Here at Viking Extrusions, we are often asked ‘what shore hardness should I get for use with…?’. So we thought that it could be good to delve into what exactly the answer is. But before coming to an ultimate conclusion there are a few things that you need to consider.
What is shore hardness and how is it measured?
The shore hardness scale is a measure of the rigidity and hardness of a material and how resistant it will be to permanent indentation. The rubber hardness test is measured by the depth of indentation created on the material with specific force.
Albert Ferdinand Shore defined a durometer scale at which the different shore hardness could be measured against. He developed the shore durometer hardness scale in the 1920s to help measure shore hardness. There are multiple different scales, all ranging from 0-100 with lower numbers indicating a softer material and higher numbers indicating harder materials.
Here at Viking Extrusions, we use the shore A hardness scale which is the scale that is commonly used for different materials like softer plastics and polymers. However, you will also commonly come across shore d scales. Shore d hardness scales measure the hardness of hard rubbers, semi-rigid plastics, and hard plastics.
Viking Extrusions silicone hardness scale
We offer a range of silicones available in as soft as 10° Shore A scale 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 ‘snakeskin’ effect. 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 sealant is needed. 70A durability offers great abrasion resistance for o-rings while also maintaining its sealing capabilities in extreme applications.
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.