The effect of ionizing radiation on the mechanical properties of NBR elastomers reinforced by lignin


ŞEN M., AKSÜT D., KARAAĞAÇ B.

RADIATION PHYSICS AND CHEMISTRY, cilt.168, 2020 (SCI İndekslerine Giren Dergi) identifier identifier

Özet

This work aimed to identify the effects of ionizing radiation on the mechanical stability of acrylonitrile-butadiene rubber (NBR) elastomers reinforced and stabilized by lignin. To achieve this goal, NBR and NBR-Lignin elastomers were irradiated with gamma rays up to 80 kGy, in air atmosphere and at room temperature. The dose rate was 22 Gy/h. It has been observed that gamma irradiation had a significant effect on tensile properties of 0.5 phr lignin-containing NBR elastomer. Another important finding was that gamma irradiation had no significant effect on the tensile strength when the lignin concentration in NBR is over 1 phr whereas 0.5 phr lignin incorporation led a 17% increase in tensile strength after 80 kGy irradiation. On the other hand, elongation of break values of all the compounds were decreased with increasing absorbed dose. When the absorbed dose was reached to 80 kGy, decrease in the elongation at break was 11% for 0.5 phr and 19% for 1 phr lignin containing systems. This decrease was also attributed the additional cross-linking reactions during irradiation although some of the cross-links were previously inhibited by lignin during vulcanization. Cross-link density measurements and mechanical properties of the samples were evaluated together and it was concluded that the dominant effect of radiation on NBR elastomers is further cross-linking reactions. On the other hand, this effect could be inhibited by incorporating limited amount of lignin (up to 1 phr) in the compound. The prominent mechanism of lignin was explained most probably as scavenging free radicals and diminishing radical-radical combination in NBR chains. Finally, lignin is concluded to have a protective effect on mechanical properties of NBR elastomers against irradiation. 1 phr lignin can be used as an anti-rad for radiation exposed NBR elastomers to keep original mechanical properties as almost the same.