Compounding consists of preparing

plastic Plastics are a wide range of synthetic polymers, synthetic or Semisynthesis, semisynthetic materials composed primarily of Polymer, polymers. Their defining characteristic, Plasticity (physics), plasticity, allows them to be Injection moulding ...

formulations by mixing and/or blending

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

s and

additives Additive may refer to: Mathematics * Additive function, a function in number theory * Additive map, a function that preserves the addition operation * Additive set-function see Sigma additivity * Additive category, a preadditive category with fin ...

in a molten state to achieve the desired characteristics. These blends are automatically dosed with fixed setpoints usually through feeders/hoppers. It is mostly a blend of

copolymer In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are som ...

s such as ABS, SAN, SMA etc. with additives such as anti-oxidants, UV-stabilizers and other value adding agents and sometimes a strengthening component is added such as

glass fibre Glass fiber ( or glass fibre) is a material consisting of numerous extremely fine fibers of glass. Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the inventio ...

. There are different critical criteria to achieve a homogeneous blend of the different raw material. Dispersive and distributive mixing as well as heat are important factors. Compounding is usually done by

extrusion Extrusion is a process used to create objects of a fixed cross section (geometry), cross-sectional profile by pushing material through a Die (manufacturing), die of the desired cross-section. Its two main advantages over other manufacturing pro ...

. The hopper feeds the begin of the screw which will gradually transport the

resin A resin is a solid or highly viscous liquid that can be converted into a polymer. Resins may be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures of organic compounds, predominantly terpenes. Commo ...

s towards the die. The screw itself is confined in a barrel that has different zones that can be heated according to the resins properties. Co-kneaders and twin screws (co- and counter rotating) as well internal mixers are the most common used compounders in the

plastic industry The plastics industry manufactures polymer materials—commonly called plastics—and offers services in plastics important to a range of industries, including packaging, building and construction, electronics, aerospace, manufacturing and transpor ...

. The extrudate, which look like long plastic strands, are then cooled in a water bath, or by spraying as the conveyor belt moves it to the granulator. The granulator breaks the strands into the desired pellet sizes.

References

Plastics industry {{polymer-stub

See also

References