Plastic melts when you heat it to a certain temperature. The shape of the plastic then changes, and it becomes soft when you heat it. However, this depends on the type of plastic you use. Some plastics become soft when you heat them, while others become liquid when you heat them.
Like steel, there are numerous plastics, each with different properties and melting points. A plastic kettle is therefore designed not to melt when water boils in it at 100°C. Typically, kettles are made of Polypropylene, or PP. PP has a melting temperature of 160°C, which means it starts to melt around 130°C. More than enough for a water boiler!
Below the information of the different melting points of some types of plastics.
Polyethylene or LDPE & HDPE
Polyethylene (PE) is a soft polymer found in the two main types LDPE & HDPE. At higher temperatures, this plastic loses its rigidity and begins to melt. LDPE will already begin melting at 105°C and HDPE will begin melting at 125°C. Polyethylene is used in the fabrication of packaging films, bags & sheets among other things. Would you like more information about the manufacturing of LDPE & HDPE? Then contact us, we have been manufacturing LDPE & HDPE flexible plastics for over 50 years!
Polypropylene (PP) is a slightly harder and stiffer plastic than HDPE (PE) plastic, it therefore has a higher melting point of 165°C. Polypropylene is a type of plastic that loses its properties faster at lower temperatures. It is therefore used for coffee cups, plastic tableware and durable household items.
Polystyrene (PS) is a hard polymer used in the manufacture of the well-known polystyrene foam. This plastic does not require a high melting point, which is why it melts at around 90°C.
Polyamide (PA) is also popularly known as nylon. Polyamides have a fairly high melting point of 200°C. The only disadvantage of Polyamide is that it is weakened by water. Therefore, due to its fabric-character, polyamide is often used for the manufacture of clothes.
Polyvinyl chloride (PVC)
PVC is a well-known type of plastic, it has many applications such as sewage, floor coverings, components in the medical field, insulation and many more. Because PVC is largely used in industry, it must be very strong, but also have a high melting point. PVC therefore has a melting point of around 210°C.
Mixing plastics with other plastics
When types of plastics are mixed with impurities or other applications (think of the use of recycled material or when different plastics are mixed), the plastic may lose its properties and become less strong. Also the melting point of the plastic that is mixed can be lower. However, it depends on the amount of impurities how much the plastic loses its properties and how much lower the melting point is afterwards.