How to Select Polymers and Plastic Materials

Polymers and plastic materials are high molecular weight compounds comprised of two or more repeating organic or synthetic base molecules.

Types of Polymers and Plastic Materials

The GlobalSpec SpecSearch Database contains these types of polymer and plastic materials.

• Thermoplastics are polymers that turn to liquid when heated and turn solid when cooled. They can be repeatedly remelted and remolded, allowing parts and scraps to be reprocessed. In most cases they are also very recyclable.
• Elastomers and rubber materials are characterized by their high degree of flexibility and elasticity (high reversible elongation). They are based on a variety of different systems, including silicone, polyurethane, chloroprene, butyl, polybutadiene, neoprene, natural rubber or isoprene, and other synthetic rubber or compounds.
• Thermosets or thermosetting plastics are polymer materials that have been irreversibly cured. They are generally stronger than thermoplastics due to polymer cross-linking and are better suited for high-temperature applications (below their decomposition points). They tend to be more brittle than thermoplastics and many cannot be recycled due to irreversibility.

Polymer and Plastic Material Properties

Special consideration should be given to properties such use temperature, coefficient of thermal expansion, thermal conductivity, and tensile strength. Use temperature is the allowable temperature range in which the compound can operate effectively which determines what environments the resin can be used in. The coefficient of thermal expansion is a measure of the tendency of the compound to change in volume in response to temperature, which could limit space restraints under certain operating temperatures.

The thermal conductivity of the polymer is a measure of how well the material conducts heat or transfers heat, which is important for temperature conscious environments. Tensile strength is the maximum stress a material can withstand while being stretched or pulled before necking deformation occurs.

Material Types and Grades

Material types for polymers and plastic materials include cross-linked materials and resins, and compounded raw materials such as pellets and liquids. Electrical and electronic materials, optical grade materials, and self-lubricated or bearing-grade plastics and plastic materials are also available.

Cure Type and Components

Cure type or cure technology is also an important consideration when selecting products. Choices include air setting or film drying, anaerobic, thermoplastic or hot melt, thermosetting or cross-linking, room-temperature curing or vulcanizing, and pressure sensitive adhesive (PSA). Polymers and plastic materials that are cured with ultraviolet light (UV) are also available, as are reactive resins, single-component products, and two-component systems.