Plastics and elastomers

A variety of natural and synthetic materials are used throughout fuel and lubricant systems. Examples include transfer lines, hoses, fan blades, impellers, small gears, housings, and a host of supporting framework. Some plastics can be degraded by fuels, lubricants, additives, and various petroleum-based compounds. The most resistant material is polytetrafluoroethylene (PTFE). Ryton and Viton are less resistant, but are still quite stable in fuel and lubricant systems. Characteristics of PTFE and Ryton are shown below  

The primary considerations for the use of plastic materials in fuel and oil systems include resistance to swelling, softening, or embrittlement. Also important are flexibility and stability under a wide range of temperatures. Information on some common elastomers and plastics used in fuel systems is provided in TABLE 9-8. 

Trade Name Chemical Type Topical Properties Use 

Viton Fluoro-elastomer Resistant to degradation by fuel, temperature to 500°F (260°C) and compression Fuel line housings metering or needle valves 

Lupolen HDPE Flexible and resistant to degradation by fuel and elements of the environment Fuel tanks 

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Plastics and Elastomers. Common plastics and elastomers (qv) show exceUent resistance to hydrochloric acid within the temperature limits of the materials. Soft natural mbber compounds have been used for many years as liners for concentrated hydrochloric acid storage tanks up to a temperature of 60°C (see Rubber, natural). SemUiard mbber is used as linings in pipe and equipment at temperatures up to 70°C and hard mbber is used for pipes up to 50°C and pressures up to 345 kPa (50 psig). When contaminants are present, synthetic elastomers such as neoprene, nitrile, butyl. 

Singk-Screw E.xtruders. These iacorporate iagredients such as antioxidants (qv), stabilizers, pigments, and other fillers iato plastics and elastomers (Fig. 

Most of the phosphate esters are used in the production of hydrauHc fluids (qv), plastic and elastomer additives, flame retardants (qv), oil stabilizers, pesticides (qv), and medicinal intermediates (see Surfactants). Some trialkyl phosphates, OP(OR)2, are outstanding solvents for nitrates, especially (UO2) (N02)2, and therefore are important in uranium processing (see Extraction). 

Organophosphoms compounds, primarily phosphonic acids, are used as sequestrants, scale inhibitors, deflocculants, or ion-control agents in oil wells, cooling-tower waters, and boiler-feed waters. Organophosphates are also used as plasticizers and flame retardants in plastics and elastomers, which accounted for 22% of PCl consumed. Phosphites, in conjunction with Hquid mixed metals, such as calcium—zinc and barium—cadmium heat stabilizers, function as antioxidants and stabilizer adjutants. In 1992, such phosphoms-based chemicals amounted to slightly more than 6% of all such plastic additives and represented 8500 t of phosphoms. Because PVC production is expected to increase, the use of phosphoms additive should increase 3% aimually through 1999. 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials May attack some forms of plastics and elastomers Stability During Transport Stable Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

Tests for indention under load are performed basically like the ASTM measure the hardness of other materials, such as metals and ceramics. There are at least four popular hardness scales in use. Shore A and Shore D is for soft to relatively hard plastics and elastomers. Barcol is used from the mid-range of Shore D to above it as well as RPs. Rockwell M is used for very hard plastics (Chapter 5, MECHANICAL PROPERTY, Hardness),... 

Plastics Institute) established the materials database called Polymat. This program brings greater availability into a plastics market in which a general perspective is becoming increasingly difficult to obtain. This database contains information on plastics and elastomers, supplying about thirty to fifty properties for each material. Initially some six thousand plastics, from about seventy manufacturers, were stored. 

Permeability and Other Film Properties of Plastics and Elastomers... 

Plastomer, a nomenclature constructed from the synthesis of the words plastic and elastomer, illustrates a family of polymers, which are softer (lower hexural modulus) than the common engineering thermoplastics such as polyamides (PA), polypropylenes (PP), or polystyrenes (PS). The common, current usage of this term is reshicted by two limitahons. First, plastomers are polyolehns where the inherent crystallinity of a homopolymer of the predominant incorporated monomer (polyethylene or isotactic polypropylene [iPP]) is reduced by the incorporahon of a minority of another monomer (e.g., octene in the case of polyethylene, ethylene for iPP), which leads to amorphous segments along the polymer chain. The minor commoner is selected to distort... 

