Application medical

The medical sector is the fourth largest consumer of plastics after the packaging, construction, and automotive sectors. It has a relatively high growth rate (8%/year). The growth is in part due to our longer life expectancy but also by new technological advances in medicine. 

As is evident from the conducted studies, the majority of problems within this sector are veiy typical of the plastic industry in general. These include the need to improve reinforcement, durability, fatigue resistance, adhesion, reduce water absorption, etc. In addition to these problems are some issues which are only related specifically to medical applications such as toxicity and biocompatibility. These issues make this research an exclusive field in which the publication of findings is 

Most material studies reported in medical journals are of interest to those involved in mainstream plastic applications. Some medical plastics must perform under constant water immersion. It was reported that absorption of 1 % water reduces the fatigue life of PMMA by a factor of four, since bone cement can only be replaced by a surgical operation such a performance is clearly unacceptable. The use of silane to treat the hydroxyapatite filler in this material reduced water uptake. The water uptake increased with increased concentration of hydroxyapatite. In applications, such as dental fillings, increased water uptake is considered helpful since it compensates for the loss of volume due to shrinkage of the filling during curing. 

In hard tissue replacement, polyurethane filled with hydroxyapatite is used. The composite must have high strength and stiffness and excellent creep and fatigue resistance. The material in the study met these requirements when hydroxyapatite was pretreated with hexamethylene diisocyanate. The treatment improved the adhesion between the matrix and the filler.  

The durability of cemented joint replacements depends on the properties of PMMA bone cement. A titanium fiber was used to reinforce the cement. Before the cement was applied it was centrifuged to remove entrapped air which would cause voids in the connection. The treatment also improved the ductility of the cement. Similar processes are used in many plastic industries to improve elastic properties. 

In a wide variety of medical devices, Parylenes are used, mainly as protective coatings. In Table 2.5 some devices are summarized. 

The variability in functional groups that can be prepared by CVD polymerization opens the field of surface engineering of microfluidic devices. Insulin has been immobilized on CVD-coated surfaces in order to enhance the attachment and the growth of cells under in vitro conditions. Copolymers with amino-p-xylylene and p-xylylene moieties bear pendant amino groups that may act as anchors for functionalization. 

These amino groups can be used for the immobilization of thrombin inhibitors such as R-hirudin. The functionalization is useful for devices that are in contact with native blood. A potential field of applications is stents with reduced restenosis, i.e., a reduced tendency of blocking the blood flow.  

Parylene C Specialty Coating Systems (SCS) Chlorinated type 

First results of the use of water jets for medical applications have been pubhshed in 1982 - a plain waterjet scalpel for the resection of liver tissue has been appUed [62]. The use of the plain waterjet offers an important advantage over conventional surgery and ultrasound or laser cutting athermic and selective cutting - the plain waterjet under low pressure (below 100 bar) cuts the tissue but the blood vessels are not injured, because they are slightly more resistant There are several other possibilities to exploit the potential of the plain waterjet in medicine, such as 

However, in medical applications the waterjet technology is actually limited to soft tissue cutting - the plain waterjet has not enough cutting performance to be applied 

Kocanda, A. and Sadlowska, H. (2008) Automotive component development by means of hydroforming a review. Arch. Civil Mech. Eng., 8 (3), 55-72. 

and Wu, P. (2009) Optimization for loading paths of tube hydroforming using a hybrid method. Mater. Manuf. Process., 24 (6), 700-708. 

and Lin, Z,Q, (2008) Loading path prediction for tube hydroforming process using a fuzzy control strategy. Mater Des., 29 (6), 1110-1116. 

Xhe medical market consists of several different types of apphcations. Xable 13.14 summarizes some of the performance criteria and applications. 

Blends and alloys that are most appropriate for the above apphcations include PPE/PS and PC/ABS on the lower to mid performance end, with PEI blends at the high end. For obvious reasons, FDA compliance is critical. Most apphcations of blends and alloys in medical devices are best suited to the impact and toughness performance profiles of amorphous systems. Since many of the applications require clarify and transparency, PC is one of the most widely used resins. 

One of the most important performance criteria for medical applications is that of autoclaving. This is a common method to sterilize instruments and devices that uses a combination of high pressure and steam. In an aggressive cyclic environment such as this, retention of impact properties and optical properties is important. Another essential sterilization technology that is less severe than autoclaving is the use of ethylene oxide, against which blends and alloys must display chemical resistance. 

