NUKLEONIKA 2005, 50(4):153-159
Grażyna Przybytniak1, Krzysztof Mirkowski1, Andrzej Rafalski1, Andrzej Nowicki1, Izabela Legocka2, Zbigniew Zimek1
1 Institute of Nuclear Chemistry and Technology, 16 Dorodna Str., 03-195 Warsaw, Poland
2 Industrial Chemistry Research Institute, 8 Rydygiera Str., 01-793 Warsaw, Poland
The influence of hindered amine light stabilizers (HALSs) on physical and mechanical properties of
irradiated and non-irradiated isotactic polypropylene (PP) was studied. The stabilizers under
investigation were: Tinuvin 765 (T765) and Tinuvin 622 (T622) – derivatives of 1,2,2,6,6-pentamethyl
piperidine and Chimassorb 944 (C944) – a derivative of 2,2,6,6-tetramethyl piperidine. It was found that
the stabilizers reduce the amount of peroxyl radicals in the amorphous phase of PP. The irradiation
with electron beam causes a drop of apparent viscosity both in the original and in the modified PP
however the effect is smaller in the presence of HALSs. Admixture of T622 and T765 stabilizers increases
the crystallization temperature of non-irradiated PP by about 8-10°C (measured by DSC) what results
from the facilitated formation of a large number small microcrystals. It was concluded that HALSs
initiate two opposite tendencies – chemical protection against damage initiated by free radicals and,
simultaneously, physical enhancement of sensitivity towards irradiation by the increase of
nucleation density. In the studied systems, the presence of maleic anhydride does not improve
compatibility between the polymeric matrix and HALSs.