The purpose of this project was to investigate commodity polymers. Two commercial polymers, high-density polyethylene (HDPE) and low-density polyethylene (LLDPE), as well as polystyrene (PS), synthesised by free radical polymerisation were investigated in terms of molecular characteristics, thermal properties and a clear difference between the polymers was noted. Additionally, the mechanical properties of HDPE and LLDPE were investigated and most interestingly, a difference in the tensile strength of HDPE and LLDPE was observed, even though they consist of the same monomer and just vary in their macromolecular architecture.