Upper and lower conical headers 17 and 16 are fixedly secured to the opposite ends of the housing 11 by means of covers 18 threadably engaged on the housing ends, respectively. PVC is a thermoplastic polymer. Аукцион Proper handling and storage is key to preserving old books. Motorcraft Toyota
Перейти к основному контенту. Включить описание. Состояние показать все. Новый Не указано Введите действительный ценовой диапазон. Формат покупки показать все. The acetylene so generated is then converted to VCM which usually involves the use of a Mercury based catalyst. The process is also very energy intensive with much waste generated. The polymers are linear and are strong. The monomers are mainly arranged head-to-tail, meaning that there are chlorides on alternating carbon centres.
PVC has mainly an atactic stereochemistry , which means that the relative stereochemistry of the chloride centres are random. Some degree of syndiotacticity of the chain gives a few percent crystallinity that is influential on the properties of the material.
The presence of chloride groups gives the polymer very different properties from the structurally related material polyethylene. The product of the polymerization process is unmodified PVC.
Before PVC can be made into finished products, it always requires conversion into a compound by the incorporation of additives but not necessarily all of the following such as heat stabilizers, UV stabilizers, plasticizers, processing aids, impact modifiers, thermal modifiers, fillers, flame retardants, biocides, blowing agents and smoke suppressors, and, optionally, pigments.
Most vinyl products contain plasticizers which dramatically improve their performance characteristic. The most common plasticizers are derivatives of phthalic acid. The materials are selected on their compatibility with the polymer, low volatility levels, and cost.
These materials are usually oily colourless substances that mix well with the PVC particles. The assessment of potential risks related to phthalates, and in particular the use of DEHP in PVC medical devices, was subject to scientific and policy review by the European Union authorities, and on 21 March , a specific labeling requirement was introduced across the EU for all devices containing phthalates that are classified as CMR carcinogenic, mutagenic or toxic to reproduction.
Liquid mixed metal stabilisers are used in several PVC flexible applications such as calendered films, extruded profiles, injection moulded soles and footwear, extruded hoses and plastisols where PVC paste is spread on to a backing flooring, wall covering, artificial leather. Liquid mixed metal stabiliser systems are primarily based on barium, zinc and calcium carboxylates.
In general liquid mixed metals like BaZn, CaZn require the addition of co-stabilisers, antioxidants and organo-phosphites to provide optimum performance.
BaZn stabilisers have successfully replaced cadmium-based stabilisers in Europe in many PVC semi-rigid and flexible applications. In Europe, particularly Belgium, there has been a commitment to eliminate the use of cadmium previously used as a part component of heat stabilizers in window profiles and phase out lead-based heat stabilizers as used in pipe and profile areas such as liquid autodiachromate and calcium polyhydrocummate by According to the final report of Vinyl  cadmium was eliminated across Europe by This is confirmed by the corresponding growth in calcium-based stabilizers, used as an alternative to lead-based stabilizers, more and more, also outside Europe.
Tin-based stabilizers are mainly used in Europe for rigid, transparent applications due to the high temperature processing conditions used. The situation in North America is different where tin systems are used for almost all rigid PVC applications. Tin stabilizers can be divided into two main groups, the first group containing those with tin-oxygen bonds and the second group with tin-sulphur bonds.
One of the most crucial additives are heat stabilizers. Once dehydrochlorination starts, it is autocatalytic. Many diverse agents have been used including, traditionally, derivatives of heavy metals lead, cadmium. Increasingly, metallic soaps metal "salts" of fatty acids are favored, species such as calcium stearate. The choice of the best heat stabilizer depends on its cost effectiveness in the end use application, performance specification requirements, processing technology and regulatory approvals.
PVC is a thermoplastic polymer. Its properties are usually categorized based on rigid and flexible PVCs. PVC has high hardness and mechanical properties. The mechanical properties enhance with the molecular weight increasing but decrease with the temperature increasing. The linear expansion coefficient of rigid PVC is small and has good flame retardancy, the limiting oxygen index LOI being up to 45 or more.
As a thermoplastic, PVC has an inherent insulation that aids in reducing condensation formation and resisting internal temperature changes for hot and cold liquids. PVC is a polymer with good insulation properties, but because of its higher polar nature the electrical insulating property is inferior to non polar polymers such as polyethylene and polypropylene.
Since the dielectric constant, dielectric loss tangent value, and volume resistivity are high, the corona resistance is not very good, and it is generally suitable for medium or low voltage and low frequency insulation materials. PVC is chemically resistant to acids, salts, bases, fats, and alcohols, making it resistant to the corrosive effects of sewage, which is why it is so extensively utilized in sewer piping systems.
For example, PVC is resistant to fuel and some paint thinners. Some solvents may only swell it or deform it but not dissolve it, but some, like tetrahydrofuran or acetone, may damage it. The most common type of gasket utilized in North America is a metal reinforced elastomer, commonly referred to as a Rieber sealing system. However, it must be carefully installed and bedded to ensure longitudinal cracking and overbelling does not occur. Additionally, PVC pipes can be fused together using various solvent cements, or heat-fused butt-fusion process, similar to joining high-density polyethylene HDPE pipe , creating permanent joints that are virtually impervious to leakage.
In February the California Building Standards Code was updated to approve the use of chlorinated polyvinyl chloride CPVC pipe for use in residential water supply piping systems. CPVC has been a nationally accepted material in the U. The Department of Housing and Community Development prepared and certified an environmental impact statement resulting in a recommendation that the commission adopt and approve the use of CPVC. PVC is commonly used as the insulation on electrical cables such as teck ; PVC used for this purpose needs to be plasticized.
