Elastomers and Rubber Materials

Elastomers and rubber materials are characterized by their high degree of flexibility and elasticity. They are based on a variety of chemical systems. Examples include acrylics and polyacrylates; butyl, polybutene and polyisobutylene polymers; ethylene copolymers; fluropolymers such as polytetrafluorethylene (PTFE); silicone, polyurethane, and polyether block amide (PEBA); styrene butadiene rubber (SBR); and vinyl and polyvinyl chloride (PVC). Elastomers and rubber materials often contain filler materials such as powders or fibers to provide improved strength and/or stiffness. Fibers can be either chopped or wound, and commonly include glass, fiberglass, or cloth. Some elastomers and rubber materials contain solid lubricant fillers such as graphite or molybdenum disulfide. Others contain aramid fibers, metal powders, or inorganic fillers with ceramics and silicates.   

Many types of elastomers and rubber materials are available. Thermoset plastics and thermoset resins are crosslinked polymers that are cured with heat or heat and pressure. Thermoplastics can be softened repeatedly by heat and then hardened or set by cooling. Filled or reinforced products consist of resins and additional modifiers such as pigments, plasticizers, or chopped fibers. By contrast, unfilled resins, base polymers, and raw materials do not contain additives. Typically, raw materials are available as pellets, powders, granules, or liquids. Stock shapes such as bars, sheets, and film are also available. Molding compounds are designed for processes such as reaction injection molding (RIM) and resin transfer molding (RTM). Composite materials consist of a matrix and a dispersed, fibrous or continuous second phase. Casting resins include a catalyst or hardener. Electrical resins and electronic-grade polymers and elastomers are used in potting or encapsulating compounds, conductive adhesives, and dielectric sealants. Specialized elastomers and rubber materials are used in optical and photonics applications and in mold and tooling fabrication. Monomers and intermediates are commonly available.

Important specifications for elastomers and rubber materials include mechanical, thermal, electrical, optical, processing, and physical properties. Mechanical properties include flexural strength or yield, tear strength, ultimate tensile strength (UTS), yield strength (YS), tensile modulus or modulus of elasticity, elongation, and impact toughness as measured with an Izod test and a notched sample. Thermal properties include maximum use temperature, deflection temperature at 264 psi or 1.8 MPa, glass transition temperature, thermal conductivity, and coefficient of thermal expansion (CTE). Electrical and optical properties include electrical resistivity, dielectric strength, dielectric constant or relative permittivity, index of refraction, and light transmission. Processing and physical properties include bulk or apparent density, water absorption, viscosity, process temperature, and melt flow index (MFI).

Elastomers and rubber materials provide a variety of features. For example, products that are designed for electrical and electronics applications often provide protection against electrostatic discharge (ESD), electromagnetic interference (EMI), or radio frequency interference (RFI). Materials that are electrically conductive, resistive, insulating, or suitable for high voltage applications are commonly available. Flame retardant materials reduce the spread of flames or resist ignition when exposed to high temperatures. Thermal compounds form a thermally conductive layer on a substrate, either between components or within a finished electronic product. Thermal interface materials with a phase change increase the heat absorption from semiconductors, electronic devices, or electrical components.

• The Rapra Collection of Infrared Spectra of Rubbers, Plastics and Thermoplastic Elastomers, Third Edition
  The Rapra Collection of Infrared Spectra of Rubbers, Plastics and Thermoplastic Elastomers, Third Edition Including copolymers and blends, which are in current use, this book provides a set of...
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• Biofuels: a Challenge to Fuel Seal Elastomers?
  Biofuels - bioethanol, biobutanol and biodiesel - are becoming a significant reality in the transportation fuels landscape in the USA and North America, as well as Europe, South America and the...
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• Protective Materials for Maritime Vessels (.pdf)
  As early as 1950 a new generation of composite materials was being developed to support the offshore oil & gas, aerospace, and defense industries. These materials included syntactic foams, glass and...
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