Both are types of plastics but they vary by density and structure.HDPE (high density polyethene) is made of many linear chains which are held together by intermolecular forces.LDPE (low density polyethene) is made of branched chains, which are also held by intermolecular forces. Due to its branched nature, there are more gaps between the individual chains and overall there are less intermolecular forces. This means that LDPE is both less dense and less strong than HDPE.