Manufacturers using silicone rubber products have to find the right balance between having enough stock on hand and shelf-life limitations. On the one hand, they must maintain sufficient stock levels to respond in time to customer demand and avoid supply-chain disruptions. On the other hand, they must use the silicone rubbers they have before their expiry dates to ensure they provide proper performance.
So, how close to the expiry date can silicones be used or can they even be used beyond? Storage conditions are the primary factor affecting the quality and shelf life of rubber products. If stored suitably, silicone rubbers generally maintain their main performance features for an average of six months, and up to 12 months in certain cases.
It’s best to use the silicone products as early as possible and to test their performance characteristics before they enter the manufacturing process. In some cases, even if the shelf life has expired, silicone rubber products can still be used, but should be carefully evaluated for possible use as originally intended. This avoids discarding products solely on the basis of their suggested shelf life.
Our challenge was to support our customers in managing their silicone stocks and to provide them with the expertise to evaluate the performance characteristics of their products during the entire shelf life and, when possible, beyond the expiry date.
To begin with, it’s important to understand why and how silicone rubbers deteriorate. In fact, the main change is a rise in what is called Mooney viscosity. This means that the polymer and filler interact more over time, leading to decreased viscosity or hardening. This phenomenon can be amplified when additives are blended into the silicone rubber for processing in extrusion or compression molding.
Regenerating the original characteristics is possible for these processes, using various techniques such as replasticating or mastication, but this can only be done in certain cases. The challenge was therefore to establish an evaluation and transformation service that could reliably decide whether silicones could be used in specific applications beyond their expiry date.
Elkem Silicones provides a Reprocessing Service to its clients through its Mix&Fix Center™, conveniently located in Europe (sites in Italy and Spain), China and North and South America. Customers can send samples of their silicone rubber compounds to these centers and explain the characteristics needed for the use of their stocks.
Elkem Silicones experts analyze these samples to see if they are reusable in their current state or if they can be reprocessed. In the latter case, customers send their stock to a designated processing plant and Elkem Silicones reworks the products to restore temporary their original mechanical characteristics.
When this is not possible, the customer is informed of the situation and, in some cases, other alternatives can be found case by case. Elkem silicones can advise customers of how to use the products for other applications or, if when this is no longer possible, how to dispose of stocks in the cleanest and most economical way.
In all cases, the Reprocessing Service is always available to make sure that silicone compounds are properly used, recycled or disposed of in an environmentally safe way.
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