Rubber Storage Conditions
Most of the rubber made parts change in physical properties during storage and ultimately become unserviceable, for example, leads to excessive hardening, softening, cracking, crazing, or other surface degradation.
These changes may be the result of one particular factor or a combination of factors, such as the action of oxygen, ozone, light, heat, humidity or oils and solvents. The deleterious effects of these factors may, however, be minimized by careful choice of storage conditions.
The storage temperature should preferably be between 5°C and 25°C because at higher temperatures deterioration occurs more readily. Sources of heat in storage rooms should be so arranged that the temperature of stored articles never exceeds 25°C.
The effects of low temperature are not permanently deleterious to rubber articles by they may become stiffer if stored at low temperatures and care should be taken to avoid distoting them during handling at that temperature.
When articles are taken from low temperature storage for immediate use their temperature should be raised to approximately 30°C throughout before they are put into service.
The relative humidity in the store room should be below 75%. Very moist or very dry conditions should be avoided. Where ventilation is necessary it should be kept to a minimum. Condensation should not occur.
Rubbers should be protected from light, in particular rather than strong sunlight and strong artificial light with a high ultra-violet content. Unless the articles are packed in opaque containers it is advisable to cover any windows of storage rooms with a red or orange coating or screen.
Oxygen & Ozone
Whereever possible, rubber should be protected from circulating air by wrapping, storage in airtight containers or by other suitable means. This particularly applies to articles with large surface area to volume ratios, for example proofed fabric, cellular rubber.
As ozone is particularly deleterious, storage rooms should not contain any equipment that is capable of generating ozone, such as mercury vapor lamps, high voltage electrical equipment, electric sparks or silent electrical discharges.
Rubbers should, wherever possible, be stored in a relaxed condition free from tension, compression or other deformation. Large O-rings and seals must not be suspended on pegs as this will lead to severe deterioration.
Where articles are packed in a strain-free condition they should be stored in their original packaging.
Contact with Liquid & Semi-Solid Materials
Rubbers should not be allowed to come into contact with solvents, oil, greases or any other semi-solid materials at any time during storage, unless so packed by the manufacturer. In certain cases rubber components may require to be stored coated with the fluid in which they are to be used.
Contact with Metal
Direct contact with certain metals, for example manganese, iron, copper and its alloys are known to have deleterious effects on some rubbers.
Rubber should not be stored in contact with such metals, or materials impregnated with their compounds, but should be protected by wrapping or separation with a layer of suitable material, for example paper, polythene.
Contact with Non-Metals
Because of possible transfer of plasticisers or other ingredients, rubbers must not be stored in contact with P.V.C.; different rubbers should preferably be separated from each otehr. Contact with creosote-impregnated timber or fabrics should be avoided, also compounds containing copper naphthenate and sulphur.
Where necessary, cleaning should be carried out with the aid of soap and water. Water should not, however, be permitted to come into contact with fabic reinforced components or polyurethane rubbers. Disinfectants or other organic solvents must not be used. After cleaning, the article should be dried at room temperature and not placed near a source of heat.
Lip type seals should always be stored in such a way as to prevent the sealing edges being damaged. On no account should identity labels be tied to the actual components.
If the items are carefully stored as recommended their shelf life is generally very long. Where there is any reason to think that storage conditions are less satisfactory than those recommended representative samples from each batch should be inspected and tested in accordance with the paragraph on expire of the periods listed below, but in any case every detail should be tested immediately before assembly the component.
Natural rubber, Nitrile, Polyurethane, Styrene-Butadiene, Polyacrilate, Neoprene. Intial period 5 years extention period 2 years
- Ethlene-Propylene, Fluorocarbon, Fluorosilicone and Silicone - 10 years.
Methods of Inspection & Test
The rubber and unassembled rubber details should be given a careful examination for:
(a) Permanent distortion, mechanical damage, flats or other defects.
(b) Tackiness or noticeable surface softening or hardening.
(c) Cracks (using a hand lens when the rubber is extended or flexed)
Note: During storage, degradation by oxidation may occur. This first appears as a surface defect and may have serious consequences. The usefulness of a rubber component will be related to the ratio of total thickness of the degraded layer.
Surface degradation may therefore be far more serious on a thin rubber section than on a thick rubber section. The appearance of a "bloom" is unimportant and is not evidence of degradation.
Product Safety Data
The materials used in the production of the seals and components are not dangerous.
1. Hazard warning: not required.
2. First-aid measure: no special measures required.
3. Fire-fighting measures:
Extinguishing measures: water and extinguishing foam. Generation of toxic gases / fumes in case of fire, use breathing apparatus.
4. Handling and storage: Store in a dry place; no special measure for handling conditions.
5. Toxilogical information: According to experience no harmful effects are to be expected under proper handling conditions.
6. Ecological information and disposal: Approved incineration plant or disposal site, according to local regualtions.
7. Transport: No dangerous goods according to transport regulations. Do not store together with food.
8. Regulation: No labelling is required in accordance with the E.E.C. directive.