July 10, 2013

Glossary of Plastics Terms

If you deal in plastics, as in manufacture them, sell them, use them, order them or need them in your business, there are some terms you will need to know. Over the next few blog posts, Atlantic Poly, a plastic bag and products company in MA, would like to acquaint you with some of the more necessary plastics terms.

Additive: A compound or substance added to a polymer to improve or alter some characteristic of the polymer. Examples include pigments, antistats and flame retardant.

Antiblock Agent: Additive incorporated in film to prevent the adhesion (sticking) between touching layers of film during fabrication, storage, or use.

Antioxidant: An additive which inhibits the degradation and oxidation of material when exposed to ambient air during processing and subsequently in the end product form.

Antistatic Agent: Additive which imparts a slight degree of electrical conductivity to plastics, permitting the dissipation of static electricity.

Average Molecular Weight: Molecular weight of polymers is determined by viscosity of the material in solution at a specific temperature. This results in an average molecular weight of the molecular chains independent of specific chain length. The value obtained falls between weight and number average molecular weight.

Banbury Mixer: A compounding apparatus consisting of two contra-rotating spiral-shaped blades encased in intersecting cylindrical housings so as to leave a ridge between blades.

Barrel: The tubular portion of the extruder or injection molding machine in which the extruder screw is placed and rotates.

Barrier Resins: Polymers which have very low permeability to gases.

Beta Gauge: A thickness measuring device used for sheeting or extruded pans. The device operates by beta radiation being emitted on one side of the pan and a detector placed on the opposite side. When a pan is passed through the beam, some of the beta radiation is absorbed, which is indicative of the pan thickness.

Biaxial Orientation: The process of stretching a hot plastic film or other article in two directions under conditions resulting in molecular orientation in two directions.

Biodegradation: The degradation of plastics by microorganisms when buried in the soil. Some plastics can be modified to become biodegradable by the incorporation of a biodegradable additive such as corn starch.

Blend: The mixing of polymers with other polymers or copolymers, usually where the mixture results in the desired physical properties.

Blocking: An undesirable adhesion between layers of film or sheeting which may have developed during processing or storage. Blocking can be prevented by adding antiblock agents to the resin.

Bloom: A thin, greasy film on the surface of a plastic film or pan usually caused by the exudation of an additive. Slip additives are designed to migrate or bloom to the surface of films.

Breaker Plate: A perforated plate located at the rear end of an extruder head or die adapter serving to support the screen pack. The breaker plat also helps to generate back pressure in extrusion.

Bulk Density: The density (mass per unit of volume) of a resin in solid form (granular, nodular, pellet, powder, etc.) expressed in g/cm3 or lb/ft3.

For information on anything plastic, contact Atlantic Poly.