ELASTOMERS – Glossary of Terms

Terms Definitions
ADDITIVE A material which does not take part in the chemical reaction but is included to alter the final product eg. Fillers, pigments, flame retardants etc.
CASTING The filling of essentially open moulds with liquid polyurethane.
CATALYST An ingredient in polyurethane systems which initiates a chemical reaction or increases the rate of chemical reaction.
CHAIN REACTION Lengthening of the main chain or backbone of polymer molecules by end to end attachment.
COMPONENT A separately metered stream of liquid which will be directly introduced into the mixing head.
CROSS LINKING The formation of chemical links between the molecular chains.
CURE A term which refers to the completeness of the chemical reaction.
CURING AGENT A component that results in chemical activity between the components, with an increase in the rate of cure.
CYCLE TIME A term most commonly used in situations where many items are being manufactured on an automatic or semi-automatic production line. It includes the time required for mould preparation, including release agent application, dispensing of components, reaction, cure and demould.
DEGRADATION The deterioration of a substance caused by contact with its environment.
DEMOULD TIME The time between dispensing the liquid components into the mould and removing the article being produced.
DEW POINT The temperature at which a vapour begins to condense.
ELASTOMER A flexible or semi-rigid rubber-like material not necessarily made from what is conventionally thought of as a rubber.
ELONGATION The increase in length of a specimen at the instant before rupture occurs. Expressed as a percent of original length.
EXOTHERM Heat generated by a chemical reaction.
FLAME RETARDANT A substance which is added to a polymer formulation to reduce or retard its tendency to burn.
HARDNESS The surface property relating to the resistance of indentation.
HYDROXYL GROUP The combined oxygen and hydrogen radical (-OH) which forms the reactive group in polyols.
IMPACT RESISTANCE Ability to withstand mechanical or physical blows without the loss of protective properties.
ISOCYANATE The family name of chemical compounds having one or more NCO groups attached to the main chain.
MDI An abbreviation for diphenylMethane Di Isocyanate.
MICROCELLULAR An elastomer of cellular or foam structure.
MIL One thousandth of an inch, 0.001 inch. A unit used to measure coating thickness.
MOULDING The process of producing a finished article from a closed mould.
NDI Napthalene Di Isocyanate.
NCO Nitrogen, Carbon, Oxygen. The chemical formula for an isocyanate group.
POLYESTER Polymeric compound, with the reactive hydroxyl groups containing ester linkages.
POLYETHER Polymeric compounds with reactive hydroxyl groups containing ether linkages.
POLYMER A high molecular weight compound, natural or synthetic, whose chemical structure can be represented by a repeated small unit.
POLYOL A chemical compound with more than one reactive hydroxyl group attached to the molecule.
POST CURE The period of cure after the product has been removed from the mould. In some cases, accelerated curing at elevated temperatures is used.
POT LIFE The length of time after mixing together of the two components during which the polymer remains sufficiently liquid to be processed.
PREPOLYMER A chemical intermediate manufactured by reacting all the isocyanate with part or all of the polyol.
PTMEG Poly Tetra Methylene Ether Glycol
PU Abbreviation for Polyurethane.
RELEASE AGENT Applied to a mould to allow the foam to be demoulded easily.
RIM Reaction Injection Moulding. A process of injecting a reacting mixture of polyurethane into a mould.
SYSTEM A rather ambiguous term used to describe almost any combination of mechanical parts or chemicals which have some relationship to each other. Often used to describe the supply of all chemical components needed to produce a polyurethane.
TDI An abbreviation for Toluene Di Isocyanate.
THERMOSET A polymer that irreversibly cures from a liquid state to a solid state.
THERMOPLASTIC A polymer that turns to a liquid when heated and freezes to a solid state when cooled.
THIXOTROPIC Having the property of decreasing viscosity with increasing shear stress. A coating is thixotropic if it thins with stirring or pumping but thickens back up when movement decreases.
VISCOSITY A measure of the thickness of a liquid. The lower the number the thinner the liquid.
VOLATILE ORGANIC COMPONENTS (VOC) Organic materials which evaporate at normal temperatures and pressures, organic materials which have vapour pressure greater than 0.1 mmHg at one atmosphere.