LDPE is an abbreviation for Low Density Polyethylene. Polyethylene is made by polymerization of ethylene. (Poly means ‘a lot’; in fact, it means a lot of ethylene). Ethylene is obtained by cracking a light petroleum derivative such as naphtha.
The low density is obtained by the high-pressure polymerization process. This creates molecules with many side branches. The side branches ensure that the degree of crystallization remains relatively low. In other words, due to their irregular shape, molecules cannot lie in or on top of each other in a well-organized way, so that less of them fit in a certain space. The lower the degree of crystallization, the lower the density of a material.
A good example of this in daily life is water and ice. Ice is water in a (higher) crystallized state, and therefore much heavier than water (melted ice).
LDPE is a kind of thermoplastic. It is a plastic that softens when heated, unlike rubber for example. This makes thermoplastics suitable for reuse. After heating, it can be brought into other desired shapes.
Advantages of LDPE (film)
LDPE is a tough plastic (has many side branches in its molecular structure) that feels quite soft but is still very strong. In addition, it is water-repellent, well-insulating and resistant to acids. LDPE film is therefore very suitable as packaging material. The film may also come into contact with food and can therefore be used in the food industry.
Due to its molecular structure, LDPE is suitable for shrink films. All types of PE shrink when heated in the longitudinal direction of the film. However, the side branches ensure that the film can also shrink in the width direction.
A major advantage of LDPE film is that little material is needed to make packaging. This means that relatively little energy is needed for production. In addition, it also produces less CO2 emissions than other packaging materials because it is so light and has little volume.
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