Inorganic high polymers  [c.514]















Key properties are improved resistance to heat, light, and weathering. This polymer is unaffected by most detergents, cleaning agents, and solutions of inorganic acids, alkalies, and aliphatic hydrocarbons. Poly(methyl methacrylate) has light transmittance of 92% with a haze of 1 to 3% and its clarity is equal to glass.  [c.1012]

The inclusion of poly (dimethyl siloxane) in Table 1.2 serves as a reminder that polymers need not be organic compounds. The physical properties of inorganic polymers follow from the chain structure of these molecules, and the concepts developed in this volume apply to them and to organic polymers equally well. For example, poly (dimethyl siloxane) shows a very low viscosity compared to other polymers of comparable degree of polymerization. We shall see in Chap. 2 that this is traceable to its high chain flexibility, which, in turn, is due to the high concentration of chain backbone atoms with no substituents. We shall not examine the classes and preparations of the various types of inorganic polymers in this text. References in inorganic chemistry should be consulted for this information.  [c.16]

Inorganic—Organic Hybrids. One of the fastest growing areas la sol—gel processiag is the preparation of materials containing both inorganic and organic components. The reason is that many appHcations demand special properties that pure materials can seldom provide. The combination of inorganic and organic materials is, thus, an attractive way to deUver materials that have desirable physical, chemical, and stmctural characteristics. In this regard, sol—gel chemistry offers a real advantage because its mild preparation conditions do not degrade organic polymers, as would the high temperatures that ate associated with conventional ceramic processiag techniques. The voluminous Hterature on the sol—gel preparation of inorganic—organic hybrids can be found ia several recent reviews (16—20) and the references thereia only a quaUtative sketch is given ia this section.  [c.3]

For strongly interacting systems, chemical bonding can be induced by using functionalized precursors. There are three basic types of precursors inorganically functionalized preformed organic polymers, organically functionalized oxides, and precursors containing both inorganic and organic functional groups. Examples of commonly used precursors are organofunctional metal alkoxides (RO) —E—X—A (19) and bridged polysilsesquioxanes (20). In (RO) —E—X—A, A is a functional organic group and X is a hydrolytically stable spacer linking A and the metal alkoxide which provides the inorganic function. The use of such precursors has allowed the control of very small domain sizes, often in the nanometer range, in the preparation of inorganic—organic materials (16,19,20). The challenge is to achieve a high degree of mixing of the two phases, thus, enabling the manipulation of interfacial properties at a molecular level. Another promising strategy to provide better homogeneity between the two phases is to form the inorganic and organic phases simultaneously, leading to what is known as a simultaneous interpenetrating network (16).  [c.3]

Superabsorbents. Water-sweUable polymers are used extensively in consumer articles and for industrial appUcations. Most of these polymers are cross-linked acryUc copolymers of metal salts of acryUc acid and acrylamide or other monomers such as 2-acrylamido-2-methylpropanesulfonic acid. These hydrogel forming systems can have high gel strength as measured by the shear modulus (134). Sometimes inorganic water-insoluble powder is blended with the polymer to increase gel strength (135). Patents describe processes for making cross-linked polyurethane foams which contain superabsorbent polymers (136,137).  [c.144]

The other main category of textile fibers comprises those fibers manufactured from natural organic polymers, synthetic organic polymers, and inorganic substances. Glass fiber is the only inorganic synthetic fiber ki common use, although other ceramic and metallic fibers are being developed, particularly for use ki high performance fiber-reiaforced composites.  [c.264]

