Guidelines and recommendations for the storage of polyurethan and elastomer seals

During storage, the characteristics of the elastomers and of the products in plastic or polyurethane can be damaged by:

• chemical reactions which are fundamentally caused by the influence of heat, light, oxygen, ozone, humidity and various chemical agents
• physical process

This physical process called “physical ageing”, is caused by the influence of external tensions, leading to cracks and permanent deformation, or by the migration of plasticizers from semi-finished products that make it more fragile and lead to deformation of the parts.

Therefore, the rubber and polyurethane products maintain their characteristics without major changes for many years if proper storage is guaranteed. In this case the properties of ageing and storage of these products depend heavily on their chemical structure.

Unsaturated elastomers such as nitrile rubber (NBR) can have much shorter shelf life in improper storage conditions than, for example, saturated elastomers such as the fluoroelastomer (FKM).

The ideal characteristics of these products can be maintained for long periods of time only if the products are stored in accordance with the recommendations of DIN 7716.

 

Storage conditions for elastomers and plastics materials

Rubber, plastic and polyurethane products should be stored in a cool, dry place. The storage temperature should be about 15 °C and not exceed 25 °C; relative humidity must be less than 65%.

Rubber, plastic and polyurethane products should not be exposed to direct sunlight and artificial light with a high content of UV.

The storage rooms should not contain any ozone-producing devices such as electric motors or high-voltage devices. It is also essential to protect the seals by hermetic packaging.

The contact between rubber products of different compositions should be avoided. As well as the contact with chemicals and/or hazardous metals (eg copper, manganese) is to be avoided.

The seals must be kept in a state of “tension-free”: the parts should not be subjected to tension, pressure or bending deformation.
If all these recommendations are met, the seals may be retained for the time periods specified below, without losing their characteristics:

 

Trade name	Material	Symbol	Storage
Sealpur	Polyurethane	TPU	about 12 years
Rubseal	Nitril Rubber	NBR	about 5 years
Seaflon	Polytetrafluoro-ethylene	PTFE	about 12 years
Sealite	Polyester Resin	TPE-E	about 12 years
Bearite	Acetal Resin	POM	about 10 years
–	Polyamide	PA	about 10 years
–	Ethylen-propylene	EPDM	about 8 years
–	Hydrogenated Nitrile Rubber	H-NBR	about 8 years
Viton	Fluoroelastomer	FKM	about 10 years
–	Silicone	MQ	about 10 years

NOTE: The above instructions, recommendations and guidelines are listed according to our best knowledge.
However, we can not offer any guarantee and/or responsibility in this regard.