What is notch sensitivity and why is it important?

March 30, 2022

Roto Moulding

Notch sensitivity is a pretty key consideration in plastic manufacturing, but it’s safe to say that it’s a pretty niche term for everyone else, especially since it’s not very widely used outside the manufacturing sector. So before we go into the various reasons why it’s so important, let’s get you up to speed with a quick refresher on exactly what we mean by the term.

To give you the technical definition, ‘notch sensitivity’ measures the extent to which a plastic product’s structural integrity is weakened by ‘stress-causing notches’ in its structure. In other words, how much more likely it is to break when it’s already sustained scratches, cracks, or holes in its body.

As a general rule, the more ductile a given material is, the lower its notch sensitivity tends to be. Low-density polyethylene, for example (the sort used for plastic bags and panelling) has a low notch sensitivity, whereas medium and high density polyethylene (MDPE and HDPE) are both slightly more brittle materials, which gives them a higher notch sensitivity. However, their chemical makeup equally makes them more resistant to sustaining damage in the first place, so it’s not a zero sum calculation!

Why is notch sensitivity important?

Notch sensitivity is worth taking into account for any plastic product, as it contributes to its overall durability – and as everyone knows, the most durable plastic products are more sustainable, more versatile, and provide better value for money. So while notch sensitivity is a relevant consideration whatever the nature of your plastic product, it’s exceptionally important for a safety-critical product, such as a set of our plastic safety steps.

In a nutshell, if your plastic product is used in more active settings such as the great outdoors or in sporting environments, there’s a higher chance that it’s going to be subjected to sudden shocks through knocks, bumps or other casual impacts. And if a human being is using it at the time, especially if it’s taking the weight of their body (such as the aforementioned safety steps), then it could have safety implications – a structural failure could all too easily end up leading to injuries.

That makes notch sensitivity a crucial consideration, as any defects or damage to the plastic’s structural integrity must be immediately (and if necessary, continually) evaluated to ensure they don’t contribute to a tangible threat to human health and safety.

Active environments aren’t the only settings where notch sensitivity is particularly important. It’s also a constant priority for agricultural settings, where plastic tanks might be used to store liquids, foodstuffs, and even livestock. Even a small crack in one of the plastic tanks we created for the Scottish Salmon Company would be a major cause for concern – if it widened into a serious breach, it could lead to the death of every fish in the tank.

So what about your plastic product?

When you choose us here at Excelsior to help you create your plastic product, one of the first discussions we’ll have with you will focus on exactly how you intend your product to be used, and by extension, what sort of casual wear and tear might it be expected to endure on a regular basis. This can then inform our decisions on its build, shape, and exactly which material to use – we predominately work with MDPE and HDPE, and use our roto-moulding process to bring your product to life.

We’ve now got more than a century of experience behind us here at Excelsior, giving us more than 100 years of passion and expertise that we can use to ensure that your product is durable, economical, and practical – so that your plastic product provides you with the very best return on investment. Just take a look at some of our successful case studies for previous clients, or give us a call on 0161 765 2010 to see what we can do for you!