Difference between Polypropylene and Polyethylene

By Jaxson

Main Difference

The polyethylene is a polymer that is made just due to the procedure of the polymerization of ethylene molecules. These molecules are two Carbon Alkane units represented in the form of [-CH CH -]. It is a form of a thermoplastic polymer. This is the molecular weight of the polyethylene which will decide its physical properties. The major types of the polyethylene are known as the High Density Polyethylene (HDPE), Medium Density Polyethylene (MDPE) and the Low Density Polyethylene (LDPE). The nature of the polyethylene is the thermoplastic polymer that is more inflexible than that of the polyethylene. The polypropylene, on the other side, will come to existence just because of the presence of the propylene monomer units having three Carbon alkane units in the shape of [–CH (CH) CH -]. The utilization of the polypropylene can be seen in the making of molded material by and large just because of its rigid nature.


In the world of today, the most common plastic used is made up of Polyethylene. A polymer that is made up of ethylene is called the Polyethylene. It is the nature of the ethylene that it contains two carbon atoms that are well bonded to each other with a double covalent bond and each carbon is attached with two hydrogen atoms because of the presence of bond. A new sigma bond between two carbons of two ethylene molecules takes place in the situation of polymerizing in which the double bond is broken. As an outcome, you can say that the polyethylene can be produced only in the condition when an addition reaction of the monomer ethylene is occurred and the repeating unit is –CH – CH – will come. The nature of the structure of it is very simple with long chain carbon atoms. The properties of the synthesized polyethylene will not be the same in every case as it will change just according to the method of the polymerization. Therefore, you can find them in the shapes of the straight chain and branch. This is the Branched polyethylene shape this is easy to make and economical in nature. But on the other hand, the strength of the Branched polyethylene is much lower than that of the straight chain polyethylene. You can observe the immense utilization of the Polyethylene in the process of making bottles, bags, toys and lots of other things used in every corner of the globe.


The nature of the Polypropylene is a plastic polymer too but when you check its monomer, you will come to identify that it is propylene, having three carbons and one double bond between two of those carbon atoms. The manufacturing process of the Polypropylene includes the propylene gas which is used in the presence of a catalyst like the titanium chloride and many others. The production process of the Polypropylene is very simple and trouble free and it has the ability to be manufactured with high purity as well. The characteristics of the Polypropylenes will show you that they are light in weight, have a high resistance to cracking, acids, organic solvents and electrolytes. The melting point of the Polypropylene is high and it is well furnished with the good dielectric properties and is non-toxic in nature. It has a high economical value and widely used for the purpose of making the pipes, containers, house ware, packaging, and automotive parts in general.

Key Differences

  • They both have different monomer. In the polyethylene, you will find the ethylene while in the polypropylene, you will observe the propylene.
  • As compared to the polypropylene, the melting point of the polyethylene is low.
  • The polyethylene is stronger than that of the Polypropylene.
  • The polyethylene is less stiff and resistant to the chemicals and organic solvents while comparing with the Polypropylene.
  • The polyethylene is less pure, non-stretching and rigid than that of the Polypropylene.

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