platelet adhesion compared to unmodified PU surface.
Their study confirms previously reported studies showing the benefits of PEO and of SO3 in improving the blood compatibility of PU surfaces. Reviewing all the research with heparin would be fastidious and only recent innovative approaches will be discussed here. Through the years, surfaces bearing ionically bound heparin have encountered major difficulties, namely, temporary anticoagulant activity and elution from the surface which may jeopardize long-term applications.
Heparinizable PUs may be obtain by different methods. First, a chain extension reaction may be performed with chain extenders containing amine on hydrolizable ester groups in their backbone or side chain.
Heparin may then be covalently bound by coupling reactions between the free hydroxyl or amine groups on heparin and the free isocyanate group on an hydrophilic spacer such as PEO.
Among the strategies that increase the immobilizing site, graft polymerization may be an effective method using functional group grafting by oxygen plasma glow discharge followed by graft polymerization. Heparin-immobilized PUs have been prepared by coupling reactions of NH2 and COOH functional groups with heparin, 50 and more recently with acrylic acid, 51 and acryloylbenzothiazole AB.
Peripheral blood mononuclear cells were also shown to adhere less and secrete lower tumor necrosis factor after contact with heparinized PUs. Authors acknowledged that their results with AB grafted on PU surfaces were not promising with regard to blood contact applications. Biocompatibility of Polyurethanes In vitro and in vivo biocompatibility studies investigating various polyurethanes for a wide range of applications have focused on the cellular, enzymatic, and tissue responses to the material.
The Polyurethanes Book
These interactions between cells and synthetic materials have been the subject of extensive research because of the implication of biomaterials on substituting and maintaining organs or tissue functions. In vitro testing procedures are a fundamental part of any material evaluation. They include cytotoxicity tests which investigate the effect of extractables from the biomaterial on cell morphology, viability or function. Direct contact assays using fibroblasts or endothelial cells are also frequently used for the determination of the cellular response toward biomaterials.
Among the cell type used for these tests, the fibroblast and endothelial cells are the most commonly used for cytotoxicity tests. Other types of cells may be used and include the neutrophil, lymphocyte, monocyte, epithelial cell as well as specific cells which will be in contact with the biomaterial upon implantation for different applications such as the skin, the blood, the tympanum, and the cornea. In vivo studies have also been developed to assess the cellular or tissue responses of polyurethanes either subcutaneously, intramuscularly, or intraperitoneally.
Again, other implantation sites such as those receiving the implant may be recommended and include the cardiovascular system artificial heart, 63 vascular grafts, 64—68 stents, 69 sink hole valves, 70 and catheters 41 , the middle ear tympanic membrane 71 and the eye intraocular lenses 72 , the esophagus, 73 ureteric, 74 and biliary tract 75 stents and endoprostheses.
In Vitro Biocompatibility Testing of Polyurethanes The biocompatibility of polyurethanes has been assessed in vitro using various cell culture techniques. For the last two decades, the group of Anderson at Case Western Reserve University has been involved in elucidating the cellular interactions with biomaterials, especially those induced by a segmented polyether-urethane, Biomer.
Their studies also included various polymers for comparison purposes. Results demonstrated that Biomer induced low monocyte reactivity in terms of interleukin-1 IL-1 secretion which was found to be similar to PDMS.
The Polyurethanes Book
These findings may have a serious impact on the biofunctionality of prostheses or implants made of Biomer upon implantation. In other words, a biocompatible polymer does not necessarily mean that the healing of the device will be optimal and satisfactory.
When reviewing the literature on the in vitro biocompatibility testing of polyurethanes, we found only a limited number of papers describing the biocompatibility of well-characterized polyurethanes. Most of these studies report good biocompatibility of polyurethanes in general. When conducting biocompatibility studies on PUs, one must include appropriate control materials or materials with clinical relevance for a specific application.
In a vascular application, various polyurethane vascular grafts were compared for cytotoxicity and endothelial cell behaviour using organotypic culture assays. The authors recognized that the surface characteristics of a biomaterial may have a potential effect on cell behaviour. In another study, Ertel et al reported on the intrinsic toxicity of various materials including a polyether-urethane. Investigating a number of vascular grafts having different chemistry and surfaces, we have recently been able to identify to some extent which type of chemistry or structure may generate optimal cell growth using an organotypic culture technique.
As previously reported, textured porous surfaces as opposed to smooth surfaces have been shown to stimulate both cell growth and metabolism. Moreover, cell adhesion is said to be regulated by substrate wettability, surface charge, and roughness. Lee et al also suggested that there are two crucial factors which should be considered when determining cell attachment and proliferation properties at the surface of a polyurethane.
These elastomers possess attractive chemical and mechanical properties and exhibit relatively good biocompatible characteristics.
Polyurethane Polymers: Blends and Interpenetrating Polymer Networks
However, extrapolating in vitro results to the in vivo situation should be done with proper caution. In Vivo Biocompatibility Studies of Polyurethanes In the last three decades, a substantial amount of in vivo studies has been published on various polyurethanes used in the construction of the artificial heart, heart valves, pacemakers, vascular grafts, stents, endoprostheses and catheters.
Although many studies confirmed the excellent mechanical properties and favourable biofunctionality of these devices, only a few reports have been concerned with the chemical stability oxidation and the degradation mineralization, environmental stress-cracking of segmented PUs.
