Experimental
Materials and sample preparation
One LDPE resin and five LLDPE resins were used in
the blend systems studied. The LLDPE resins were
produced using conventional Ziegler–Natta catalysts.
The characteristics of the resins are given in Table 1.
The density and the melt flow index (MFI) of each
resin were determined in accordance with ASTM
method D-1505 and ASTM method D-1238 (Condition
E), respectively. A mass of 2.16 kg was used in the
determination of the MFI values. Blends of LLDPE1
through LLDPE5 with LDPE were prepared by melt
mixing the polymers in a Brabender Plasticorder mixer
at a temperature of 160°C for 5 min using a mixing
speed of 60 rpm.
Plaques (400 μm thickness) of the blends were
prepared by compression moulding at 180°C and
150 MPa and were immediately quench-cooled by
immersion in cold water. Samples (ca. 5 mg) were
punched from the plaques and sealed in aluminium
pans in preparation for heat treatment and/or thermal
analysis. Prior to the determination of its crystalline
melting temperature, each sample was annealed