STABILIZATION AND MODIFICATION OF POLYCAPROAMIDE - Photochemical Reactions in Heterochain Polymers - page 41

Figure 1.17. Kinetic curves of mass loss of unstabilized (I) and stabilized compounds XLIII-(2), XLIY-
(3), XLY-(4), XYI-(5) of PCA-fibre in isothermal conditions at T=200 0 C.

It was shown earlier that (diphenylamine-p-tolylive-cyanate) urea (DTCU) may be used
as antioxidant of thermo- and photooxidative destruction of AC. It was interesting to use
DTCU for increasing antioxidative stability of PCA. With this purpose small amount of
DTCU were introduced into ε - caprolactam directly before its polycondensation, which was
carried out according to well known methods [132]. Content of DTCU additives in
polycondensation mixture was 0,5 - 3% from caprolactam mass.
Data on effect of DTCU concentration on viscosity characteristics and change of PCA
molecular mass before and after ultra - violet irradiation are given in Table 12.
Table 12. Dependence of viscosity characteristics of PCA on DTCU content before and
after ultra-violet irradiation

DTCU content in %
from PCA mass

Specific viscosity % of conservation, η

specific

Before irradiation After irradiation

0 0,68 0,54 80

0,5 0,66 0,62 94

1,0 0,62 0,60 97

2,0 0,76 0,70 82

3,0 0,56 0,52 93

As it seen from the Table DTCU additives (0,5-2% from the mass of ε-caprolactam) do
not exercise influence on polymer viscosity characteristics and, hence, on its molecular mass.
If one may consider that during PCA photooxidation the rate of formation of joints
between polymer molecules is much lower than during photolysis in vacuum [4], then little
change of specific viscosity of irradiated PCA, containing DTCU 0,5-2% from polymer mass,