The key difference between HDPE and MDPE is that HDPE has a high sensitivity to stress cracking whereas MDPE has better stress cracking resistance when compared to HDPE.
The terms HDPE stands for high density polyethylene while the terms MDPE stands for medium density polyethylene. Polyethylene or polythene is a polymer material consisting of repeating ethylene units. This material has many applications, most commonly as a packaging material.
What is HDPE?
HDPE is high density polyethylene, a polymer material that forms from the polymerization of ethylene monomers. It is a thermoplastic material (becomes moldable at a specific temperature and solidify upon cooling). This material has a high ratio between strength and density of the polymer material. Therefore, it finds it use in the production of plastic bottles, pipes, etc. The density range for this polyethylene material is 0.93 to 0.97 g/cm3.
The advantages of using HDPE over other polymers include cost-effectiveness, ability to withstand high temperatures, non-leaching properties, resistance to UV radiation, resistance to many chemicals and it is a stiff material. There are some disadvantages as well. The disadvantages include poor weather resistance, flammability, sensitivity to stress cracking, etc.
Some common things people produce using HDPE are as follows:
- Plastic bottles
- Chemical containers
- Pipe systems
- Plastic bags
- Fuel tanks in vehicles
What is MDPE?
MDPE is medium density polyethylene. It is a form of polyethylene that is different from other polyethylene forms according to the density. This material is in the category of thermoplastics. The density range for this material is 926–0.940 g/cm3. Therefore, it is less dense than HDPE.
The most common production strategy for MDPE is the polymerization using Ziegler-Natta catalysts. This material has a considerable shock resistance and drops resistance properties. Apart from that, it has a less scratch resistance when compared to HDPE. However, the stress cracking resistance is higher. This material is used mainly in the production of gas pipes, sacks, fittings, packaging films, carrier bags, etc.
What are the Similarities Between HDPE and MDPE?
- Both are polymer materials that fall under the category of thermoplastics
- They both are forms of polyethylene that differ from each other in their density and properties
What is the Difference Between HDPE and MDPE?
HDPE vs MDPE
|HDPE is high-density polyethylene, a polymer material that forms from the polymerization of ethylene monomers.||MDPE is medium density polyethylene.|
|The density range is 0.93 to 0.97 g/cm3.||The density range for MDPE material is 926 to 0.940 g/cm3.|
|It has a high degree of scratch resistance.||It has a low degree of scratch resistance.|
|The sensitivity to stress cracking is high.||The sensitivity to stress cracking is low.|
Summary – HDPE vs MDPE
Both MDPE and HDPE are forms of polyethylene polymers. These polymers form when ethylene molecules undergo polymerization under different reaction conditions. The difference between HDPE and MDPE is that HDPE has a high sensitivity to stress cracking whereas MDPE, in comparison, has a better stress cracking resistance.
1. “Medium-Density Polyethylene.” Wikipedia, Wikimedia Foundation, 22 Apr. 2018. Available here
2. Plastics. “High Density Polyethylene (HDPE): So Popular.” Plastics Make It Possible, 27 Dec. 2017. Available here