LDPE stands for Low Density Polyethylene, also called Low-Density Polyethylene in English. Many users and producers still refer to ethylene instead of ethylene.
Polythene is formed by polymerisation of ethylene (poly means "many"; literally, therefore, many-ethene). Ethylene is obtained by cracking a light derivative of petroleum, such as naphtha.
The low density of LDPE results from carrying out the polymerisation process under high pressure, creating molecules with many side branches. These side branches lower the degree of crystallisation, meaning that the molecules do not lie tightly together due to their irregular shape. This causes fewer molecules to fit in the same space, resulting in a lower density of the material.
We see a good example of this effect with water and ice. Ice, being in a more crystallised state, is lighter than water.
LDPE is a thermoplastic, a type of plastic that softens when heated, unlike rubber, for example. This allows LDPE to be easily reused and moulded into other shapes after heating.
Advantages of LDPE (film)
- Strength and flexibility
LDPE is a tough plastic with many side branches in its molecular structure. This gives the material a soft texture, but at the same time it offers high tensile strength and tear resistance. This combination makes LDPE film particularly suitable for packaging solutions where both flexibility and toughness are important, such as shrink wrap and stretch films.
- Water-repellent and chemical-resistant
Thanks to its hydrophobic properties, LDPE offers excellent protection against moisture and other liquids. This makes it ideal for applications where water resistance is required, such as when packaging building materials or garden products like potting soil. In addition, the material is resistant to a wide range of chemicals, including acids, bases and oils, contributing to its versatility.
- Suitable for the food industry
LDPE is safe for direct food contact, which makes it perfect for applications in the food industry. It is often used for packaging such as freezer bags, cling film and bakery packaging, where hygiene and food safety are crucial.
- Thermal properties
The molecular structure of LDPE makes it very suitable for applications such as shrink wrap. Whereas other types of polyethylene shrink mainly lengthwise when heated, LDPE can also shrink widthwise due to its side branches. This ensures an optimal and uniform fit around products, which is essential when packing, for example, pallets or bundles.
- More environmentally friendly than many alternatives
A major advantage of LDPE is that less material is needed to make a sturdy packaging. This leads to less use of raw materials, lower energy consumption during production and a smaller carbon footprint. Moreover, the light weight contributes to more efficient transport processes, further reducing environmental impact.
- Recycling LDPE film
LDPE film is highly recyclable, if collected and processed correctly. Recycled LDPE (PCR: Post-Consumer Recycled) can be used to produce new films or other plastic products, such as rubbish bags or construction films. This makes LDPE a circular material that helps reduce plastic waste and contribute to a more sustainable packaging chain.
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