HDPE vs MDPE
“HDPE” and “MDPE” are two different categories of PE, or polyethylene. HDPE and MDPE are differentiated and categorized into different classes on the basis of density and branching.
Polyethylene
Polyethylene is commonly called polythene. It is a thermoplastic polymer. It is used primarily in the packaging industry to make plastic films, plastic bags, etc. Polyethylene is produced by combining ethane or monomer ethylene. They form long chains chemically and are of different densities. They are classified into different categories depending upon the branching and density. Different PEs have different mechanical properties; these properties depend mostly on the type of branching, extent of the branching, the molecular weight, and the crystal structure. Some of the polythene grades are: HDPE, MDPE, LLDPE, and LDPE.
HDPE
“HDPE” stands for “High-Density Polyethylene.” HDPE falls into the high-density category due to its value being either 0.941g/cm3 or greater than that. HDPE has strong intermolecular forces and high-tensile strength because of its lower degree of branching. It is mainly manufactured by using catalysts like silica or chromium, metallocene, or Ziegler-Natta catalysts. The branching is lowered with the help of catalysts, and the amount of branching can be controlled by using the appropriate catalyst. Branching is also controlled by controlling the reaction conditions.
HDPE has excellent chemical resistance. It has high crystallinity and thus does not dissolve easily. It is resistant to dissolving at room temperature. Because of its characteristics, HDPE is used for manufacturing packaging products, detergents, garbage containers, etc. HDPE has great inertness so it is easy to assemble and has excellent strength when used in manufacturing water and pressure pipe systems. HDPE is also used for making toys; it is believed that almost one-third of the toys in the world are produced by using HDPE.
MDPE
“MDPE” stands for “Medium-Density Polyethylene.” MDPE falls in the medium-density category due to its value being in the 0.926-0.940g/cm3 range. MDPE is manufactured by using catalysts like Ziegler-Natta, chromium/silica catalysts, and metallocene catalysts. MDPE has excellent chemical resistance and is very stable at room temperature. It does not dissolve at room temperature.
MDPE has very good drop resistance and shock resistance. It is less sensitive and has a higher stress-cracking resistance than HDPE. It is used for varied purposes, but some primary usages are for gas pipes manufacturing, carrier bags, packaging film, etc.
Summary:
1.“HDPE” stands for “High-Density Polyethylene”; “MDPE” stands for Medium-Density Polyethylene.
2.HDPE has the density 0.941g/cm3 or greater; MDPE has the density in the range of 0.926-0.940g/cm3.
3.MDPE is less sensitive than HDPE.
4.MDPE has a higher stress cracking resistance than HDPE.