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پزشکی، دندانپزشکی و داروسازی
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محصولات
Laser Application of Polymers - Original PDF
نویسندگان: خلاصه: Abstract Laser ablation of polymers has been studied with designed materials to evaluate the mechanism of ablation and the role of photochemically active groups on the ablation process, and to test possible applications of laser ablation and designed polymers. The incorporation of photochemically active groups lowers the threshold of ablation and allows high-quality structuring without contamination and modification of the remaining surface. The decomposition of the active chromophore takes place during the excitation pulse of the laser and gaseous products are ejected with supersonic velocity. Time-of-flight mass spectrometry reveals that a metastable species is among the products, suggesting that excited electronic states are involved in the ablation process. Experiments with a reference material, i.e., polyimide, for which a photothermal ablation mechanism has been suggested, exhibited pronounced differences. These results strongly suggest that, in case of designed polymers which contain photochemically active groups, a photochemical part in the ablation mechanism cannot be neglected. Various potential applications for laser ablation and the special photopolymers were evaluated and it became clear that the potential of laser ablation and specially designed material is in the field of microstructuring. Laser ablation can be used to fabricate three-dimensional elements, e.g., microoptical elements
Alkylene Oxides and Their Polymers - Original PDF
نویسندگان: خلاصه: The poly(alkylene oxide)s are linear or branched-chain polymers that contain ether linkages in their main polymer chain structure and are derived from monomers that are vicinal cyclic oxides, or epoxides, of aliphatic olefins, principally ethylene and propylene and, to a much lesser extent, butylene. These polyethers are commercially produced over a range of molecular weights from a few hundred to several million for use as functional materials and as intermediates. Lower polymers are liquids, increasing in viscosity with molecular weight. The high polymers can be thermoplastic. Solubilities range from hydrophilic water-soluble polymers that are principally derived from ethylene oxide, to hydrophobic, oil-soluble polymers of propylene oxide and butylene oxide. A wide variety of copolymers is produced, both random copolymers and block copolymers. The latter may be used for their surface-active characteristics.
Absorbable biodegradable polymers - Original PDF
نویسندگان: خلاصه: Egyptians sutured wounds as early as 3500 B.C. using a variety of natural polymers including treated intestines, which are the early versions of collagen-based surgical gut sutures.1 Synthetic, absorbable polyesters based on 2-hydroxyacetic acids were developed for preparing less tissue reactive alternatives to surgical gut sutures in the early 1970s. In addition to collagenbased polymers, other natural, absorbable polymers, such as albumin, chitosan, and hyaluronic acid and derivatives thereof have been used for many pharmaceutical and biomedical applications for several decades.2 Of these polymers, the application of chitosan and hyaluronic acid–based polymers has received a great deal of attention in the past 15 years for use in controlled drug delivery systems, tissue repair, tissue engineering, and controlling certain biological events.
Polymers in Electronics Market Report - Original PDF
نویسندگان: خلاصه: Designers of electrical and electronic components have a wide choice of polymers at their disposal - cost is a prime consideration but competition in the market place is imposing ever more stringent specification criteria on the equipment designer who, in turn, is demanding significantly improved performance from his polymer supplier. This report lists the most commonly used polymers with brief notes on their properties. This report seeks to provide an overall picture of the varied use of polymers in the manufacture of electronic components. It has endeavoured to identify trends and future movements of the market. The pattern of polymer usage has changed and material formulations have had to be modified to conform with new European Union (EU) legislation relating to the use of hazardous materials in components. Furthermore there is now far more emphasis on recycling rather than landfill disposal and these are issues covered in the report. This report will be of interest to all those involved in using polymers to produce electronic components and to those who provide the raw materials for the production.
Coatings Of Polymers And Plastics - Original PDF
نویسندگان: خلاصه: Human development is clearly linked to continuous improvements in the materials used every day. Entire stages of history have been named after the critical materials—Stone Age, Bronze Age, Iron Age, and now, the Age of Plastics. When asked his opinion on chemistry’s largest contribution to science and society, Lord Todd, the President of the Royal Society of London, responded: “I am inclined to think that the development of polymerization is, perhaps, the biggest thing chemistry has done, where it has had the biggest effect on everyday life. The world would be a totally different place without artificial fibers, plastics, elastomers,
Handbook of Biodegradable Polymers - Original PDF
نویسندگان: خلاصه: Biodegradable polymers are niche market materials finding focused applications, including agricultural applications such as mulch films, flowerpots and controlled-release fertilisers and packaging items such as carrier bags and food wrapping and containers. They have the potential to provide a solution to a range of environmental concerns: decreasing availability of landfill space, declining petrochemical sources, and also offer an alternative option to recycling. Rapra's Handbook of Biodegradable Polymers is a complete guide to the subject of biodegradable polymers and is ideal for those new to the subject or those wanting to supplement their existing knowledge. The book covers the mechanisms of degradation in various environments, by both biological and non-biological means, and the methods for measuring biodegradation. The degree and rate of biodegradation is dependent on the chemical composition of the polymer and its working environment, and so there is no single optimal method for determining biodegradation. This handbook provides discussion of international and national standards and certification procedures developed to ensure accurate communication of a material's biodegradability between producers, authorities and consumers. The book goes on to consider the characteristics, processability and application areas for biodegradable polymers, with key polymer family groups discussed.
Colloids and interfaces with surfactants and polymers: an introduction - Original PDF
نویسندگان: خلاصه: This text is both an introduction to the field and a bridge to the more specialist texts that are available, and includes recent ideas that have been developed on the interactions between particles and the concentrated state. It covers the fundamentals of colloid and interface science, placing emphasis on concentrated systems and the ideas associated with them. Takes a user-friendly, non-mathematical approach Includes the widely used techniques such as rheology in greater depth than other introductory texts Gives many practical examples of colloid and interface science Provides guidance on how to apply new ideas to a number of different systems
Liquid Crystalline Polymers - Original PDF
نویسندگان: خلاصه: As we know, there are three basic states of matter, solid, liquid, and gaseous states. These states of matter can be transformed into each other at appropriate conditions. In the solid state (generally meaning the crystalline state), the building blocks, such as atoms, or molecules, or clusters of molecules are packed closely and regularly, forming a crystal lattice. The X-ray diffraction of the state shows many regular diffraction spots. Over 95% of matter on the earth exist in the form of the crystalline state. The types of crystal structure are enormous. The physical properties of crystals are basically anisotropic. The crystals have a constant melting temperature (except for amorphous solids).
Natural and Wood Fibre Reinforcement in Polymers - Original PDF
نویسندگان: خلاصه: The use of composite materials dates from centuries ago, when it all started with natural fibres. In ancient Egypt some 3,000 years ago, clay was reinforced by straw to build walls. Later on the natural fibre lost much of its interest. With the industrial use of plastics, combinations of plastics with natural fibres or wood flour were introduced. The body of the East German car ‘Trabant’ (1950-1990) was one of the typical examples for application of natural fibres (cotton) embedded in a polyester matrix.آیا کتاب مورد نظر هنوز بر روی سایت قرار نگرفته است؟ جای نگرانی نیست! کافی است بر روی گزینه سفارش کتاب کلیک کرده و درخواست خود را ثبت کنید. در کمتر از چند ساعت کتاب شما را آماده خواهیم کرد.