What is a thermoplastic?
A thermoplastic is a kind of plastic comprised of polymer resins that when heated turn soft and harden on cooling. The neat thing about thermoplastics is that when they are heated the process alters their physical property but not their chemical composition, meaning they can be heated into liquid form that can be reshaped, resized, moulded and always recycled and repurposed. This makes thermoplastic materials incredible desirable in a wide range of industries, both for their flexibility but also their environmentally friendly properties.
There are a wide range of thermoplastics with distinct crystalline structures and densities, meaning there is usually a thermoplastic to suit any particular engineering conundrum and the vast and ever-evolving demands of the plethora of industries with a call for such materials.
Some Characteristics of Thermoplastic Materials
- Strength and durability – excellent strength to weight ratio and unrivalled durability, with high resistance to abrasion, temperature, pressure, and fatigue compared to other plastics or polymers.
- Chemical resistance – very slow to corrode when contacted by liquids or gases & shrink resistant – characteristics making thermoplastics ideal for seals and valves.
- Flexibility – thermoplastic materials are remarkable flexible. Some thermoplastic elastomers can reversibly extend from 5% to 700%; with some even being able to return to their original length after repeated stretching.
The market for thermoplastics
The global engineering thermoplastic market has been estimated at $292.2bn in 2023 and is anticipated to reach $518bn over the course of the next ten years. Serious business and when you consider the properties of this material and the number of industries that make use of it, as well as its recyclable nature, there’s little wonder its such a growth sector.
Thermoplastic injection moulding vs Compression moulding
Primarily, thermoplastics are the domain of injection moulding and compression. The material’s immense flexibility allows experts to mould OEM parts for a wide range of industries. The fact that, as mentioned, thermoplastic does not alter in its chemical composition between heating and cooling allows injection moulding companies to produce vast quantities of parts to exacting standards. Injection moulding is named that because it involves the heated, liquid thermoplastic being injected into a mould cavity and allowed to cool, becoming solid once again. The main difference between injection moulding and compression moulding is that injection moulding moves the material through a screw and a hopper, unlike compression moulding. Compression moulding requires a little extra labour, Injection moulding is more suited to higher volume production while compression moulding is best suited to pliable and flexible materials. Compression moulding is somewhat cheaper.
Where are thermoplastic materials used?
The precision needed for aerospace parts, wind energy, electronics, construction and defence, for instance, makes thermoplastics the ideal material for the job. There are a whole host of industries that take advantage of the unique properties of thermoplastics and the capabilities of the injection moulding sector. Thermoplastics have been credited for transforming the wind turbine industry and in 2020 NREL and Arkema were given a disruptive technology award for their thermoplastic resin system that was developed for wind turbines.