Thermoplastics encompass all of those plastic materials that soften and may even return to a liquid state when heated but solidify and become rigid when cooled. The majority of thermoplastics are comprised of polymeric resins. These consist of long chains of several smaller monomers held together by covalent bonds.
The popularity of these plastics may be attributed to the fact that they may be re-heated and remolded any number of times. Secondary operations, therefore, may easily redefine stock shapes and recycling is also accomplished with ease.
Thermoplastics are highly versatile and are commonly used in a number of industrial, commercial and residential settings. Medical, pharmaceutical, biomedical, food, chemical, building, electronics, construction, automotive, plumbing and virtually every modern industry make use of thermoplastics. The most used plastics, such as polyethylene, polystyrene, polycarbonate, polypropylene and PVC, are all examples of thermoplastics.
Pervasive in everyday life, these plastics are used for flooring, clothing, car interiors, airplane panels, furniture, artificial knees, pipes, insulation, plastic bags and containers, ceiling tiles and much more. Each with a different crystalline structure and density, thermoplastics offer a broad array of properties.
It is important to understand the parameters of a given plastic with regards to the final product or use. Additives, manufacturing and raw material supply are all important factors in selecting the right thermoplastic for a specific application. Further considerations include physical, mechanical, electrical and optical specifications as well as melting point, dimensions and flexibility.
Addition polymers and condensation polymers are the two main types of thermoplastics. Plastics in the addition polymers category are those which form covalent bonds without the loss of atoms or molecules in the reaction. Condensation polymers on the other hand always loose a molecule, usually water, during bonding. Within these groupings the materials can be broken down into monomers, intermediates, binders, base polymers, elastomers and rubber materials based on their chemical composition and bond formation.
Thermoplastics may be further divided by their specific properties. In addition to the polymerized materials, thermoplastic manufacturers can include additives such as powders, fibers, plasticizers, ceramics and more to improve or alter the features of a plastic material. These play a significant role in the processing and fabrication of thermoplastics.
Common manufacturing methods include injection molding, casting, extrusion, pultrusion, machining, welding and grinding. Stock shapes such as rods, sheets, films, pipes and tubes are readily available for secondary operations. Raw materials are also provided in plastic resin, liquid, powder and gel form.