Rubber materials are vital to modern industrial societies. And, as with any industry, rubber engineering has its own language of common terms used to define its products and processes. Though “rubber” originated from the natural milky white latex sap derived from the rubber tree, today’s rubbers are made of synthetic elastomers, a type of polymer synthesized from petroleum byproducts. The following reference guide is a short glossary of common terms often associated with rubber products and the industry in general and is intended for the use of customers and novices alike.
Guide to Rubber Engineering Terms
Acoustical Materials
Materials, generally mass-loaded vinyl (MLV), are used to reduce sound transmission, soundproof a space, or create a flexible sound barrier for specific applications.
Bond
A mechanical or chemical application that holds an elastomer to another object.
Brittleness
A form of rubber degradation where the rubber material undergoes a hardening process (embrittlement) that occurs to rubber material over time or when the material is subjected to environmental conditions incompatible with the material’s properties.
Bumper
A molded rubber component is used to absorb shock between two objects.
Compound
A combination of synthetic chemical polymers is used to create elastomeric material.
Compression Set
The amount or measure of permanent deformation that occurs to an object, such as an o-ring, affects its original density or shape after a force is removed.
Copolymer
A polymer is comprised of two different monomers.
Curing
Also referred to as vulcanization, curing is a range of processes in which the rubber’s elastomers harden in response to applying heat and sulfur. The process can give the elastomeric material its strength, elasticity, or other desired properties.
Durometer
An instrument used for measuring the indentation hardness of elastomeric and rubber materials. Higher number readings indicate a greater resistance to indentation and the hardness of materials, while lower numbers indicate less resistance and softer materials.
Dynamic Seal
A seal is applied between moving and stationary surfaces.
Elastic Deformation
The transitory dimensional change exists while initiating stress and strain on an elastic object. Once the elastic strain is removed, the object returns to its original state.
Elasticity
A material’s ability to return to its original shape after being subjected to elastic deformation.
Elastomer
A natural or synthetic polymer that holds elastic properties.
Fillers
Fillers can improve consistency, durability, and performance in rubber products. Carbon Black is the most commonly used reinforcing filler in rubber production. Silica, talc, and clay are other common fillers.
Gasket
Gaskets are mechanical seals used to create pressure-tight seams between stationary components. Once joined, gaskets prevent process fluids from escaping or contaminants from entering the component areas.
Hardness (Shore Hardness)
The measure of the resistance that a rubber material (e.g., Silicone or EPDM) has to indentation. A durometer is used to measure shore hardness.
Hermetic Seal
Any type of sealing process creates an airtight or watertight seal.
Latex
In its natural form, latex is the white, viscous, “milky” sap derived from the hevea brasiliensis variety of rubber trees. Its synthetic form is an emulsion polymer made from petroleum byproducts.
Memory (elastic)
The material property of an elastomer returns it to its original size and shape after being deformed.
Mold
A hollowed-out cavity or form cast of steel creates the desired shape when filled with a molten polymer or other pliable material. Once the liquid sets or hardens in the cavity, it adopts its shape.
O-Ring
A mechanical gasket in the shape of a torus (i.e., a doughnut), generally molded from an elastomer, is seated between two or more components in an assembly that prevents process fluids or gasses from escaping or contaminants from entering the component areas.
Oxidation
A reaction between oxygen and a rubber compound typically initiates the process of rubber degradation (such as brittleness).
Ozone Resistance
A material property of some elastomeric compounds is that they resist cracking and physical deterioration from exposure to ozone.
Permanent Deformation
The inability of an elastic object to return to its original state after being subjected to stress or strain signals the end of the object’s service life.
Permeability
The flow rate in which molecules from gas or liquid transfer through a rubber compound.
Polymer
A long molecular chain is linked together and composed of repeating subunits that form a particular material.
Rubber
The common name for an elastic substance obtained from the sap of rubber trees or an elastomeric polymer synthesized from petroleum byproducts.
Seal
A component such as a gasket or o-ring is used to prevent the passage of fluids or fine particles.
Static Seal
A gasket type application where the seal is contained within two non-moving gland walls.
Swell
An increase in seal volume is caused by exposure to, or application of, fluids, heat, lubricants, oils, and fluids, heat, and so on.
Temperature Range
The minimum and maximum service temperature in which rubber can perform effectively.
Tensile Strength
A material property that measures the maximum tension, stress, or pulling force a material can withstand while being stretched before breaking.
Thermal Expansion
The increase in the volume of a material in response to an increase in temperature.
Torque
Applying a rotational or twisting force causes an object to turn on its axis.
Torsional Strength
A material property that measures the ability of a material to withstand a twisting load and-or the maximum torsional stress that material can sustain before rupture.
Vulcanization
A chemical process in which rubber is heated with sulfur to form cross-links between long rubber molecules to improve the hardness, elasticity, and other material properties when needed, such as tensile strength and weather resistance (see Curing above).
Weathering
The tendency of rubber surfaces to undergo rubber degradation from long-term exposure to ozone, certain pollutants, and harsh environmental conditions.
