STABILIZATION AND MODIFICATION OF POLYETHYLENETEREPHTHALATE - Photochemical Reactions in Heterochain Polymers - page 134

On the thermogram of unmodified PETP, Figure 3.11 (curve 1) temperature range of
melting is not sharp transition by itself, but the region of extended range. This points to the
presence, together with absolute order, of metastable crystalline forms extending temperature
range of melting. Initial PETP and modified by hexaazocyclones have clearly defined peaks
of melting (endoeffect at 250-269 ºC).
Clear character of melting peaks points to narrow distribution of polymer crystalline part
according to crystals sizes [298]. However, endoeffect at 269 ºC (initial PETP - fibre), not
accompanied by mass loss and corresponding to the melting of crystalline regions, in
modified PETP - fibres, containing additives of hexaazocyclanes HC-1 - HC-7, is shifted
into the region of lower temperatures (250-263 ºC).
According to Bell and Damblton [299] PETP may have two morphological forms of
crystals which define double endothermic effect in melting region. Folded structure was
assigned to form I, which initial more high temperature endotherm corresponds to, and for the
form II, responsible for more low temperature endotherm, was suggested crystalline structure
from more extended chains.
Figure 3.12. View of DTA curves for PETP - fibres modified by HC-3 (4) and HC-4 (5).