Manufacturers use thermoplastics because they're easy to mold and shape when they're hot. Some types of thermoplastics are expensive, strong and used in place of metal, while others are used in common everyday products. Thermoplastics are materials that turn to liquid at high temperatures, but when they cool turn into hard, solid plastic. Keyboards are often made of thermoplastics. Another common use of thermoplastics is for compact disc cases.
Thermoplastics are well suited for many different types of uses, because they have high strength, are lightweight and have relatively low processing costs. In addition, it's relatively easy to manufacture thermoplastic components quickly in high volumes with high precision. Sometimes engineers use thermoplastics instead of metals because of their much lighter weight.
The primary disadvantage of using thermoplastics instead of materials like metal is that thermoplastics can melt. Some types of low-quality thermoplastics melt when they're exposed to ultraviolet light for extended times. In addition, thermoplastics can have poor resistance to organic solvents, hydrocarbons and highly polar solvents. Thermoplastics are sometimes the victim of creep, which is when the material relaxes or weakens when exposed to long-term loading. Some types of thermoplastics, such as composites, fracture instead of becoming deformed when exposed to high levels of stress.
The two types of thermoplastics are high-temperature thermoplastics and engineering thermoplastics. Examples of high-temperature thermoplastics include common materials such as polypropylene and PVC. Engineering thermoplastics cost much more to produce than these common materials, and include materials such as nylons and polyesters. Thermoplastics can be as soft as rubber or as strong as aluminum, depending on how they're made. Some types of high-temperature thermoplastics are capable of withstanding temperature of up to 600 degrees F. without melting. Other types of thermoplastics can maintain their original properties in temperatures as cold as -100 degrees F. The majority of thermoplastics are excellent thermal and electric insulators. Engineering thermoplastics are typically flame-retardant and can withstand temperatures of up to 100 degrees C.
One type of thermoplastic, called polyvinyl chloride, or PVC, is commonly used for pipes, bottles and plastic containers. Another type, called polyester resin, is used for car bodies and garden furniture. A third type, polymethyl methacrylate, is used for things such as lenses and windows.