Such soft-touch materials are usually TP Vs or thermoplastic elastomers (TPEs) which combine the moldability of thermoplastics in the melt state with elasticity, lower hardness, fracture resistance, and surface characteristics of elastomers. However, plastics and elastomers respond differently to mechanical stress. Hence, both rheological behavior and mechanical strength will to a large extent depend on the morphology of the blend which may change with change in the composition. 

Figure 4. Typical poly(organophosphazene) plastics and elastomers.

Although for many decades the primary interest in the production of PHAs has been as a source of biodegradable plastics and elastomers, PHA synthesis in plants has opened novel avenues for the use of these polymers in both plant biotechnology and basic research. 

The technique of using the diffraction of X-rays to study the structure of fibres, plastics and elastomers, to determine the crystalline nature of such polymers, and to measure the particle size of finely divided materials. 

Effect of Creep and Other Time Related Factors on Plastics and Elastomers, Plastics Design Library, New York, 1991. 

Recommendations for abbreviations of terms relating to plastics and elastomers. Pure Appl. Chem. 18, 581-589 (1969). Obsolete. 

Figure 15.4 gives the stress-strain diagrams for a typical fiber, plastic, and elastomer and the average properties for each. The approximate relative area under the curve is fiber, 1 elastomers, 15 thermoplastics, 150. Coatings and adhesives, the two other types of end-uses for polymers, will vary considerably in their tensile properties, but many have moduli generally between elastomers and plastics. They must have some elongation and are usually of low crystallinity. 

Since many synthetic plastics and elastomers and some fibers are prepared by free radical polymerization, this method is important. Table 6.1 contains a listing of commercially important addition polymers including those that will be emphasized in this chapter because they are prepared using the free radical process. 

Many water-soluble vinyl monomers may be polymerized by the emulsion polymerization technique. This technique, which differs from suspension polymerization in the size of the suspended particles and in mechanism, is widely used for the production of a number of commercial plastics and elastomers. While the particles in the suspension range from 10 to 1000 nm, those in the emulsion process range from 0.05 to 5 nm in diameter. The small beads produced in the suspension process may be separated by filtering, but the latex produced in emulsion polymerization is a stable system in which the charged particles cannot be recovered by ordinary separation procedures. 

Calcium carbonate is available as ground natural limestone and as synthetic chalk. It is widely used in paints, plastics, and elastomers. The volume relationship of calcium carbonate to resin or the pigment volume required to fill voids in the resin composite is called the pigment-volume concentration (PIVC). 

FIGURE 14.6 Typical stress-strain behavior for fibers, plastics, and elastomers. 

The use of polymeric materials as basic structural materials is widespread and of ancient origin. These materials include concrete, wood, glass, and a wide variety of plastics and elastomers. In fact, with the exception of steel, most of a house is polymeric. 

Fillers are solid materials that are dispersed in plastics and elastomers. One distinguishes between inactive fillers that are used in the first place to make the plastics less expensive and active fillers (reinforcing fillers) that improve specific mechanical properties and thus effect a reinforcement . With the aid of these fillers, the elastic modulus, hardness, and thermostability are enhanced predominantly, whereas the impact strength of thermoplastic niaterials is re-... 

As a result of needs for plastics and elastomers which are more stable to high temperatures and more resistant to degrading chemical reaction than presently available polymers, a study has been made of polymer structure with units consisting of oxadicizole rings connected by per-fluoroalkyl chains 17a). 

Plastics and elastomers Degrades chlorinated polyethylene, neoprene, nitrile rubber, polysulfide, polyurethane... 

FORMULATING PLASTICS AND ELASTOMERS BY COMPUTBt by Ralph D. Hermansen... 

The early invesligations of viscoelasticity using silk, glass, and rubber may be extended to fibers, plastics, and elastomers, respectively. One of the early observations was that these materials undergo very slow irreversible flow or creep when subjected to stress over a long period of time. This irreversible effect is responsible for the so-called flat spots in nylon 66-rein-forced pneumatic tires. 

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