Silicone and Rubber Storage Standards: 8 Ways Silcotech Protects Material Quality Before Moulding

A silicone rubber part can pass every dimensional check on the day it is moulded and still fail months later, because of where it sat in between. Uncured liquid silicone rubber (LSR) that ran past its shelf life, a batch of gaskets left near a window, a stack of seals stored under load: none of these show up on a drawing, and all of them show up as scrap, rework or a field return.

That is why storage is treated as part of the quality system at Silcotech Industry, not a warehouse afterthought. The guidance most rubber manufacturers work from is ISO 2230, the international standard for rubber product storage, alongside DIN 7716. It covers temperature, humidity, light, ozone, deformation, contact with other materials, packaging and stock rotation. If you specify or buy moulded silicone and rubber components, here are the eight storage controls that matter most, and why each one protects the properties you specified.

Why Storage Is a Quality Variable, Not a Logistics Detail

Rubber degrades through a combination of oxygen, ozone, heat, moisture, solvents and UV light. Hardening, softening and surface cracking are the visible result, and they rarely appear on one clean date. For engineers specifying silicone rubber seals, gaskets and medical-grade parts, the practical consequence is simple: a part's durometer, compression set and sealing force are only guaranteed if the part has been stored the way the material was qualified to be stored.

8 Storage Controls That Protect Silicone and Rubber Quality

Keep storage temperature below 25°C. Higher temperatures can shorten service life, and Angst+Pfister's elastomer storage guidance reflects the DIN 7716 and ISO 2230 position that parts should sit below 25°C. In a Malaysian climate, where ambient temperatures regularly exceed that, this means a controlled storage area rather than an open warehouse bay. Below 15°C, elastomers can stiffen, so parts coming out of cold storage should be brought back to working temperature before they are handled or assembled.
Control humidity and prevent condensation. ISO 2230 points to relative humidity below 65%, as summarised by iTeh Standards, though some suppliers quote a 70% ceiling. The more important rule is avoiding condensation, which comes from temperature swings, not from humidity alone. Moisture and mould are the two reasons dark, cool and dry is the standing rule for rubber storage.
Block direct sunlight and high-UV lighting. Martin's Rubber notes that products should be protected from light, particularly sources with high ultraviolet content such as direct sunlight and strong artificial lighting, and recommends covering windows with a red or orange screen. UV exposure attacks the surface first, which is exactly where a seal or gasket does its work.
Keep ozone sources out of the storage room. Ozone is particularly damaging to rubber, so storage rooms should not contain equipment that can generate it. In practice that means keeping parts away from electric motors, mercury vapour lamps and high-voltage equipment, and away from combustion gases and organic vapours.
Hold uncured LSR in sealed original containers, inside datasheet life. Raw material has a much shorter clock than finished parts. For example, Wacker's ELASTOSIL LR 3003/60 datasheet gives a shelf life of at least 12 months below 32°C in the tightly closed original container, while a self-bonding grade such as ELASTOSIL LR 3071/40 is listed at at least 3 months under the same conditions. Shelf life is grade-specific, so the supplier datasheet, not a general rule, sets the limit for each compound.
Store finished parts free from deformation. Rubber should be stored without superimposed tension or compressive stress. A stack of seals under weight or a ring folded into a tight crease can leave a permanent set before the part ever reaches your line. Large-diameter rings are better formed into loops, and sheet material is stored flat or rolled with layers interleaved.
Keep rubber away from liquids, vapours, reactive metals and mixed compounds. Parts should not contact liquids or their vapours during storage, and certain metals and alloys, notably copper and manganese, can have a harmful effect on some rubbers. Contact between products of different compositions should also be avoided, including products that differ only in colour. Dusting powders, where used to prevent blocking, should be kept to the minimum needed.
Rotate stock strictly and respect the shelf-life group. ISO 2230 groups elastomers by expected storage life. Silicone (Q, VMQ and related types) sits in Group C, with a 10-year initial storage period and a 5-year extension after inspection and re-testing, according to the table published by Martin's Rubber. Stock should be issued in strict rotation so that what remains in store is the most recently manufactured. Packaging, inspection and recording are part of the same standard, which is what makes a batch traceable back to when and how it was stored.

What Storage Control Means for the Parts You Receive

For a design or quality engineer, the value of controlled storage shows up in specific places:

Consistent processing behaviour — LSR that has stayed inside its datasheet life and temperature limit behaves the way the process was validated on.
Stable surface and sealing properties — parts kept away from UV, ozone and contaminants arrive without surface cracking, tackiness or discolouration.
True dimensions and sealing force — parts stored without deformation return to specified geometry instead of carrying a set.
Traceable inventory — rotation, labelling and inspection intervals mean a lot can be tied to its storage history if a question comes up later.

These controls matter most for regulated and high-reliability work, such as medical-grade rubber and parts produced through cleanroom manufacturing, where a quality gap cannot be explained away as a warehouse issue.

The Cost of Getting Storage Wrong

A storage gap caught at incoming inspection costs a rejected lot. The same gap caught at first-article inspection costs a re-qualification. Caught after production ramp, it costs a field failure and a corrective-action report. The difference isn't the material, it's whether the supplier treats storage as part of the specification or as someone else's problem.

Contact our team or email info@silcotechindustry.com to talk through your specific application.

Silcotech Industry is a Malaysian precision rubber manufacturer based in Sungai Petani, Kedah, producing silicone and rubber components under ISO 13485 with cleanroom (Class 8 and Class 9) manufacturing.