Two-component polyurea elastomeric coating/lining systems are the newest technology in the protective coating/lining industry and a wide variety of applications have been developed. These include coating/lining applications over concrete, geotextile membranes, various metals for corrosion and decorative areas, and some plastics. This article discusses the formulation basics of polyurea technology and compares the technology to that of polyurethane and polyurethane/polyurea systems. It addresses performance issues and describes application processing considerations and safety practices of polyurea coating/lining systems.

Phosphoric acid is less corrosive than sulfuric and hydrochloric acids. This article discusses the corrosion rates of metal alloys in phosphoric acid, including aluminum, carbon steel and cast irons, stainless steels, nickel-rich G-type alloys, copper and copper alloys, nickel alloys, lead, titanium alloys, and zirconium alloys. Nonmetallic materials may be chemically attacked in some corrosive environments, which can result in swelling, hardening, or softening phenomena; extraction of ingredients; chemical conversion of the nonmetallic constituents; cross-linking oxidation; and/or substitution reactions. The article also describes the corrosion resistance of nonmetallic materials such as rubber and elastomeric materials, plastics, carbon and graphite, and ceramic materials.

Hydrochloric acid (HCl) may contain traces of impurities that will change the aggressiveness of the solution. This article discusses the effects of impurities such as fluorides, ferric salts, cupric salts, chlorine, and organic solvents, in HCl. It describes the corrosion resistance of various metals and alloys in HCl, including carbon and alloy steels, austenitic stainless steels, standard ferritic stainless steels, nickel and nickel alloys, copper and copper alloys, corrosion-resistant cast iron, zirconium, titanium and titanium alloys, tantalum and its alloys, and noble metals. The article illustrates the effect of HCl on nonmetallic materials such as natural rubber, neoprene, thermoplastics, and reinforced thermoset plastics. It also tabulates the corrosion of various metals in dry hydrogen chloride.

Natural and synthetic rubber linings are used extensively in many industries for their corrosion and/or abrasion resistance. These industries include transportation, chemical processing, water treatment, power, mineral processing, and mining. This article provides information on soft natural rubber, semihard natural rubber, hard natural rubber, neoprene or polychloroprene, chlorobutyl, three-ply linings, nitrile, and ethylene propylene with a diene monomer. Emphasis is placed on advantages, disadvantages, and common uses of each material discussed.

Elastomers belong to a group of materials known as polymers that acquire their properties and strength from their molecular weight, chain entanglements, and crystalline regions. This article focuses on the use of elastomers as seals and describes its performance capabilities from the point of a sealant. The important technical concepts that define the performance capabilities of the elastomeric part include polymer architecture (molecular building blocks), compounding (the ingredients within the polymer), and vulcanization of the elastomer shape. The article discusses the aggressiveness of the chemical environment, temperature, and minor constituents in the environment and in the material itself that affect the chemical resistance of the elastomer. It provides a discussion on performance evaluation methods, namely, immersion testing and application specific testing that are determined using ISO and ASTM standards. The article concludes with information on elastomer failure modes and failure analysis.

This article provides an overview of the environmental performance of the most commonly used nonmetallic materials, including elastomers, plastics, thermosetting resins, resin-matrix composites, organic coatings, concrete, refractories, and ceramics. It also discusses the applications and uses of these materials.

Plastics or polymers are used in a variety of engineering and nonengineering applications where they are subjected to surface damage and wear. This article discusses the classification of polymer wear mechanisms based on the methodologies of defining the types of wear. The first classification is based on the two-term model that divides wear mechanisms into interfacial and bulk or cohesive. The second is based on the perceived wear mechanism. The third classification is specific to polymers and draws the distinction based on mechanical properties of polymers. In this classification, wear study is separated as elastomers, thermosets, glassy thermoplastics, and semicrystalline thermoplastics. The article describes the effects of environment and lubricant on the wear failures of polymers. It presents a case study on nylon as a tribological material. The article explains the wear failure of an antifriction bearing, a nylon driving gear, and a polyoxymethylene gear wheel.