Gamma radiation is growing as an accepted alternative to ethylene oxide sterilization. Although it is cleaner than ethylene oxide in that it does not leave any residue, there is a tendency for resins to discolor or turn yellow. 

PAB s are also used in applications employing chemical vapor sterilization. This sterilization process, common in dental applications, uses an 

Because of their inertness and relative purity, some fluoroplastics (e.g., certain grades of PTFE) are used in medical applications. In such cases, the U.S. Food and Drug Administration (FDA) most often reviews and approves the entire medical device, not its components, such as specific parts or resin used. Resin suppliers have strict specific policies about the use of their resins in medical devices [5], 

Reliability. The performance ofthe electronic devices implanted in the body is extremely important. Malfunctioning can result in death. For hybrid microcircuits and multichip modules, the qualification tests and accelerated tests required of military and space applications also apply, although some shock and vibration tests are not realistic for humans. In addition, the Food and Drug Administration (FDA) becomes involved in testing and reviewing 

For externally used diagnostie eleetronics, reliability may also be alife-or-death situation if instruments do not provide accurate information. 

Some adhesives suppliers already have test data showing compliance of their adhesives to ISO-10993 and will provide a certificate of compliance for their products. However, passing the ISO or USP Class VI tests should be considered a starter in proving that an adhesive has a low level of toxicity it does not guarantee FDA approval. The FDA often requires more extensive testing. 

Sterilization. All devices implanted in the body or that come into contact with body fluids or blood must be sterilized and be resistant to the sterilization conditions. Adhesive-bonded parts are notused in direct contact with the body fluids. They are generally part of an electronic module that is hermetically sealed or otherwise encapsulated or shielded. However, the sterilization conditions for the module must not degrade the internal adhesive-attached components. Some adhesives such as cyanoacrylates and UV-cured acrylics degrade at the elevated temperatures and high humidity 

Gaseous ethylene oxide (EtO). Exposure to ethylene oxide, admixed with a carrier gas such as carbon dioxide or a chlorofluorocarbon, is the most widely used sterilization process because it has the least damaging effect on materials and devices and is low cost. EtO sterilization is a room-temperature process that affects only the external surfaces of a module. 

During the past two decades significant advances have been made in the development of biodegradable polymeric materials for biomedical applications. The recent trends, applications and materials have been reviewed (1,2). 

Degradable pol mieric biomaterials for medical applications are particularly preferred for (1)  

Materials intended for use inside the body have to be approved by regulatory agencies. The minimal requirements of biomaterials for medical applications include nontoxicity, effectiveness, and sterilizability (Table 27.1). Although many currently available biomaterials meet these requirements, most of them lack biocompatibility. 

Biocompatibility is the ability of a biomaterial to perform with desired response(s) in a target application. In other words, it cannot be defined in terms of the material properties alone, but it is a combination of the material properties and the function for which it is intended. A variety of materials have been tested as medical devices, which include polymers, metals, ceramics, and their composites. These medical devices can be divided into two groups biodegradable and nonbiodegradable. 

Poly(lactic acid) Synthesis, Structures, Properties, Processing, and Applications, edited by R. Auras, L.-T. Lim, S. E. M. SeUce, and H. Tsuji Copyright 2010 John Wiley Sons, Inc. 

Sterilizable Autoclaving, dry heating, ethylene oxide gas, irradiation, and so on 

Therefore, there is no necessity for a secondary operation to remove them after the defect site is repaired. 

PHAs have been studied as a biomaterial for scaffolds in tissue engineering of both hard and soft tissues. Encapsulation of drugs in controlled drug delivery using PHAs as a matrix material has also been carried out. In addition, PHAs like P(3HB), P(4HB), P(3HB-co-3HHx) have also been used for making medical devices. 

Three leaflets of porous P(3HO) were sutured into the conduit proximal view, (b) Gross appearance of tissue-engineered seeded conduit 24 weeks in vivo (distal view). Clear separation of all three leaflets from the conduit wall is shown, (c) Gross appearance of tissue-engineered unseeded conduit 4 weeks in vivo (proximal view).  

