by International Polymer Engineering
Plastics that are both strong and lightweight improve the safety, performance and convenience of a wide variety of products that we all use every single day. Plastics consist mainly of macromolecules that are processed into molded parts, films, fibers or finished/semi-finished products. The specific characteristics of just about any plastic materials can be further adjusted with special additives and coatings.
When selecting a plastic for your application you will want to look closely at its technical properties, things such as:
- Hardness
- Breaking strength
- Formability
- Elasticity
- Temperature restrictions
- Chemical resistance
- And more
Plastics are classified into three categories according to their physical properties:
- Thermoplastics
- Thermosets
- Elastomers
Thermoplastic
Thermoplastic material (or thermosoftening plastic) is a type of plastic polymer material (or plastomer) that becomes pliable at elevated temperatures and becomes less so once it has cooled. The name comes from thermo which means warm or hot, and “plast” which comes from the ancient Greek word ‘plássein’ which means to form or mold. Thermoplastic materials can withstand very high temperatures so the heat required for melt processing must be even higher. Unlike thermosets, thermoplastic materials can be molded as often as is desired by cooling and reheating them, as long as the material is not overheated. Overheating causes the material to decompose. Another interesting property of thermoplastics that is unique to this category is that some thermoplastics can actually be welded.
Thermosets
Thermosets are plastics that retain their condition and shape after curing due to spatial crosslinking. Once cured, their polymers can no longer be dissolved. This type of plastic is popular in electrical installations due to its mechanical and chemical resistance, even at high temperatures. Popular thermosets include phenoplastics, virtually all synthetic resins (such as epoxy resins), polyurethane resins for paints and surface coatings and polyester.
What is the difference between thermoplastics and thermosets in the manufacturing process?
Elastomers
Elastomers (or “elastic polymers”) are polymers that are held together by weak intermolecular forces, generally exhibiting low Young’s modulus and high yield strength or high failure strain. They are also viscous as well as elastic, a property known as viscoelasticity. These plastics have unique properties that allow them to deform or stretch under extreme tensile and compressive loads then return to their original shape. Examples of elastomers include natural rubber, polyurethanes, polybutadieve, silicone and neoprene. This type of plastic is popular as a material for tires, rubber bands, baby pacifiers, belts, prosthetics and other items of this nature.
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