The second flocculation mechanism is lefeiied to as the charge patch oi electrostatic mechanism (32). A highly cationic polymer is adsorbed on a negative particle surface in a flat conformation. That is to say most of the charged groups are close to the surface of the particle, as illustrated in Figure 3. This promotes flocculation by first reducing the overall negative charge on the particle thus reducing interparticle repulsion. This effect is called charge neutralization and is associated with reduced electrophoretic mobiUty. In addition, the areas of polymer adsorption can actually have a net positive charge because of the high charge density of the polymer. The positive regions are also attracted to negative regions on other particles, which is called heterocoagulation. Polymeric inorganic materials may also adsorb on surfaces and cause flocculation by a similar mechanism. A third mechanism is called bridging. Some individual segments of a very high molecular weight polymer, usually a high molecular weight anionic polyacrylamide, adsorb on a surface. As shown in Figure 4a, large segments of the polymer extend into the Hquid phase where other segments are adsorbed on other particles, effectively linking the particles together with polymer bridges. In contrast to the first two mechanisms, bridging is strongly affected by molecular weight and the ionic content of the solution. Only large molecules (33) can bridge between particles. Low molecular weight anionic polymers actually act as dispersants in the same systems. The partial adsorption of the anionic polymer on a negatively charged particle is promoted by the presence of divalent and trivalent ions (34). The charge density of the polymer is also critical. As the negative charge on the polymer increases, the mutual repulsion of negatively charged groups along the chain causes the molecule to have a more extended conformation in solution that favors bridging. The higher charge, however, works against adsorption on negatively charged particles. Increasing the ionic strength of the medium promotes adsorption however, the ions shield the negatively charged groups along the chain, which favors a less extended conformation. For this reason, for each combination of aqueous and soHd phases there is an optimal charge (35). This effect was first reported in 1954 (36). This principle is well illustrated in the Bayer process, where the residue from bauxite leaching is alternately flocculated and repulped in solutions with decreasing ionic content. As the ionic content goes down, the optimal charge, in terms of settling rate, of the anionic polymer used as a flocculant decreases (37).  [c.34]

A fourth mechanism is called sweep flocculation. It is used primarily in very low soflds systems such as raw water clarification. Addition of an inorganic salt produces a metal hydroxide precipitate which entrains fine particles of other suspended soflds as it settles. A variation of this mechanism is sometimes employed for suspensions that do not respond to polymeric flocculants. A soHd material such as clay is deUberately added to the suspension and then flocculated with a high molecular weight polymer. The original suspended matter is entrained in the clay floes formed by the bridging mechanism and is removed with the clay.  [c.34]

Small particles of siUca or clay can also be used in combination with polymers as retention aids. These are called microparticle systems (15). Low molecular weight cationic polymers on the surface of the inorganic particle bind to the fine cellulose fibers by bridging. The soHd particles extend the effective length of the flocculant molecules and give the floes rigidity. These small, rigid floes are bound tightly to the larger fibers. In many systems, more than one of these mechanisms may be operative at the same time. Cationic—anionic combinations are often used in mineral processing and retention aid apphcations. The cationic polymer is usually added first to neutralize the charge on the particles and form charge patches. Alum or ferric salts can also be used for this purpose. These can serve as adsorption sites for higher molecular weight anionic flocculants. For retention aids, a cationic polymer with a moderately high charge density is usually preferred (39). Very small floes are formed which are then flocculated by a higher molecular weight anionic  [c.34]

Chemical Properties. A combination of excellent chemical and mechanical properties at elevated temperatures result in high performance service in the chemical processing industry. Teflon PEA resins have been exposed to a variety of organic and inorganic compounds commonly encountered in chemical service (26). They are not attacked by inorganic acids, bases, halogens, metal salt solutions, organic acids, and anhydrides. Aromatic and ahphatic hydrocarbons, alcohols, aldehydes, ketones, ethers, amines, esters, chlorinated compounds, and other polymer solvents have Httle effect. However, like other perfluorinated polymers,they react with alkah metals and elemental fluorine.  [c.375]