Using this technique, P(3HO) and P(4HB) could be moulded into a complete 3-leaflet valve scaffold without the need for suturing.Novel hybrid valves which were fabricated from decellularized porcine aortic valves and coated with P(3HB-co-3HHx) were also developed. The results in vivo indicated that the P(3HB-co-3HHx) coating reduced calcification and promoted the repopulation of the hybrid valve with the recipient s cells, resembling native valve tissue. 

Inulin is used in an important test for renal failure called the inulin clearance method (Gretz et al., 1993 Chiu, 1994). As inulin is neither secreted nor reabsorbed in the kidney, it can be administered by injection to measure glomerular filtration rate. The relative amounts of inulin in the plasma and urine give an indication of renal function. 

PS/PIB/PS block copolymers have been shown to be vascularly compatible. When loaded with paclitaxel and coated on a coronary stent, the composite can deliver the drug directly to arterial walls. 

Modulation of the drug release behavior from this polymer can be achieved by varying the drug/polymer ratio, by blending the basic block copolymer with other polymers, and by derivatizing the styrene end blocks. In this way, the hydrophilicity of the copolymer is varied (27). 

DNA microarrays have been a very useful genomic tool for the identification of molecular markers for pathological conditions. Peptide and chemical microarrays have proven to be an emerging but very useful tool in proteomies and in the identification and optimization of drug leads and development of diagnostics. In the near future, it is likely that many diagnostic tests will be performed in a microarray format suitable for personalized medicine.  

Solventbome wood preservatives eontain mainly nonpolar, organie solvents apart from other substanees sueh as fungieides and inseetieides. These solvents are elassified as VOCs. 

Solvent-based wood preservatives show several advantages, espeeially in their applieation and teehnieal effeetiveness. They ean be applied repeatedly and do not alter the strueture of the wood produets. Applieation is faster and the eharaeteristies of the final produet are improved, e.g., visual appearanee of surfaee. 

Nevertheless, there are some disadvantages, espeeially environmental ones. Most solvents are released quiekly (VOCs) and ean eause severe environmental effeets. This is espeeially true if toxie solvents are employed. 

Emissions of solvents from wood produets are deseribed under various eonditions, e.g. indoor air emissions from furniture or emissions in test ehambers. Solvents ean be emitted as primary or reaetive produets of the wood produet or the eoating system solvents ean also be investigated as seeondary emission produets.The emission eharaeteristies depend on solvent properties and surrounding eonditions, e.g., air veloeity and air exehange rate.  

In the indoor air, solvents from wood produets follow various pathways. Examples of interaetions are possible reaetions of solvents (e.g., styrene) with air eomponents (e.g., hydroxy radieals), transport into and through indoor materials or sorption proeesses. The emitted solvents ean be redueed by ventilation proeesses or they may be absorbed by organisms. 

Solventbome wood preservatives contain mainly nonpolar, organic solvents apart from other substances such as fungicides and insecticides. These solvents are classified as 

A combination of DEHP and epoxidised soya bean oil is said to be fairly resistant to irradiation, and butyryl-n-trihexyl citrate is reported to be a safe alternative to DEHP for storing red blood cells in PVC bags, at least for limited periods. 

The FRRPP process has been proposed to generate multifunctional membranes that can be employed in HEMFCs. The same type of halogenated multifunctional polymer membranes can be used, but tailor-made for this application. 

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Computed radiography with Luminescence Imaging Plates (IP) has become a routine method in medical applications. It is a new medium for filmless radiography. Since the last five years several tests were performed to check this method for industrial NDT [1-3]. ASTM already issued a proposal for a standard. 

Sharper focusing will extend the use of the MCB tubes to imaging systems in low-power NDT and medical applications. 

The laminography method was developed initially for medical applications as a non-computer layer-by-layer visualization of the human body [1,2]. In this case an inclined initial X-ray beam projects an image of a specific layer of the object to the detector surface with defocusing of the other layers during a synchronous rotation of the object and the detector (Fig. 1). 

In an interesting medical application, the formation of a stable black foam film from amniotic fluid can be used as an assessment of fetal lung maturity [206]. 

Liquid helium s use in magnetic resonance imaging (MRI) continues to increase as the medical profession accepts and develops new uses for the equipment. This equipment has eliminated some need for exploratory surgery by accurately diagnosing patients. Another medical application uses MRE to determine (by blood analysis) whether a patient has any form of cancer. 

