What are thermoplastics, and what makes them so useful?

April 29, 2019


It’s a question that our experts get asked by our customers here at Excelsior, and it’s hardly surprising why! Many of the core materials we use here at Excelsior are classed as thermoplastics, which we use to fulfil a wide range of customer orders, including (to name just a few examples) safety steps, container bins, or even bespoke plastic products. Lots of these wouldn’t be possible without thermoplastics, so this week, we thought it was worth a brief explainer on exactly what thermoplastics are, and why they’re so helpful.

What are thermoplastics?

Like many substances, thermoplastics melt when they’re subjected to heat. What makes them unique compared to other plastics, though, is that they can be melted and reformed multiple times before they start to lose their strength and integrity. This is essentially largely due to their molecular structure, which comprises long chains of repeatable molecular units – allowing them to be melted, reformed and frozen quite easily.

In fact, our own rotomoulding method of plastic manufacturing is designed around this capability. In a nutshell, the process involves placing a thermoplastic within a hollow tool, which is manufactured from sheet steel. This tool is then placed in an oven chamber, which heats up to temperatures somewhere between 220°C to 350°C.


The intensity of the heat melts the thermoplastic inside into a viscous, liquid phase. As this change occurs, the tool is rotated on two axes at low speeds, using centrifugal force to distribute the liquid plastic evenly around its interior walls. There, the thermoplastic cools and hardens, before finally being removed from the tool; resulting in a hollow plastic product with a consistently even wall thickness.

The effectiveness of this technique is well known, and indeed alongside injection moulding, it’s one of the most common methods of processing thermoplastics.

Why are thermoplastics so useful?

The process we described above wouldn’t be possible without the unique ability of thermoplastics to maintain their structure as they undergo the change from a solid to a liquid state, and then back into a solid again. Here are just a few of their other key advantages:

Economical and cost-effective

Thermoplastics allow for a high level of energy efficiency, both in terms of manufacturing and processing. Their pliability ability to be melted down and reformed multiple times allows for plenty of reprocessing and recycling. This in turn cuts down on the demand for new raw material, making them economical to manufacture, and cost-effective for customers.

Highly versatile

The term ‘thermoplastics’ encompasses several different individual materials, from flexible, pliable Low Density polyethylene all the way up to the toughest High Density polyethylene. This means that collectively, themoplastics are a highly versatile group of materials, giving customers a range of options to choose the material that best suits their vision for their plastic product.

Lightweight, durable and high-strength


Thermoplastics allow for the creation of large plastic products which are reasonably lightweight for their size, allowing for maximum practicality and safety – particularly useful for products like safety steps or equestrian products. Their durability gives them a long operational lifespan, while their strength can be measured in several ways. Low Density Polyethylene, for example, tends to have a high tensile strength, so that it can be pulled and stretched quite a bit before tearing, while HDPE can take a lot of physical punishment from casual knocks or bumps, making it ideal for piping or containers.

Collectively, these core benefits mean that thermoplastics have a wide range of applications in an array of sectors and industries. If you’ve got an idea in mind for your own plastic product, here at Excelsior we’re only too happy to help. Feel free to give us a call on 0161 265 2010, and we’ll see what we can do for you!