The search for new high performance materials has spurred the development of composites combining high modulus /high thermal stabiUty inorganic glasses and low modulus /low thermal stabiUty polymeric glasses. Research has resulted in a novel class of amorphous polymer—glass composites referred to as organic—inorganic hybrids or inorganic—organic hybrids, depending on the component with the highest volume fraction. These materials are synthesized in a variety of ways but ultimately exhibit near-molecular-level mixing of the matrix and the filler. Hence the term hybrid. Typically, this high degree of mixing results in transparent materials which exhibit significant increases in thermomechanical properties owing to extensive interaction between the polymeric and inorganic phases. However, the relatively high volume fraction of polymer included in these materials normally limits their service temperatures to well below 400°C. One route to promoting mixed, interactive phases is the sol—gel processing of metal alkoxides, which allows the development of an inorganic, oxygen-bridging network during composite consoHdation and promotes the formation of polymeric inorganic glasses with a morphology, and consequentiy a resultant polymer—glass interface, that is a function of the traditional sol—gel processing variables and other controllable factors. In essence, this approach results in materials that can be broadly defined as amorphous, interpenetrating network stmctures.  [c.328]

The successfiil synthesis of a transparent soHd polymer electrolyte (SPE) based on PEO and alkoxysilanes has been reported (41). The material possessed good mechanical properties and high electrical conductivity (around 1.8 x 10 S/cm at 25°C) dependent on the organic—inorganic ratio and PEO chain length.  [c.329]

Manufacturing. The use of advanced textile materials ia manufacturing is a diverse and expanding market. Optical fibers are being increasingly used in telecommunications, computers, cable television, and to faciHtate process control in the nuclear, petrochemical and chemical, and food industries. Although most optical fibers are glass or of related inorganic composition, there are optical fibers for special appHcations comprised of poly(methyl methacrylate), polystyrene, and polycarbonate that are coextmded with fluorinated acrylate polymers. Polyacetal, ie, poly(oxymethylene) fiber has also been used as a reinforcing material for optical fibers. Basic fiber properties required for an optical fiber are (/) a stmcture with a high refractive index core and a low refractive index cladding (sheath bonded to core under high temperature and pressure) (2) fiber with a low attenuation or low power loss of light over distance and (J) fiber with low dispersion or pulse broadening as light travels down the fiber (36).  [c.72]

The most commercially successhil inorganic polymers to date are the polysdoxanes, owing to their unique high temperature stabiUty, low temperature flexibiUty, and a number of other advantageous properties such as low surface energy and room-temperature vulcani ability (see Silicon COMPOUNDS, silicones). Despite the commercial success of polysdoxanes, however, the development of new inorganic polymers has not kept pace with that of their organic counterparts. The principal reasons for this ate that a large variety of inorganic monomers has not been readily available, and extensive research and development with organic polymers have quickly provided many articles of commerce.  [c.256]

Volatile Nitrides. The nitrogen compounds of the nonmetallic elements generally are not very stable. These nitrides decompose at elevated temperatures. Some are explosive and decompose upon shock. They form distinct molecules similar to organic compounds, and at low temperatures are gaseous, Hquid, or easily volatilized soHds. Exceptions are (SN), which is polymeric, chemically stable, and has semimetallic properties and (PNCl2), which has attracted some scientific interest as inorganic mbber (see Inorganic high polymers). None of the volatile nitrides has obtained any substantial industrial appHcation except ammonia (hydrogen nitride) and nitrogen oxide (oxygen nitride). Gaseous nitrogen fluorides are explosive Cl N, a dark-yeUow Hquid, evaporates somewhat on heating and explodes. I NNH [15823-38-8] detonates at the slightest touch.  [c.53]

See Elastopiers.synthetic-phosphazenes Inorganic high polymers.  [c.513]

Other than the obvious advantages of reduced fluorescence and high resolution, FT Raman is fast, safe and requires mmimal skill, making it a popular analytic tool for the characterization of organic compounds, polymers, inorganic materials and surfaces and has been employed in many biological applications [41].  [c.1200]

