This document specifies two methods for evaluating the melting behaviour of semi-crystalline polymers. Melting temperatures determined by the different methods usually differ by several kelvins for the reasons explained in the introduction. Method A: Capillary tube This method is based on the changes in shape of the polymer. It is applicable to all semi-crystalline polymers and their compounds. NOTE 1 – Method A can also be useful for the evaluation of the softening of non-crystalline solids. Method B: Polarizing microscope This method is based on changes in the optical properties of the polymer. It is applicable to polymers containing a birefringent crystalline phase. It may not be suitable for plastics compounds containing pigments and/or other additives which could interfere with the birefringence of the polymeric crystalline zone. NOTE 2 – Another method applicable to semi-crystalline polymers is described in ISO 11357-3, Plastics – Differential scanning calorimetry (DSC) – Part 3: Determination of temperature and enthalpy of melting and crystallization.