Health & Safety
Chemical Name: Rubber or Elastomer
Chemical Family: Hydrocarbons or Silicones
Formula: Rubber with Inorganic and Organic Fillers
Melting/Boiling Point: None (thermoset material)
Density: 1.0 to 2.0
Appearance: Black or coloured solid elastomer
These guidelines are intended to draw the attention of designers and users of rubber parts to some of the material’s specific properties and behaviour. They should be read in conjunction with the national and international standards and legislation relating to the properties and safe application of rubber.
Parts made of rubber may deteriorate in storage, therefore before assembly or when not in use they should be stored in a cool, dark environment with minimum air changes. Rubber parts should not be contaminated by oils or other harmful substances, nor be subjected to excessive forces which may permanently deform them.
Some rubbers partially crystallise at room or lower temperatures. This will change their hardness and flexibility. Neoprene in particular crystallises significantly unless special resistant grades are used.
Crystallisation can generally be removed by heating to 100°C for 30 minutes.
All elastomers become stiffer and less rubbery at low temperatures. This may impair their function, for example, a seal may not work if the rubber becomes less flexible. Generally properties are completely regained as the temperature rises.
Designers must ensure that their products are safe if low temperature storage or operation is possible. Special formulations are available to suit these conditions.
Rubbers deteriorate as their temperature is raised. Each compound has a maximum safe continuous working temperature which depends upon the formulation, service conditions and level of properties required. This temperature may sometimes be exceeded for short periods if some deterioration of the properties can be safely allowed.
Rapid bending or stretching of rubber parts may also lead to a damaging build-up of heat (hysteresis) within the part - for example, a flat tyre.
Rubber which has been overheated will have severely reduced properties and parts may be unable to function as designed. It can also produce unpleasant or dangerous substances, depending upon the base rubber and additives used in the compound.
The typical temperatures for continuous and intermittent duty listed in “Engineering in Rubber” are based on simple laboratory air ageing tests. The only way to ensure totally satisfactory operation is to test the actual rubber compounds under normal (and abnormal) conditions of use.
Most rubbers are based on hydrocarbons and will burn. Self-extinguishing properties can be obtained by appropriate compounding.
Burning rubber produces great heat and acrid smoke which may contain harmful constituents, including halogens. Fire fighters should be specifically trained to deal with the hazard.
Finely divided rubber, such as that produced by grinding or buffing, should be removed safely from the working area. Rubber dust is readily ignited and can burn fiercely or explode. Spontaneous combustion can occur and rubber crumb or dust should be kept in small quantities until cool.
Dust extraction systems should also be regularly cleaned to avoid the risk of fire.
Many rubbers exhibit surface cracking and other forms of deterioration in use, especially in the presence of ozone. Cracking or hardening of the surface of a rubber component may render it likely to fail. Users must inspect rubber parts for signs of deterioration at suitable intervals for the needs of the application. Any parts showing such signs should be replaced immediately.
Properties can also be affected by oils, fluids and gases which may cause volume changes.
Resistance to Chemicals, Oils & Fluids
No rubber resists all chemicals. Compounds must be selected to perform in specific environments and may be affected or damaged by exposure to chemicals, oils or fluids. Designers should therefore specify all likely and possible contaminants and carry out tests to ensure that the finished parts function safely.
Bonded Rubber Parts
The exposure of bonded parts to harmful substances and high or low temperatures may cause failure. Components should be inspected for bond integrity as often as required by the application. Metal parts should be checked for corrosion which may destroy the bond.
Friction properties will vary widely depending upon the surfaces involved and the presence of oils, water and other substances.
Rubbers can be manufactured to be highly insulative or conductive. Designers and users should be aware of these properties and ensure that appropriate materials are specified and tested in use.
It must not be assumed that black rubber compounds have insulating properties, since conductive carbon black is a common reinforcing ingredient.
When exposed to ionising radiation, rubbers will undergo increased cross-linking and become harder and less elastic.
Fire & Explosion Hazard
Explosive Hazard: Rubber dust is readily ignited and can burn fiercely or explode. Spontaneous combustion can occur, so rubber crumb should be kept in small quantities until cool. Dust extraction systems should be regularly cleaned to avoid the risk of fire.
Fire Fighting Procedure: Rubber burns exothermically and produces fumes, some of which are toxic. The area should be evacuated. Respiratory protection should be worn when fire fighting.
Extinguishing Media: Usual standard types.
Health Hazard Data
Result of Exposure: None
Ingestion: Consult a Doctor. Only specially formulated rubber is suitable for oral or food contact. Materials intended for such use require special clearance.
Skin: Possible allergic reaction
Inhalation: Inhalation of rubber dust or fumes should be avoided.
The Harboro Rubber Company Limited manufactures parts to the specifications and drawings supplied by clients. It is a Condition of Sale that customers assure themselves that the parts supplied are safe in use and have been tested under actual conditions of use. It is the direct responsibility of the customer to make the final user or users aware of the conditions for safe use of any product incorporating parts made from rubber.