J. Thunry, Microwaves Industrial, Scientific and Medical Applications, Artech House, Boston, Mass., 1992. 

V. Kudela, in J. I. Kroschwitz, ed., Foljmers Fiomaterials and Medical Applications Encyclopedia Reprint Series, John Wiley Sons, Inc., New York, 1989. 

Rimplast Petrarch Systems blend medical applications... 

Dialysis and Hemodialysis Historically, dialvsis has found some industrial use. Today, much of that is supplanted by iiltrafiltration, Donan dialysis is treated briefly under electrodialysis. Hemodialysis is a huge application for membranes, and it dominates the membrane field in area produced and in rnonetaiv aliie. This medical application is omitted here. 

The second method for mixture analysis is the use of specialized software together with spectral databases. We have developed a mixture analysis program AMIX for one- and multidimensional spectra. The most important present applications are the field of combinatorial chemistry and toxicity screening of medical preparations in the pharmaceutical industry. An important medical application is screening of newborn infants for inborn metabolic errors. 

Polymers of this type find application in toys and housewares and are of interest for medical applications and a wide variety of miscellaneous industrial uses. 

The thermoplastic elastomer polyamides have found use in conveyor and drive belts, ski and soccer shoe soles, computer keyboard pads, silent gears in audio and video recorders and cameras, and thin film for medical applications. 

Silicone mbbers have been widely used for medical applications, particularly for body implants in structural cosmetic surgery. One high-profile application has been that of breast implants, but the award in early 1994 of enormous damages by a US court in respect of faulty implants may discourage development of this application. 

Whilst approximately twice the raw material cost of TPO- and S-B-S-type polymers, thermoplastic polyurethane elastomers find applications where abrasion resistance and toughness are particular requirements. Uses include gears, timing and drive belts, footwear (including ski boots) and tyre chains. Polyether-based materials have also achieved a number of significant medical applications. There is also some minor use as hot melt adhesives, particularly for the footwear industry. 

Selected physical properties of oxygen are included in Table 9.24. It is a colourless, odourless and tasteless gas which is essential for life and considered to be non-toxic at atmospheric pressure. It is somewhat soluble in water and is slightly heavier than air. Important uses are in the steel and glass industries, oxyacetylene welding, as a chemical intermediate, waste-water treatment, fuel cells, underwater operations and medical applications. 

Polymethyl Methacrylate (PMMA), This material has exceptional optical clarity and resistance to outdoor exposure. It is resistant to alkalis, detergents, oils and dilute acids but is attacked by most solvents. Its peculiar property of total internal reflection is useful in advertising signs and some medical applications. 

In view of increasing interest in the medical applications of curare attention is being given to the elimination of inert material and the provision of a more uniform product. Of primary importance in this... 

The final steps to a synthetic blood depend completely upon good chemistry tailored to meet the exact needs of the body Fluorocarbons, such as perfluorodecalin, recently have been found to induce hypennflated lungs when given either intravenously as an emulsion or mtratracheally as a neat liquid [18, 19] But this and other physiological side effects are now understood, and research is well advanced to prevent undesirable side effects in medical applications of fluorocarbon liquids... 

Using MRI as a substitute for X-ray tomography is only the first of what are many medical applications. More lie on the horizon. If, for example, the rate of data acquisition could be increased, then it would become possible to make the leap from the equivalent of still photographs to motion pictures. One could watch the inside of the body as it works— see the heart beat, see the lungs expand and contract—rather than merely examine the structure of an organ. 

Purification of poloxamers has been extensively investigated due to their use in medical applications, the intention often being to remove potentially toxic components. Supercritical fluid fractionation and liquid fractionation have been used successfully to remove low-molecular weight impurities and antioxidants from poloxamers. Gel filtration, high-performance liquid chromatography (HPLC), and ultrafiltration through membranes are among the other techniques examined [5]. 

The reduced symmetry of the chromophore, which still contains 187t-electrons and is therefore an aromatic system, influences the electronic spectrum which shows a bathochromic shift and a higher molar extinction coefficient of the long-wavelength absorption bands compared to the porphyrin, so that the photophysical properties of the chlorins resulting from this structural alteration render them naturally suitable as pigments for photosynthesis and also make them of interest in medical applications, e.g. photodynamic tumor therapy (PDT).2... 

In medical applications some important biological properties - immunogenic, anti-tumour and anti-viral - can be exploited, as well as the established functional properties based on rheology and gel formation. 

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