Extrapolation of the Orthorhombic n-Paraffin Melting Properties to Very Long Chain Lengths

An analysis of the equation TM=T0 (n+a) / (n+b) is made in order to determine the convergence temperature T0 of the melting temperatures of the n-paraffins from C44 to C100. A good fit is obtained using T0=414.3°K, a=—1.5, and b=5.0. This value of T0 (414.3°K=141.1°C) has an estimated total uncertainty of ±2.4°K and is proposed as the correct value of the equilibrium melting temperature of polyethylene. It is shown that presently available data do not permit accurate extrapolation of the n-paraffin heats and entropies of fusion to the polymer limit.