Which of the following is not suitable for the polymerisation of ethene to form high-density polythene?

Temperature of 500K

High density polymer (HDP) is formed when polymerisation of C₂H₄ takes place through addition in a hydrocarbon solvent with Ziegler-Natta catalyst at temperature of 333-343K and under a pressure of 6-7 atmospheres. Temperatures and pressure higher than this will favour the formation of LDP.