Polyethylene or polyethylene is one of the simplest and cheapest polymers. Polyethylene is a waxy and inactive solid. It is obtained by polymerization of ethylene and is abbreviated as PE. The ethylene molecule () has a double bond C = C. In the double polymerization process, each of the monomers is broken, and instead a simple bond is formed between the carbon atoms of the monomers, and the resulting product is a large molecule.
Types of polyethylene
Polyethylenes are classified based on their density, which is involved in the amount of density, the size of the polymer chain and the type and number of branches in the chain.
HDPE (High Density Polyethylene)
This polyethylene has branched polymer chains, so the intermolecular strength in the chains is high and its tensile strength is higher than other polyethylenes. The reaction conditions and the type of catalyst used in the production of HDPE polyethylene are effective. For the production of branched polyethylene, the polymerization method with Ziegler-Nata catalyst is usually used.
LDPE (Low Density Polyethylene)
This polyethylene has branched chains so LDPE chains can not bond well with each other and has weak intermolecular strength and less tensile strength. This type of polyethylene is usually produced by radical polymerization. The properties of this polymer are flexibility and the possibility of degradation by microorganisms.
LLDPE (Low Density Linear Polyethylene)
This polyethylene is a linear polymer with a number of short branches and is usually formed by the copolymerization of ethylene with long chain alkenes.
MDPE (Medium Density Polyethylene)
Another type of polyethylene is medium density polyethylene.
Polyethylene is widely used in the production of various plastic appliances used in the kitchen and food industries. LDPE is used in the production of lightweight plastic containers as well as plastic bags. HDPE is used in the production of milk and liquid containers and all kinds of plastic kitchen utensils. MDPE is commonly used in the production of plastic pipes and piping fittings.
Due to its high degree of flexibility, LLDPE is used in the production of a variety of flexible plastic devices such as bendable tubes. Recently, many researches have been done in the production of long-chain polyethylenes with short branches. These polyethylenes are originally HDPE with a number of side branches. These polyethylenes have a combination of HDPE strength and LDPE flexibility.