How Long can Rubber Products be stored for?

Introduction

All rubber products have a weakness, whether it be temperature, exposure to sunlight, or another, and different rubber compounds have different weaknesses.

The simple answer to this question calls upon ISO 2230 which gives a good-but-broad answer through a simple framework

Before you start, know which rubber you are looking at.
Which group (A-C) does your rubber belong to
What are the recommended storage times for that group
What are the assumed storage conditions.

So, let's get started.

Rubber Groupings under ISO 2230

Group A rubber compounds include:

Common Rubber Compound Name	Abbreviation for Compound	Chemical Name (ISO 1629)
Natural Rubber	NR	Natural Rubber
Polybutadiene	BR	Butadiene Rubber
Polyisoprene	IR	Isoprene Rubber Syntetic
SBR	SBR	Styrene-Butadiene Rubber
Polyurethane	AU	Polyester Urethane Rubber
Polyurethane	EU	Polyester Urethane Rubber

Group B rubber compounds include:

Common Rubber Compound Name	Abbreviation for Compound	Chemical Name (ISO 1629)
Nitrile	NBR	Acrylonitrile-Butadiene Rubber
Carboxylated Rubber	XNBR	Carboxylic-Acrylonitrile-Butadiene Rubber
Hydrogenated Nitrile	HNBR	Hydrogenated NBR
Neoprene	CR	Chloroprene Rubber
Butyl	IIR	Isobutene-Isoprene Rubber
Bromobutyl	BIIR	Bromo- Isobutene-Isoprene Rubber
Chlorobutyl	CIIR	Chloro- Isobutene-Isoprene Rubber

Group C rubber compounds include:

Common Rubber Compound Name	Abbreviation for Compound	Chemical Name (ISO 1629)
Chlorinated Polyethylene	CM	Chloropolyethylene
EPM, EPR	EPM	Ethylene-Propylene Copolymer
EPDM	EPDM	Terpolymer of Ethylene, propylene and diene with the residual unsaturated portion of the diene
Fluorocarbon	FKM	Rubber having the Fluoro, Perfluoroalkyl or Perfluoroalkoxy substituent groups on the polymer (a common example is Viton)
Silicone	Q	Silicone Rubber
Fluorosilicone	VMQ	Silicone Rubber having both Methyl and Vinyl substituent groups on the polymer chain

Recommendation storage limits for each Rubber Group

Once we know which group our rubber is in, we can look it up in the below table:

Rubber Group	Initial Storage Period	Extension Storage Periods
Group A	5 years	2 years
Group B	7 years	3 years
Group C	10 years	5 years

The initial storage period is a given, if stored correctly. At this point the products should be inspected. If the parts look unchanged, then the extension period can be applied.

If your rubber is a blend of two different groups, use the shorter timescales, if applicable.

Rubber Storage Conditions

ISO 2230 specified the storage conditions for rubber products to ensure their longevity and to prevent deterioration. These conditions include maintaining a cool, dry environment, protecting against light and UV radiation, and preventing exposure to ozone.

Specifically, storage temperatures should be below 25°C (preferably below 15°C), and relative humidity should be kept below 70% (65% for polyurethanes). Additionally, products should be protected from direct sunlight, strong artificial light and ionising radiation.

Common Issues Faced with Rubber Storage

There are a few common issues we are asked about, and face internally with our own products:

What if I receive multiple batches at different times? The answer to this one is that you can ask your supplier when different batches were cured/vulcanised. If the dates are similar, then many companies will combine the storage and inspection cycles should date thresholds be met. If the dates are notably different then the different batches should be kept separate.
My supplier cannot be specific about when my products were manufactured. Suppliers should be able to tell you this information. If they cannot, are you sure that they are manufacturing them rather than reselling them?
I am not sure what my rubber is, what should I do? Ask your supplier, this information should be readily available.
I have received parts that were moulded a year ago. What does that mean for my timelines? In this case, you should knock off a year from the timeline.