Polymers and Lubricants

The main synthetic route to CFC, HCFC and Halons is the Swarts fluorination. Technically this is often achieved by reaction of a chlorinated or brominated precursor with anhydrous hydrofluoric acid in the presence of a solid Lewis acid catalyst, for example chromia. Other important reactions are Lewis acid-catalyzed halogen isomerization and hydrogenolysis of chlorine or bromine. 

Powell, Applications in Houben-Weyl Organo-Fluorine Compounds (B. Baasner, H. Hage-mann, J. C. Tatlow eds.), Vol. E 10a, Georg Thieme Verlag, Stuttgart, 2000, pp. 59-69. 

A second problem is the tendency of PTFE to creep under applied pressure, which limits the mechanic stability of PTFE devices. This can be overcome to some extent by blending PTFE with filler materials, such as glass or carbon. Also the otherwise highly advantageous anti-stick properties of PTFE cause pro- 

Polymers with elastomeric properties have been obtained since the 1960s by copolymerization of tetrafluoroethylene vith trifluorovinyl ethers such as heptafluoropropyl trifluorovinyl ether (PPVE). These so-called second-generation fluoropolymers combine high thermal and chemical resistance with elasticity and are used for coatings, seals, and other parts which can be produced by conventional extrusion and molding processes. 

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Dispersions of finely divided solids in non-aqueous media have been important for paints, inks, reinforced polymers and lubricating oils, but with the development of liquid toner systems and "ultra-structure" processing of ceramics as fine powders dispersed in organic media, the understanding and optimization of such systems is more important than ever. 

Maleic anhydride CAS. 108-3I-6. til, maleic acid [CAS 110-16-7]. (2), and I umarie acid [CAS 110-17-81. i3) are multifunctional chemical intermediates that lind applications in nearly every Held id industrial chemistry. Each molecule contains two acid carbonyl groups and a double bond in the u. position. Maleic anhydride and maleic acid are important raw materials used in the manufacture of phthalic-type alkyd and polyester resins, surface coatings, lubricant additives, plasticizers. copolymers, and agricultural chemicals [see Alkyd Resins Polymers, and Lubricant). Both chemicals derive their common names from naturally occurring malic acid. 

Recent years have seen the implementation of many various elementorganic compounds in economy. Their applications have proved to be extraordinarily wide for stereospecific polymerisation of olefines, for stabilisation of polymer and lubricant materials, as antiknock additives and additives for engine fuels, as antiseptics, pesticides and so on. 

When the shear-stress viscosity relation of the fluid does not obey the simple newtonian expression of Eq. (5-1), the above equations for free-convection heat transfer do not apply. Extremely viscous polymers and lubricants are examples of fluids with nonnewtonian behavior. Successful analytical and experimental studies have been carried out with such fluids, but the results are very complicated. The interested reader should consult Refs. 48 to 50 for detailed information on this subject. 

The same is true of antioxidants like BHT (butylhydroxytoluene). Although it is used in purified form in human and animal food, its more common use is as a stabilizer for polymers and lubricants. Only BHA (butylhydrox-yanisole), a-tocopherol (vitamin E), TBHQ (tertiary-butylhydroquinone) and propylgal-late, which are marketed by Eastman Kodak, can be considered as purely food antioxidants for the two reasons that they are not toxic and that they are high priced. In fact, Eastman Kodak is the only chemical leader to produce an extended range of food additives mono-and diglycerides and vitamins. 

To analyze such thermodynamic relations of different molecules, we will take the model system to be a homologous series of normal alkanes and alkenes, as very reliable and accurate data are available in the literature. Linear hydrocarbon chains, n-alkanes, are among the most common blocks of organic matter. They form part of the organic and biological molecules of lipids, surfactants, and liquid crystals and determine their properties to a large extent. As major constituents of oils, fuels, polymers, and lubricants, they also have immense industrial importance. Accordingly, their bulk properties have been extensively studied. 

U.S. Pat. No. 3,943,079 (March 9, 1976). P. Hamed. Discontinuous cellulose fiber treated with plastic polymer and lubricant. 