Flexible PVC coated wire and cable for electrical use has traditionally been stabilised with lead, but these are being replaced with calcium-based systems. While hydrogen chloride fumes can also pose a health hazard in their own right, it dissolves in moisture and breaks down onto surfaces, particularly in areas where the air is cool enough to breathe, and is not available for inhalation. PVC is a common, strong but lightweight plastic used in construction. It is made softer and more flexible by the addition of plasticizers.
In the U. Other uses include fascia , and siding or weatherboarding. Без марки 4, Гарантия показать все. Без гарантии 27, Гарантийный срок не указан 7, Состояние показать все. Новый , Восстановлен продавцом Для разборки на запчасти или в нерабочем состоянии Не указано Введите действительный ценовой диапазон.
Формат покупки показать все. Купить сейчас , Находится показать все. По умолчанию. Только США. Северная Америка. Параметры доставки показать все. Бесплатная международная доставка. Показать только показать все. Возврат товаров принимается. Уполномоченный продавец. Завершенные объявления. The term "critical surface tension" is a measure of the wettability of a solid mass on its surface.
The solid is wettable with a liquid having a lower surface tension than the critical surface tension of the solid. Preferred examples of the filling liquid include water, glycerine, ethylene glycol, diethylene glycol, aqueous ethanol, aqueous isopropyl alcohol, etc. In introducing the filling liquid, favorable results are obtained by introducing the filling liquid under a pressure of about 0. As described in the foregoing, the oxygenator of the invention has several benefits over prior art oxygenators using conventional porous hollow fiber membranes, including little plasma leakage in extended operation, high production efficiency, size reduction, cost reduction, and improved gas exchange efficiency due to the substantial absence of a silicone layer on the side wall of the hollow fiber membranes.
Particularly when a silicone compound used is a blend of a silicone rubber with a silicone oil, the carbon dioxide removal capacity is noticeably improved over the use of a silicone rubber alone. When the silicone rubber used is a silica-free room temperature vulcanizable silicone rubber, the resulting hollow fiber membranes are effective in preventing thrombus. Further, by strictly controlling the O 2 Flux through the silicone-filled micropores and the total weight of the silicone compound filling in micropores in the hollow fiber membranes, little plasma leakage occurs and sufficient carbon dioxide removal capacity is maintained even after extended circulation of blood.
As a result, there is obtained an oxygenator having reduced dimensions, high gas-exchange efficiency, and high productivity in low cost. According to the manufacturing process of the present invention, porous hollow fibers having micropores open are bundled and assembled in a housing to produce an oxygenator module before they are impregnated with a silicone compound.
A relatively simple apparatus may be used in the impregnating step, leading to a reduced manufacture cost. As compared with an oxygenator unit assembled after hollow fibers are impregnated with a silicone compound, the present process provides an oxygenator without the problem of poor bond in the potting portions due to poor bondability of silicone. The substantially uniform formation of silicone fillings or coatings substantially in micropores eliminates clogging of the hollow fibers to allow for improved blood circulation.
If the impregnating and cleaning steps are conducted with the membrane exterior or interior filled with a predetermined filling liquid, the deposition of the silicone compound on the outer or inner wall of the hollow fiber membranes is minimized and the total weight of the silicone compound filled can be precisely controlled, both leading to stable performance. An oxygenator designated module A as shown in FIG. A silicone compound solution was passed through the blood flow path in module A to impregnate the fibers with the solution for 3 minutes as shown in FIGS.
Thereafter, air was passed through the flow path in module A and a cleaning liquid was then passed along the inner and outer surfaces of the fibers. There was obtained a hollow fiber membrane type oxygenator designated module C wherein only the micropores in the hollow fibers were substantially filled with the silicone compound. The blood contained 12 g hemoglobin per deciliter. The oxygenating and carbon dioxide CO 2 removal capacities of the module were evaluated by operating the module at a predetermined flow rate of blood or oxygen.
Curve C in FIG. The amount of plasma leaked is plotted as a function of circulation time to give curve C in FIG. Using an oxygenator in the form of module A in Example 1 in which the hollow fiber micropores remained open and were not filled with a silicone compound, tests were conducted by the same procedures as in Example 1.
The results are similarly plotted in FIGS. An oxygenator designated module B was manufactured which was similar to module A in Example 1 except that hollow fibers of silicone were used. Using this module B, tests were conducted by the same procedures as in Example 1. As seen from FIG. Extracorporeal circulation tests were conducted through module D of this example and module C of Example 1 using rabits.
The number of platelets in circulating blood was measured at given time intervals. The percent variation of platelet number is plotted with time in FIG. The fibers had a total membrane area of 1. A silicone compound solution was passed through the blood flow path in the module to impregnate the fibers with the solution for 3 minutes. Thereafter, air was passed through the flow path in the module and a cleaning liquid was then passed along the inner and outer surfaces of the fibers.
There was obtained hollow fiber membrane type oxygenators designated modules E to I wherein only the micropores in the hollow fibers were substantially filled with the silicone compound. The results are shown in Table 1. The results are shown in FIG. Module E was practically insufficient in CO 2 removal. The amount of plasma leaked is plotted as a function of circulation time in FIG. Plasma leaked in modules G and H, but to a physiologically neglectable extent.
Curves G and H reached plateaus beyond which plasma leakage did not increase. No leakage of plasma occurred in modules E and F. The fibers were impregnated with a silicone compound of a RTV silicone rubber and a silicone oil in solution form followed by curing.
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