Plastic rods are sometimes filled with metal and used in industrial equipment and construction as structural support; in applications requiring little structural strength, plastic rods may be co-extruded with lower cost material on the inside, cutting down on the cost for both the manufacturer and the customer.
Many manufacturers of equipment for aerospace, transportation, electronics, marine and petrochemical use solid plastic rods as raw materials to be machined into parts for bearings, corrosion-resistant pieces, gaskets, seals, insulation, sleeving and static control.
Plastic sheets and blocks are also used to make parts in many of the same industries, although the types of parts can be different; rather than a support part for a building or machine, plastic sheets would be utilized for machine guards or windows.
Both plastic sheets and plastic rods are ideal materials for these industries due to the unique properties of plastic, such as low density, structural integrity, non-conduction, low porosity and properties of heat and corrosion resistance. Plastic is not only light and easily shaped, but the different types of chemical combinations offer a broad selection of desired properties.
There are many varieties of plastic formulas, although most of them fall into one of two categories; thermoplastics and thermosets.
Thermoplastics include all plastics that melt when heated to a certain degree, but harden when they cool.
Thermosets also melt when heated and harden when cooled, although they can not be reheated, reshaped and rehardened as thermoplastic can, which gives the many types of thermoplastics the advantage.
Positive and negative characteristics make each plastic particularly attractive for certain industries more then others. Acetal plastic rods, for example, are chemically-resistant and have very low water absorption, making them popular for food processing applications. However, acetal has relatively low strength and resistance to high heat, and applications that require high strength and heat resistance use PVC or noryl.
PVC is commonly used in sewage treatment, building exteriors, metal anodizing and chemical processing because of its high heat, fire and chemical resistance. Other types of plastic, such as acrylic and HDPE, are valued for their flexibility, scratch-resistance and their ability to be easily machined.