What is polyethylene (PE)?
PE, or ethylene polymers, are a family of thermoplastics widely used because of their low cost and versatility. Their remarkable properties, which include excellent chemical resistance, make them ideal for a wide range of applications in a multitude of industries. The polyethylene family can be divided into different types of compounds, including LDPE (low-density polyethylene), HDPE (high-density polyethylene) and UHMW-PE (ultra-high-molecular-weight polyethylene), all three of which will be discussed in this article.
The advantages of polyethylene
Of all polymers, polyethylene compounds are by far the most complete in terms of properties, which differ according to their molecular weight. It is therefore possible to choose a polyethylene that is best suited to a specific application. As a general rule, this family of plastics possesses good chemical resistance, is inexpensive and noticeably light. However, it is important to evaluate the advantages specific to each type of polyethylene to better understand their value and maximize their use.
The different types of polyethylene
LDPE (low-density polyethylene)
LDPE is a relatively supple plastic that is more flexible than HDPE or UHMW. It does, however, possess inferior mechanical strength, making it less suitable for demanding applications that require high-performance plastics.
As it is significantly more flexible than HDPE or UHMW, LDPE is used for other types of applications, such as
- packaging material,
- medical prostheses,
- thermoformed components, and
- impact plates.
HDPE (high-density polyethylene)
This plastic possesses mechanical properties superior to those of standard polyethylene. As its name suggests, HDPE is denser than LDPE and is therefore harder and stiffer. It can be moulded or welded and possesses properties that make it more suitable for applications in the food, pharmaceutical and chemical industries. It is also a popular material for the design of chemical-resistant tanks. The main advantages of HDPE include its
- good chemical resistance (especially to alcohols and solvents),
- good impact resistance,
- mechanical properties suitable for a wide range of applications,
- food grade certification,
- low water absorption, and
- light weight.
Because of its hardness and rigidity, HDPE is mainly used in applications that require a strong yet affordable material. HDPE applications include
- cutting boards,
- conveyor components,
- thermoformed parts,
- chain guides, and
- medical prostheses.
UHMW-PE (ultra-high-molecular-weight polyethylene)
UHMW is often confused with Teflon (PTFE) because of its low coefficient of friction. Although these two materials have similar properties, UHMW rather compares to HDPE in terms of mechanical properties. Like HDPE, UHMW is also available in food grade. It is a high-performance polyethylene specifically designed for demanding applications frequently subjected to friction and impacts. For this reason, UHMW is an ideal plastic to manufacture anti-friction liners that reduce wear and impact noise. The main advantages of UHMW include its
- good chemical resistance (some grades can tolerate temperatures up to 135 °C [275 °F]),;
- excellent mechanical properties,
- low coefficient of friction (some grades have a coefficient of friction as low as 0.08), and
- food grade availability.
UHMW is the material of choice for applications that are too demanding for HDPE, as it is specifically designed for extreme environments. It is mainly used to manufacture
- conveyor components,
- noise-reducing liners,
- anti-friction liners,
- dissipative parts,
- wear resistant chain guides,
- food machinery components, and
- transfer belts.