Solid-state NMR has long been used by physicists to study a wide range of problems such as superconductivity, magnetism, the electronic properties of metals and semiconductors, ionic motion etc. The early experiments mostly used wide line NMR where high resolution was not required but with the development of the teclmique, particularly the improvements in resolution and sensitivity brought about by magic angle spiimmg ( Bl.12.4.3). and decoupling and cross polarization ( B solid-state NMR has become much more widely used tln-oughout the physical and, most recently, biological sciences. Although organic polymers were the first major widespread application of high-resolution solid-state NMR, it has found application to many other types of materials, from inorganics such as aluminosilicate microporous materials, minerals and glasses to biomembranes. Solid-state NMR has become increasing multinuclear and the utility of the technique is evidenced by the steady and continued increase in papers that use the teclmique to characterize materials. There is no doubt that the solid-state NMR spectrometer has become a central piece of equipment in the modem materials physics and chemistry laboratories.  [c.1465]

The goal of constmcting stable organic molecular architectures with desired properties that modify surfaces independent from their bulk characteristics is of fundamental interest in many areas. Organic chemists have made significant progress over recent years in designing and constmcting molecules that have certain desired physical and chemical properties. Assembling such molecules onto surfaces, as well as characterizing and studying the resulting layers, lies at the centre of interest in many laboratories, and a variety of techniques have been employed in order to reach this goal. Ultrathin and especially monomolecular organic films with a high degree of order are of special interest since they open up new fields of research and could establish an organic counteriDart to inorganic crystals. Such films play an important role not only in fundamental science, where they often serve as model systems (e.g. for polymers) but also in applied sciences, where they are employed as corrosion inlribitors, lubricants, adhesion promoters and in biosensors, as well as in many other applications.  [c.2608]

Qualitative direct displacements on a polymer chain are rare, but possible for n = 15, 000 in the example shown in equation 5, due to the high reactivity of the P—Cl bond. Some of the organic groups can be placed on the heterocychc monomer before the ring-opening polymerization if their size is limited to avoid steric influences on the polymerization. The hydrophobic inorganic backbone thus provides an easy route to variable water-solubilizing side nonionic or ionizing groups (Fig. 8). These are stable to hydrolysis at room temperature. The glucosyl (15) and glyceryl (16) species are sensitive to hydrolysis in neutral pH water at 100°C they hydrolyze slowly to phosphate, small amounts of ammonia, and glucose or glycerol when the pH is changed. The methylamino-substituted (17) and the poly(bis(methoxyethyoxy)phosphazene) (MEEP) (18) ate stable to water at neutral and basic pH but ate sensitive to strong acids.  [c.319]

Eor filter belt presses and centrifiiges, resistance to shear and mechanical pressure is the most important parameter. In general, floes produced by charge patch neutralization are stronger than those produced by inorganic salts alone. If these floes are broken, the cationic polymer remains strongly bound to the surface and the floes can reform. Very strong floes can be made with high molecular weight polymers that bridge between particles. However, these may not reform if broken because the bridging segments have been broken. The residual polymer fragments on the surface may even act as a dispersant by covering the particle surface, as shown in Eigure 4b.  [c.35]

Oigaiiic glasses aie amorphous stmctuies with relatively low glass-transition temperatures, T, ie, <400 " C. Theic apphcations are limited to additives such as dyes, stains, and processiug aids for foods, polymers, metals, etc. High molecular weight organic glasses, ie, polymers, are generally associated with plastics. Typically, organic polymer glasses possess low modulae owiag to the low bond energy associated with carbon—carbon bonds. However, a wide variety of properties can be engineered into these materials by variations ia processing, additives, and second-phase reinforcement. Inorganic glasses, on the other hand, which are high energy oxide stmctures that are useful at elevated temperatures (>400° C) have high modulae. Traditionally, a glass can be defined as an inorganic product of fusion which has cooled to a rigid condition without crystallising. However, this definition has become somewhat obsolete. Low temperature synthetic routes, such as the sol—gel process, have been developed which allow the production of high purity, multicomponent inorganic glasses at temperatures significantly less than those required for traditional fusion, ie, much less than 1000°C.  [c.328]

