EVALUATION OF THE HETEROGENEITY IN LINEAR LOW-DENSITY POLYETHYLENE COMONOMER UNIT DISTRIBUTION BY DIFFERENTIAL SCANNING CALORIMETRY CHARACTERIZATION OF THERMALLY TREATED SAMPLES

A new procedure for analysing the structure of linear low-density polyethylene (LLDPE) based on differential scanning calorimetry (d.s.c.) has been developed. LLDPE with heterogeneous and homogeneous distributions of comonomer units have been annealed in stages at decreasing temperatures starting from the melt. With this new procedure, it has been possible to show on d.s.c. thermograms the appearance of various families of macromolecules in the case of heterogeneous copolymers. In the case of more homogeneous copolymers, various families are still present in the material but in a smaller number. Furthermore, using the various melting peaks that appeared on the d.s.c. thermogram during the heating of the annealed polymer and with the help of a calibration curve, it has been possible to determine qualitatively the composition of the LLDPE.