STABILIZATION AND MODIFICATION OF POLYCAPROAMIDE - Photochemical Reactions in Heterochain Polymers - page 40

of X-ray diffraction analysis. PCA fibres, containing XLY-XLYI compounds, in the range of
considered temperatures have marked melting peak (endoeffect at 218-220 0 C) [134]. Clear
character of melting peak shows narrow distribution of crystal part of the polymer according
to the sizes of crystallites [135].
Investidations in isothermal conditions have been carried out in the air at the temperature
150-200 0 C. Data of kinetics of samples mass loss during warming up show, that initial
sample (Figure 1.17, curve I) detects the greatest mass loss: undyed sample loses about 20%
for 6 hours and the one dyed by XLY compound - 31%. Induction period takes place in dyed
samples, but it is absent in initial PCA. Similar effect was observed in the work [136] during
investigation of dyes effect on thermal ageing of modular polymer.
Hence, introduction of bis-aroilenbenzimidazole derivatives into PCA increases polymer
thermal stability at warming up in the air, moreover the greatest effect is displayed in
compounds containing Ar-O-Ar and Ar-CH 2 -Ar in a bridge group. On the basis of obtained
results on photo- and thermooxidative PCA destruction one may come to a conclusion that
compounds possess light- and thermoprotective action, being displayed in increasing photo-
and thermal stability of the products from PCA.

Figure 1.16. Thermograms of unstabilized (I, I 1 ) and stabilized compound XLY (2, 2 1 ), XLYI (3, 3 1 )

and (4, 4 1 ) of PCA-fibre in the air.