UHMW and HDPE are thermoplastic polymers with a similar appearance. the main difference between UHMW and HDPE is that UHMW contains long polymer chains with very high molecular weight, while HDPE has a high strength to density ratio.
UHMW stands for Ultra High Molecular Weight Polyethylene. It is also denoted by UHMWPE. The term HDPE stands for High Density Polyethylene.
UHMW is ultra-high molecular weight polyethylene. It is a thermoplastic polymer. This polymer compound contains extremely long polymer chains and has a high molecular weight (about 5-9 million amu). As a result, UHMW has the highest molecular density. However, the appearance of this compound is indistinguishable from HDPE.
Properties of UHMW
►It is a tough material.
►Has high impact strength
►No odor and no taste
►High sliding ability
►It is highly non-adhesive
►The compound is non-toxic and safe
►It does not absorb water.
All polymer chains in UHMW are very long and they are aligned in the same direction. Each polymer chain is bonded to the other surrounding polymer chains by van der Waals forces. This makes the whole structure very strong.
UHMW is produced by the polymerization of the monomer ethylene. The ethylene polymerization forms the base polyethylene product. The structure of UHMW is very different from that of HDPE due to the production method. UHMW is produced in the presence of metallocene catalysts (HDPE is produced in the presence of Ziegler-Natta catalysts).
HDPE is High Density Polyethylene. It is a thermoplastic polymer material. Compared to other forms of polyethylene, this material has a high density. HDPE has a density of 0.95 g/cm 3. Due to the very low branching of the polymer chains in this material, the polymer chains are tightly packed. This makes HDPE relatively stiff and provides high impact resistance. HDPE can be processed at temperatures around 120°C without any harmful effects. This makes HDPE autoclavable.
Properties of HDPE
Important properties of HDPE include.
► relatively difficult to
►high impact resistance
►Opaque or translucent appearance
►High strength to density ratio
►Not absorbing or absorbing less liquid
HDPE is one of the most recyclable plastic materials. These properties define the applications of HDPE.
Applications of HDPE
Some important applications include the following.
►Used as a container for many liquid compounds (e.g. milk) and for storing chemicals (e.g. alcohol).
►Production of plastic shopping bags
►HDPE is also used for cutting boards
►UHMW and HDPE are made from ethylene monomers.
►Both are thermoplastic polymers.
►Both have an indistinguishable appearance.
|UHMW vs HDPE|
|UHMW is ultra-high molecular weight polyethylene.||HDPE is high density polyethylene.|
|UHMW has very long polymer chains.||HDPE has short polymer chains compared to UHMW.|
|Molecular Weight of Polymer Chains|
|The polymer chains of UHMW have very high molecular weights.||The polymer chains of HDPE have low molecular weights compared to UHMW.|
|UHMW is produced in the presence of metallocene catalyst.||HDPE is produced in the presence of Ziegler-Natta catalyst.|
|UHMW does not absorb water (zero absorption).||HDPE may absorb water slightly.|