Thermo Plastics

The next few blogs that I will be posting, will be regarding different types of plastics and different processes we will undertake in the workshop during our clock making process. This first blog is on Thermo Plastics.

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A thermoplastic is a type of plastic made from polymerresins that becomes a homogenized liquid when heated and hard when cooled. When frozen, however, a thermoplastic becomes glass-like and subject to fracture. These characteristics, which give the material its name, are reversible. That is, it can be reheated, reshaped, and frozen repeatedly, Which additionally makes thermoplastics recyclable. Heading into more detail about why Thermo Plastics can be recycled is because the weaker interactions between polymer chains break down at much lower temperatures than the chemical bonds between monomers. This allows thermoplastics to be recycled indefinitely until the polymers are broken down to the point that the material loses structural integrity.

Thermo Plastics are different from Thermosetting Plastics however, as on heating this type of plastic, it does not undergo a chemical change, whereas Thermosetting Plastics do. Additionally, Thermo Plastics cannot resist heat very well and therefore can easily be formed into other shapes, making it one of the most common materials used in the school workshop. A moulded sheet of Thermo Plastic that has been formed into a shape can be reheated and it will return to its original shape. This occurrence is referred to as plastic memory.

Examples of Thermo Plastics include Polyamides (or nylon), acrylics and Polystyrene (as shown below). As Polyamides is tough and resists abrasion, as well as being self-lubricating, makes it ideal for ropes, fishing line, gears and zips. Acrylics have good impact strength and transparency, which is why it is most often used in goggles, windows and lenses. Polystyrene is easy to use, and comes in many colours, making it an ideal material to use in packaging trays, vending cups and ceiling tiles.

Polystyrene - in this case in the form of a disposable cup.

Sometimes, thermoplastics are confused with Thermosetting Plastics. Although they may sound the same, they actually contain very different properties. While Thermo Plastics can be melted to a liquid and cooled to a solid, Thermosetting Plastics chemically deteriorate when subjected to heat. Ironically, however, Thermosetting Plastics tend to be more durable when allowed to cool than many thermoplastics.

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Thank you very much for reading and keep posted for more useful information!