Linear Low-Density Polyethylene Structure

Written by krista niece
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Linear Low-Density Polyethylene Structure
LLDPE is widely used in packaging applications. (wrap image by Allyson Ricketts from

Polythene (PE) is a versatile plastic with applications ranging from low-cost disposable bags to heat- and chemical-resistant automotive parts. Linear low-density polythene (LLDPE) is a type of polythene widely used in coatings, films and packaging materials due to its ease of processing, low cost and relative durability.

Chemical Structure

Polythene has a very simple and stable chemical make-up. Made up of inert hydrocarbons, PE chains have few reactive sites that can serve as breakage points. For this reason, PE products tend to be very sturdy and nondegradable.

Linear Low-Density Polyethylene Structure
Polythene chains are uniform and can pack closely together in high-density PE. (rope image by Antons Trifonovs from


All types of polythene (which include high-density, low-density, ultra-high molecular weight and others in addition to LLDPE) have the same chemical structure described above. The difference between them is the chain structure. Chains of low-density polythene (LDPE) are highly branched, creating a disorganised polymer structure in which the close packing and chain interactions characteristic of high-density polythene are hindered. Although the strength and stiffness of the PE is greatly compromised by this change in structure, the processing difficulty is greatly decreased, making LDPE ideal for low-cost applications that don't require the strength of high-density polythene.

Linear Low-Density Polyethylene Structure
LDPE chains are highly branched, leading to a bushy structure. (d_tree_sunrise2 image by Sergey Tokarev from


LLDPE differs from regular LDPE in that its structure, though branched, is more highly controlled. In LDPE, each branch can be branched in turn, leading to a bush-like structure. LLDPE, on the other hand, consists of long, linear polymer chains with short, unbranched side-chains. Like knots in a rope, these side-chains prevent close packing of the chains while preserving chain length, leading to improved mechanical properties over LDPE while maintaining its ease of processing.

Linear Low-Density Polyethylene Structure
Like knots in a rope, the side-chains of LLDPE prevent close packing with adjacent chains. (rope knot image by Galyna Andrushko from

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