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.

• Medical Device Link . Bonding Elastomers with Adhesives
  From natural rubber discovered in the hevea brasiliensis plants of the Amazon Valley to thermoplastic elastomers designed in modern research laboratories, elastomers have found an important niche in...
  (read more)
• 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...
  (read more)
• Can your elastomer handle changing regulations?
  The EPA in 2000 assigned emission standards for heavy-duty highway engines built in 2007 and later. Part of the new regulations will lower the sulfur content in diesel fuel from 500 to 15 ppm. Our...
  (read more)