Glossary Of Terms


A carbon chain of varying length with a double bond in between the first and second carbon atom.


A chemical substance which inhibits oxidation or degradation of a polymer material such as polypropylene in which it is incorporated. Antioxidants capture polymer chain-breaking free radicals or convert peroxides into stable materials.

Block Copolymer

A polymer composed of repeated sequences based on different monomers such as propylene and ethylene.

Blowing Agent

A process additive (also known as foaming agent) that will form a gas during injection molding which results in a porous product containing tiny cells or bubbles. They are intended to reduce the density or mass of an application, create certain structural characteristics, or eliminate sink marks.

Blow Molding

A production process for thermoplastics where a hollow tube of molten plastic is forced into the shape of the mold cavity by exerting internal air pressure.

Calcium Carbonate

A common mineral filler or reinforcement. Calcium Carbonate can be surface-modified to improve heat stability and lubricity during extrusion. While modified grades of calcium carbonate promote impact strength and smooth surfaces, unmodified grades can provide cost efficient dimensional stability.

Carbon Black

A pigment commonly used in polyolefins that increases the resistance to UV radiation. Certain grades can increase electrical conductivity in thermoplastics.

Chopped Glass Fiber

A term that describes various lengths of bundled filaments of glass fibers. This material is used in RheTech compounds as a reinforcement to increase tensile, flexural, and thermal properties.

Coefficient of Linear Thermal Expansion (CLTE)

The dimensional change of a material with respect to change in temperature.

Compound (polymer)

A material typically composed of one or more thermoplastics combined with various reinforcements, fillers, modifiers, pigments, additives, and stabilizers to enhance performance characteristics of the original base polymer.

Copolymer (Polypropylene)

Typically a higher impact grade of polypropylene that is manufactured from propylene and ethylene monomers. See also Block Copolymer.

Coupling Agent

An additive used to improve adhesion between glass fibers and the polymer matrix. It chemically attaches to the glass fiber surface and creates a more resin-compatible surface.


A thermoplastic property defined by mass per unit of volume at a specified temperature.


The ability of a material to return to its original shape when load causing deformation is removed.


The measurement of the ductility of a thermoplastic determined by a tension test. It is the increase in gauge length (measured after rupture) divided by the original gauge length.


A manufacturing process used in the production of RheTech materials. Polyolefins are compounded with various reinforcements, fillers, modifiers, pigments, additives, and stabilizers in a molten state then cooled and cut into uniform pellets. It is also a melt process for producing plastic profiles.

Flame Retardant

A chemical additive used in certain RheTech compounds to reduce the flammability of a given material by either suppressing, preventing or extinguishing flame spread. Flame retardant function varies depending on the nature of the retardant and the material into which it is incorporated.

Flexural Modulus of Elasticity

The ratio of stress to corresponding strain on a material specimen in a 3-point bending test, the rate of change of strain as a function of stress.

Flexural Strain

The percentage of deformation of a material specimen at midpoint in a 3-point bending test.

Flexural Strength

The maximum fiber stress developed in a specimen as a function of strain in a 3-point bending test.

Flexural Stress

The maximum fiber stress in a specimen at any given strain in a 3-point bending test. It is a function of load, support span, and specimen geometry.

Fractional Melt Index Resin

A thermoplastic having a melt index of less than 1 g/10 min. This is an indication of a higher molecular weight polymer. It is typically used in film, blow molding and profile extrusion processes.

Gardner Impact

A drop dart test used to determine impact performance of plastics.

Heat Deflection Temperature

The temperature at which a material specimen deflects by a certain degree under a specified load.


A polymer that contains only a single type of monomer (i.e. propylene or ethylene).

Injection Molding

A part fabrication process where molten thermoplastics are injected into a mold cavity.

Izod Impact Energy

A measure of impact performance for plastics (i.e. polypropylene) determined by a pendulum impact on a specimen.

Melt Flow Rate

A measure of molten resin viscosity determined by an extrusion rheometer. It is typically performed at 230°C and 2130 grams of weight for polypropylene. Units are reported in g/10 min.

Melt Index

(see Melt Flow Rate) is a similar test as melt flow rate but typically performed at 190°C and 2130 grams for polyethylene.


A crystalline, platy reinforcing filler for thermoplastics resulting in improved stiffness, thermal properties, and good dimensional stability. Grades vary according to ore source, grinding method, and particle size. These attributes determine property performance improvements in polypropylene.

Mineral Reinforcements

A large family of inorganic materials comprised of natural or refined minerals. They are typically ground into small particle sizes and used to enhance physical properties in thermoplastics. Examples include calcium carbonate, mica, talc and wollastonite.

Modulus of Elasticity

The ratio of stress to corresponding strain on a material specimen in a tension test. This is also known as tensile modulus or Young’s Modulus.

Mold Shrinkage

Mold Shrinkage is the percentage of reduction in size of a molded specimen or part in reference to the dimension(s) of the mold cavity. Note: this is a time-dependent value.


An individual molecule that is the building block of polymers such as polyethylene or polypropylene.


A chemical substance composed of many repeat units of a monomer. Polymers can have molecular chains that are either linear, cross-linked or branched. Synthetic polymers are created by polymerization of one or more monomers.


A large family of carbon-chain elastomeric and thermoplastic polymers. They are generally manufactured through the polymerization of olefins or alkenes such as propylene or ethylene.

Specific Gravity

A ratio of a material’s density in relation to the density of water at 23°C.


A chemical that is incorporated into polymers that inhibits certain chemical degradation reactions in the resin compound. Stabilizers can minimize molecular weight reduction caused from melt processing, heat exposure, and UV radiation.


A platy reinforcing filler that improves stiffness, dimensional stability and thermal properties. Talc can be ground into various particle sizes which determine the physical properties in talc reinforced polypropylenes which are easy to color.

Tensile Modulus

(see Modulus of Elasticity)

Tensile Strain

The relative length of deformation observed in a sample specimen having been subjected to tension force (see Elongation).

Tensile Strength

The maximum applied force divided by the original cross-sectional area of a specimen subjected to a tension test.

Tensile Stress

The applied force divided by the original cross-sectional area of a specimen subjected to a tension test at any given strain.


Melt-processable polymers which can be repeatedly melted, formed and reprocessed. There are a multitude of classes depending on the monomer types.

Thermoplastic Polyolefin (TPO, TEO)

Typically an impact modified polypropylene that may also contain a reinforcing filler such as talc. Impact modifiers are usually alpha-olefin ethylene copolymers that are used to increase impact and flexibility.


A fibrous mineral reinforcing filler which increases flexural properties and dimensional stability.

Young’s Modulus

(see Modulus of Elasticity)