Elastomeric tooling uses rubber details to generate required molding pressure or to serve as a pressure intensifier during composite part curing cycles. This article discusses the various aspects of the forms of commercially available bag-side elastomeric caul systems. It describes the two basic methods, such as the trapped or fixed-volume rubber method and the variable-volume rubber method, of elastomeric tooling, which use the principles of thermal expansion molding. The significant properties and controlling equations that are required to characterize elastomeric tooling material are also discussed.

This article reviews the general mechanical properties and test methods commonly used for ceramics and three categories of polymers, namely, fibers, plastics, and elastomers. The mechanical test methods for determining the tensile strength, yield strength, yield point, and elongation of plastics include the short-term tensile test, the compressive strength test, the flexural strength test, and the heat deflection temperature test. The most commonly used tests for impact performance of plastics are the Izod notched-beam test, the Charpy notched-beam test, and the dart penetration test. Two basic test methods for a group or strand of fibers are the single-filament tension and tow tensile tests. Room temperature strength tests, high-temperature strength tests, and proof tests are used for testing the properties of ceramics.

This article is a comprehensive collection of tables that list the values for hardness of plastics, rubber, elastomers, and metals. The tables also list the tensile yield strength and tensile modulus of metals and plastics at room temperature. A comparison of various engineering materials, on the basis of tensile strength, is also provided.

This article is a comprehensive collection of engineering tables providing information on the mechanical properties of and the techniques for processing and characterizing polymeric materials, such as thermosets, thermoset-matrix unidirectional advanced composites, and unreinforced and carbon-and glass-reinforced engineering thermoplastics. Values are also provided for chemical resistance ratings for selected plastics and metals, and hardness of selected elastomers.

In terms of their electrical properties, plastics can be divided into thermosetting and thermoplastic materials, some of which are conductive or semiconductive. This article provides detailed information on factors that affect the property of plastics. It discusses the major test methods used to determine the following dielectric properties of plastics: dielectric breakdown voltage, dielectric strength, dielectric constant, dissipation factor, arc tracking resistance, insulation resistance, volume, and surface resistivity or conductivity. The test specifications and conditions, recommended by several U.S. and foreign testing organizations for characterizing the electrical properties of plastic materials are listed. The article describes the influence of these properties on selection of plastics for insulation application. An outline of the electromagnetic shielding and testing methods of electromagnetic interference are also provided. Designations, electrical properties, and applications of elastomers are tabulated.

Tribology is the science and technology of interacting surfaces in relative motion or, the study of friction, wear, and lubrication. This article focuses on friction and wear processes that aid in the evaluation and selection of materials, for polymers and some composites used in friction and wear applications. It provides information on friction, types of wear, and lubrication. The article includes a brief description of the friction and wear test methods, laboratory-scale friction, and wear testing, usually performed either to rank the performance of candidate materials for an application or to investigate a particular wear process. It describes the wear tests conducted with/without abrasives and explains the concept of PV limit (where P is contact pressure and V is velocity). The article concludes with references and tables of friction and wear test data for polymeric materials.

This article discusses the properties, chemical structures, and applications of different types of elastomers grouped based on their resistance to aging (oxidative degradation), solvents, and temperature. These include butadiene rubber, natural rubber, isoprene rubber, chloroprene rubber, styrene-butadiene rubber, aerylonitrile-butadiene (nitrile) rubber, isobutylene-isoprene (butyl) rubber, ethylene-propylene (-diene) rubber, and silicone rubber. The article also provides an outline of the concerns related to the processing stages of rubbers or elastomers, including mixing or compounding, shaping, and vulcanizing or crosslinking.

Additives for plastics and elastomers are used to increase the ease of processing and to improve the properties of the final product. Additives improve processing characteristics by increasing lubricity and by stabilizing the polymer. Additives that improve properties include those that decrease static charge development and microbial activity and those that improve flame retardation characteristics, color, light stability, impact resistance, density and mechanical properties. This article focuses on the additives for polymers and elastomers that are used for improving processing--blowing agents, mold-release agents, lubricants, plasticizers, and heat stabilizers--and for improving properties antimicrobials, antioxidants, antistatic agents, colorants, fillers and fiber reinforcements, flame retardants, impact modifiers, light stabilizers, plasticizers, and heat stabilizers. Furthermore, it discusses the method for addition of these additives and the problems faced during compounding.