Extrusion pressure is a function of the molecular weight of the polymer and lubricant content of the preform for a given reduction ratio. The higher the molecular weight, the higher the extmsion pres-... 

Henkel Corporation, Emery Group (use of tallow, preparation and testing of soaps, polymers, and lubricants) ... 

Lubricants which are less soluble or incompatible with the base polymer provide external lubrication in the molten phase. In this case the bond strength between polymer and lubricant is weak and under high shear the lubricant is, in effect, squeezed out of the compound. Thus, the lubricant provides external lubrication by covering the surfaces of the processing equipment, reducing friction at the interface of the polymer and the metal surfaces of the machinery. 

Sulfiir-containing compounds are used as components of antioxidative polymer and lubricant additives. The mechanism of their retardation effect was intensively studied in the seventies and turned out to be rather complicated. In this mechanism, the reaction of these compounds with hydroperoxides occn>ies the central place. In 1945, G. Denison was first to show that dialkyl sulfides are oxidized by hydroperoxides to sulfoxides, the latter are oxidized to sulfones... 

Metal complexes, first of all, dialkyl dithiophosphates and dialkyl dithiocarba-mates of such metals as Zn, Ni, Ba, and Ca, are widely used for the stabilization of polymers and lubricants. Inhibitors of this type are inferior to phenols in efficiency at moderate temperatures (350-400 K) but exceed them at higher temperatures (430-480 K). The mechanism of action of inhibitors of this type is complicated. The reaction of these inhibitors with hydroperoxide plays a very important role in the complex mechanism of inhibition. 

The dry-extmsion process consists of four operations dissolution of the polymer in a volatile solvent filtration of the solution to remove insoluble matter extmsion of the solution to form fibers and lubrication, yam formation, and packaging. 

Uses. Neopentyl glycol is used extensively as a chemical intermediate in the manufacture of polyester resins (see Alkyd resins), polyurethane polyols (see Urethane polymers), synthetic lubricants, polymeric plasticizers (qv), and other polymers. It imparts a combination of desirable properties to properly formulated esterification products, including low color, good weathering and chemical resistance, and improved thermal and hydrolytic stabiUty. 

Rigid Applications. The use of the lead stabilizers is very limited in the United States but, they are stiU used in several rigid PVC appHcations in Europe and Asia. The highest use of lead stabilizers in rigid PVC is for pipe and conduit appHcations. Tribasic lead sulfate is the primary heat stabilizer with lead stearates included to provide lubrication. The lead products are typically fully formulated, usually including lubricants and pigments for pipe extmsion appHcations. These lead one-packs, when used at about 1.8—2.5 phr, provide all of the stabilizer and lubrication needed to process the polymer. A lead one-pack contains tribasic lead sulfate, dibasic lead stearate calcium stearate, polyethylene wax, paraffin wax, ester wax, and pigments. 

The most common VI improvers are methacrylate polymers and copolymers, acrylate polymers (see Acrylic ester polymers), olefin polymers and copolymers, and styrene—butadiene copolymers. The degree of VI improvement from these materials is a function of the molecular weight distribution of the polymer. VI improvers are used in engine oils, automatic transmission fluids, multipurpose tractor fluids, hydrautic fluids, and gear lubricants. Their use permits the formulation of products that provide satisfactory lubrication over a much wider temperature range than is possible using mineral oils alone. 

In order for a plasticizer to enter a polymer stmcture the polymer should be highly amorphous. Crystalline nylon retains only a small quantity of plasticizer if it retains its crystallinity. Once it has penetrated the polymer the plasticizer fills free volume and provides polymer chain lubrication, increa sing rotation and movement. 

Additives and Modifications. For plastics uses, nylon is only rarely employed as the pure polymer, and is almost always modified to some extent even if only with the addition of a small amount of lubricant. There has been a dramatic increase in the range and number of combinations of additives used to modify nylons, resulting in a huge expansion in the number of commercial grades available and the uses to which they can be put. It is not unusual to find formulations that contain less than 50% nylon and half a do2en or more additives. 

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