It was expected that the mixed region, the diffuse glass—polymer interface, would be responsible for many of the composites properties. Therefore, more recentiy, methods of modifying the microstmcture of these hybrids in situ have been examined (34,35). It was found that by using a strongly basic solution of ethylamine and water, the solubiUty of siUca at high pH could be used to selectively modify the interface between the organic and inorganic phases. Essentially, syneresis and ripening of the polysiUcate domains just like that experienced for traditional sol—gel-derived inorganic glasses aged at high pH could be induced, resulting in phase separation. This modification resulted in systematic changes in the strength of the hybrid. Additionally, this process has been used in the synthesis of organic—inorganic hybrid interpenetrating networks (IPN). By controlling the degree of interaction (and hence PTMO restriction), the ethylamine procedure was used to control the equiUbrium mass uptake of various vinyHc monomers absorbed by the original hybrid network. Subsequent y-radiation-induced polymerization of this absorbed monomer resulted in the formation of an IPN. Indeed, the properties of the new IPN were a function of the preirradiation, ethylamine exposure processing. These new materials were synthesized using methacrylic acid (MAA), N-vinylpyrrohdinone (NVP) and cyclohexyl methacrylate (CHMA) monomers. In particular, the PMAA and poly(N-vinylpyrrohdinone) (PVP) IPN exhibited hydrogel-hke behavior. This approach opens new potential appHcations for these hybrid glasses.  [c.329]

HoUow-fiber membranes are subjected to extensive studies for gaseous separation (eg, CO2, H2, O2, N2, H2S, CO, CH, where the capiUary configuration has an advantage over the spiral-wound flat film (42) and plate-and-frame devices. Such fibers achieved first niche commercial prominence in such medical purposes as membrane oxygenators. Commerciali2ations and development activities are now occurring rapidly at a number of corporations including A/G Technology, Dow Chemical Co., Du Pont, Monsanto, Perma Pure, Toyobo, Ube Industries, and Union Carbide. For high pressure apphcations it appears glassy rigid polymers as polysulfone, polycarbonate polyaramid, and polyamide are preferred. Sintered inorganics, ie, iron, nickel, aluminas, and carbides are involving much attention. Glassy polymers have an amphorous polymeric material that is below its softening or glass-transition temperature under the conditions of use. This concept is opposed to a mbber polymer which is employed above its glass-transition temperature. The rigidity of the glassy polymers offer better selectivity than the mbbery polymers (24).  [c.155]

The most common means of controlling galvanic attack on magnesium is through minimising the electrochemical potential difference between the magnesium and the other metal. For steel fasteners, tin, cadmium [7440-43-9] and sine electroplates have long been recognised for their abdity to reduce the galvanic attack induced by the fastener when compared to bare steel The relative effectiveness of these electroplates has generally been accepted to be in descending order as Hsted. Not ad. methods of deposition are equivalent, however. Certain proprietary sine- and aluminum-fdled polymers, as wed as some ion vapor deposited aluminum coatings, appHed to steel fasteners may actuady produce more damage than the untreated steel fastener itself. This has been attributed to two possible causes either the high surface area involved with each of the particulate coatings, or the contamination of the particulate surface with active cathodic contaminants such as iron, nickel, or graphite. Another point of interest is that a simple inorganic chromate treatment appHed to a cadmium or 2inc electroplate, used to preserve its brightness, has been found as effective in further retarding the galvanic attack on magnesium as was a coating of epoxy resin. This is consistent with the known inhibitive effects of chromate on the cathodic reduction process and has been observed with other fastener coatings as wed (133—135).  [c.334]

See pages that mention the term INORGANIC HIGH POLYMERS : [c.108]    [c.318]    [c.263]    [c.375]    [c.179]    [c.322]    [c.18]    [c.218]    [c.329]   
See chapters in:

Encyclopedia of chemical technology volume 14  -> INORGANIC HIGH POLYMERS