Consequently, a number of modifications have been attempted to reduce mineralization and oxidation, stabilize the hydrophobic-hydrophilic domains, increase the resistance to degradation and enhance the mechanical properties through innovative polymer synthesis. Recently published, more significant papers which compare PUs of various chemical composition or modification will be reviewed to assess those exhibiting good compatibility after implantation.
As reviewed by Coury et al, 93 it was only during the s that calcification, environmental stress-cracking, and oxidation phenomena in vivo were brought to the attention of scientists involved in the synthesis of PU elastomers and devices.
The first interest was in the segmented polyether-urethane Biomer frequently used in several biomedical applications. Biomer was found to be relatively stable with implantation time 94 , 95 although some microscopic defects at the surface were reported.
They suggested that implant surface properties influence the inflammatory response shortly after implantation and modulated further cell activation and proliferation.
On the other hand, they recognized that their model was not able to generate any correlations between the materials studied and cell fusion kinetics. When compared to PVC, Tecoflex-based membranes were shown to elicit a greater chronic inflammatory response. The authors suggested that the plasticizer released during the course of implantation might have triggered the inflammatory response. In their experiment, the net charge of PEU was modified by introducing different concentrations of sulphonate ionic groups in the PEU backbone giving a range of negative charge.
However, it has been recognized that the use of these compounds may compromise the biological response if too concentrated or if their oxidation degradation products have undesirable toxicity. The use of a natural antioxidant vitamin E was recently investigated in a PEUU elastomer for surface degradation characteristics, chemical stability and inflammatory response in a cage implant exudate study. It was shown that vitamin E prevented surface cracking and chemical degradation up to five weeks in vivo.
Changes to the soft segment chemistry may include substitution of polyether segments with polybutadiene, polydimethylsiloxane, polycarbonate, and other aliphatic hydrocarbon segments.
Incorporation of PDMS in PUs was shown to exhibit good blood compatibility, low toxicity, good thermal and oxidative stability, low modulus, and anti-adhesive properties see Chapter 6. Studies have also confirmed that polycarbonate soft segment was more stable than polyether soft segment.
With studies lacking findings on the biostability and biological response of these modified PUs, Mathur et al recently reported the effects of chemical composition variation of the soft segment on the chemical stability, the rate of degradation and the inflammatory response to modified PUs.
These findings were attributed to the hydrophobic nature of PDMS end groups. Polycarbonates showed slightly less macrophage attack as compared to PEUs. Again, the authors suggested that PDMS might provide a shield against oxygen radicals secreted by inflammatory cells and consequently reduced the rate of biodegradation. In addition, it was found that only a minor amount of biodegradation was seen on polycarbonate-urethanes as compared to unmodified PEUs and PDMS-PEU, thus confirming the oxidative stability of the carbonate linkage.
They found that highly hydrophilic polyurethane-polyvinyl pyrrolidone or, in contrast, highly hydrophobic polyurethane-poly methyl methacrylate IPNs elicited inert responses in vivo. The authors concluded that the relative hydrophobicity or hydrophilicity of polymer surfaces is an important factor determining tissue compatibility. They also found that interfacial energy had no correlation with tissue responses whereas an interfacial energy near zero has been shown to be a requirement for blood compatibility.
More recently, Hunt et al further investigated the effect of changing the hydrophilicity of polyurethanes on the in vivo biological response.
After intramuscular implantation, the acute and chronic inflammatory responses were evaluated by counting specific cell types and quantifying cytokines released from these cells. In conclusion, the effect of hydrophilicity, net charge, antioxidant incorporation, and chemical composition on the hemocompatibility, biocompatibility or biostability of PU surfaces is still under debate and requires clear and well-designed studies to bring quantifiable and reproducible parameters that will discriminate between polyurethanes of various chemical composition, structure and morphology.
Effect of Protein Adsorption on Polyurethanes One final thought regarding the hemocompatibility and biocompatibility of polyurethanes is to review the effects, potential benefits or drawbacks of protein adsorption on PU surfaces. Please verify that you are not a robot.
Would you also like to submit a review for this item? You already recently rated this item. Your rating has been recorded. Write a review Rate this item: Preview this item Preview this item. The polyurethanes book Author: David Randall, Ph.
Print book: English View all editions and formats Rating: Subjects Polyurethanes. Polyurethane More like this Similar Items. Find a copy online Links to this item Table of contents Table of contents. Allow this favorite library to be seen by others Keep this favorite library private. Find a copy in the library Finding libraries that hold this item Details Additional Physical Format: Online version: Polyurethanes book. Huntsman Polyurethanes] ; New York: Internet resource Document Type: Steve Lee.
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Free returns on all UK orders download with confidence. No hassle returns.Read full returns policy. Hit a particularly tricky question? In a second study, Li et al were interested in blending phospholipid diols with long chain alkyl groups C16 to C20 because of their claimed blood compatibility, excellent mechanical properties, and nonether soft segment composition.
Please re-enter recipient e-mail address es. With the increasing number of synthetic materials being introduced into the field of medicine, there is an increasing demand for more discriminating tools to evaluate their safety and efficacy. Synthesis of new haemocompatible phospholipid polyurethanes for biomedical applications.
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