Plastic compounding is a process for adding additional materials into a molten plastic base to produce a material with desired qualities. Additives and modifiers may result in plastic with a particular color, texture, strength, and so on. A manufacturer may incorporate one or more additives into the base material in the process of plastic compounding.

While the process is different in each facility depending on the product being produced, plastic compounding typically involves several basic steps. Additives in the form of pellets, flakes, or powders are conveyed to a container of a molten plastic base material. The mixture goes through a number of blending and dispersal steps to incorporate these additives into the base material and achieve a homogeneous final product. Processing may also include steps to reduce the chemical volatility of the material. Once all processing steps are complete, the material is cooled and extruded into pellets, which are then packaged for distribution or sale.

Polyethylene and polypropylene are the two most common base polymers used in the plastic compounding process. Modifiers may be added to these base polymers in the form of powder or small pellets. Sometimes recycled material is added in the form of chips or shavings produced in the recycling process.

Filler material may be classified as either inert or active. Inert filler material typically increases the volume of the material inexpensively without adding any beneficial features. Its primary purpose is to reduce the cost of the material. Active filler, on the other hand, is added to improve the physical properties of the material. If a filler increases the tensile strength of the base material, it may be referred to as a reinforcement.

Manufacturers must take into account a number of factors when incorporating additives. Physical properties such as particle size and shape of the additive must be compatible with the base material. Even if it improves performance, an expensive additive may drive the price of the final product up too much for its target market. Suitability of an additive in the manufacturing environment must also be considered. For example, abrasive filler materials can degrade plastic compounding equipment, and dust from an additive in powder form may contaminate the manufacturing facility.

Modifiers used in plastic compounding serve a number of purposes when added to base polymers. They may reduce the cost of the final material substantially, thereby providing an economic advantage in the marketplace. Use of recycled material as additives can reduce consumer or industrial waste in landfills and save on waste disposal expenses.

Additionally, additives may improve the quality of the final product in a number of ways. Flame retardants and antioxidants may improve the safety of the material or extend its useful lifetime. Antacids may be added to a material to reduce the impact it has on the equipment used for processing. Glass or carbon fibers can increase the strength of a base polymer when incorporated into it.

A wide variety of products are made with materials developed through plastic compounding. Consumer products that incorporate these materials include toys, furniture, appliances, and more. Industrial applications include use in automotive components, pipes, construction, and others. The diverse array of materials that can be created with plastic compounding ensure widespread use of this process in product manufacturing well into the future.