Recycling Plastic

Glossary

ADDITIVE - A compound or substance added to a polymer during the final synthesis stages or in subsequent processing to improve or alter some characteristic of the polymer. Examples of additives are pigments, lubricants, flame retardants and plasticizers.

BIODEGRADABLE - Organic materials such as food scraps, paper and grass clippings that are capable of being broken down by microorganisms into simple compounds such as carbon dioxide, water or minerals.

CONTAMINANT - Any item or material that reduces the quality of material for recycling or makes it unable to be recycled.

COPOLYMER - A polymer composed of two different monomers where the repeating structural units of both are present within each molecule. The end product generally has properties intermittent between those of polymers of the two composing monomers. The two materials must have compatibility to be copolymerised.

DEGREE OF POLYMERISATION - The number of repeat units in the chain of a molecule. In a condensation polymer a repeating unit is composed of a monomer group from each reactive species.

DIELECTRIC CONSTANT - The comparison of the capacitance of an insulating material to that of air. Capacitance is the ability of a material to store electrical charge when exposed to electrical current. A low dielectric constant is desired for plastic components used to insulate and isolate electrical components from each other.

GLASS TRANSITION TEMPERATURE - The temperature at which a materials characteristics change from that of a glass to that of rubber. This temperature varies widely for thermoplastics. Some may have a glass transition temperature below zero such as polyethylene and polypropylene but still have plastic characteristics due to other factors such as crystallinity. Below their glass transition temperature these polymers become quite brittle.

GRADES - Refers to polymers which belong to the same chemical family and are produced by the same manufacturer. They may vary in processing or performance due to differences in molecular weight, additives or other structural features. For example, a polycarbonate may have flame resistant grades, glass fibre reinforced grades, a conductive grade and easy flowing grades.

MOLECULAR WEIGHT DISTRIBUTION - Statistically describes the size and frequency of occurrence of different molecular chain lengths within a given sample. Narrow distributions are more consistent.

MONOMER - Small molecules of an organic substance which are the most basic structural unit of polymers. Monomers are generally gases or liquids. When bonded together in long chains they form solid materials or polymers.

PLASTIC - A synthetic or naturally occurring organic substance generally characterised by being formable or pliable at some stage during its formation or subsequent manufacturing process.

POLYMER - A substance formed by a chemical reaction in which two or more small organic units join to form large units composed of repeating small units. The term is often used interchangeably with plastic.

POLYMERISATION - The process or chemical reaction by which low molecular weight monomers are converted to high molecular weight polymers. Most polymerisation processes are classified as condensation or step reactions or as addition or chain reactions.

RECYCLED CONTENT - The portion of a product or package that contains materials that have been recovered or otherwise diverted from the solid waste stream either during the manufacturing process or after consumer use.

RECYCLING - The process of collecting, separating and manufacturing new products from old products.

REINFORCEMENT - A substance or material added to a polymer during the final synthesis stages or in subsequent processing to improve the strength properties of the polymer.

RESIN - Any of a large class of a synthetic substances that have some of the properties of natural resin but differ chemically.

VISCOSITY - A measure of the resistance of a material when mechanical stress is applied.

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