The example of polyethylene of low density (PELD) crystallization in ethylbenzene and some other alkylbenzenes presence demonstrates
the unsufficiency of formal liquidus curve knowledge for the description of phase equilibrium in amorphous-crystalline polymer-liquid
system. Experimental data affirming polymorphous structure of PELD crystalline phase and influence of the solvent on the order
of various regular structures formation in it are being reported.
Investigated materials were produced from polyethylene
of low density (PE-LD) and a filler: carbon black or chalk. A part of the
samples was kept in ambient temperature over several months in order to study
the effect of material ageing. The qualitative conclusions were drawn based
on a precise analysis of shape of DSC curves and the basic investigations
of PE morphologies known from literature. The influence of the thermal history
and the filler contents on the amount and kind of crystal phase was established.
Additionally, the effect of the measurement technique, in our case it was
positron annihilation lifetime spectroscopy (PALS), on the morphological feature
changes was found. The paper serves selected examples of problems solved by
DSC. However, from the other hand, the authors discuss critically the opportunity
given by this method.