It has a relatively high density among polyethylenes, typically in the range of 0.941 - 0.965 g/cm³. The molecular chains of HDPE are more closely packed and have a linear structure with fewer branches. The average molecular weight of HDPE is lower than that of UPE. For example, the molecular weight of HDPE usually ranges from 100,000 to 300,000 g/mol.
UPE:
As the name implies, it has an ultra - high molecular weight. The molecular weight of UPE can be as high as several million g/mol (usually in the range of 3 - 6 million g/mol). The molecular chains are very long and have a high degree of entanglement, which gives it unique physical properties.