At Viking Extrusions Ltd, we offer a wide variety of silicone compounds that are available in various hardnesses to suit a multitude of applications. A common question our customers ask is, “What shore hardness should I get for use with ……?” To elaborate on the right answer to that question, we would like to give our customers a better understanding of how a shore hardness is measured, how it affects the final product, and how best to make the most educated decision to choose the correct option.
What is a shore hardness and how is it measured?
Simply speaking, shore hardness is a measure of the rigidity of a given material and how resistant it will be to permanent indentation. It is measured by the depth of indentation that is created on the material with a specified force. Albert Ferdinand Shore, defined a durometer scale at which this could be measured against. In the 1920s, he developed a device (also commonly known as a durometer) to measure Shore Hardness. There are several scales of hardnesses, all ranging from 0 to 100 with higher values indicating a harder material. Viking Extrusions uses the Shore A scale which is a common scale for softer plastics and polymers.
We offer a range of silicones available in as soft as 10° Shore A up to 80° Shore A in increments of 5° Shore A.
Because our 10° Shore A material is so soft, as it is extruded, the material tends to catch slightly through the die design which causes a minor ‘snake skin’ affect. Whilst this doesn’t affect the quality of the product, the rougher skin can affect it visually and if your product is to be used in a location that it is visible, we would recommend you choose a slightly harder option to prevent this.
20° Shore A can easily be compared to the hardness of a rubber band. The material extrudes smoothly and is a great option for soft, visible applications. It is one of our lesser used compounds but may be a good option for your requirements.
40° Shore A is similar to the hardness of a pencil eraser. This is flexible and a good option for a variety of seals and applications.
Our most common option is 60° Shore A which is applicable to many tubes, profiles and gaskets. It is the material we use for our inflatable seals as we have found that the material expands more evenly compared to softer materials which tend to create ‘bulbs’ in the profiles during inflation and harder materials which tend not to be as malleable.
70° Shore A can be compared to that of a tire tread. Whilst still malleable, this material works well for applications where a harder seal is needed.
The hardest material we currently offer is 80° Shore A which is as hard as an average shoe heel. This is a great product if you’re seeking a rigid product to replace a plastic component. Whilst it’s not as hard as plastic, it is a great alternative.
Whilst it can be difficult to make the right decision, you can give us a call and request a few samples to display each shore hardness we can offer. Silicone Rubber is an incredibly versatile polymer and offers a resilient, affordable option to a variety of applications in a multitude of industries from simple edging strips for use in engineering, to complex hatch profiles for use in automotive production, to inflatable seals for use in pharmaceutical, marine, nuclear, aeronautics, packaging and many more. Tooling needed to produce a new prototype extrusion is affordable and costs of scaling up to larger production orders are manageable. In many cases, we’re able to turn over orders in a matter of days so if you’re in a rush, we will make every effort to accommodate you.