THE EFFECT OF FILLER TYPE AND RADITATION DOSE ON THE MECHANICAL PROPERTIES OF HNBR COMPOSITES PREPARED BY THERMAL AND THERMO-RADIATION VULCANIZATION

In this work, elastomeric composites based on hydrogenated nitrile butadiene rubber (HNBR) were obtained using both thermal and thermo-radiation vulcanization in the presence of two different fillers: clay and carbon black.

The main component is HNBR 3606. An elastomer mixture was obtained on laboratory rollers in sheet form with thickness of 2 mm. The thermal vulcanization process was carried out at 150 °C for 20 minutes. Radiation-thermal vulcanizates were obtained by preheating in an electric press at 150 °C for 5 minutes and in next step samples were exposed to 100, 200, 300 and 400 kGy doses of ionizing radiation. The goal was to estimate the effectiveness of the reinforcement of each filler under various conditions of vulcanization and determine the optimal dose of radiation to achieve maximum mechanical strength.

Experimental results showed that HNBR vulcanizates with carbon black consistently demonstrated higher tensile strength than samples with clay. This is explained by the strong interaction of carbon black particles with the elastomeric matrix, which contributes to the formation of a more homogeneous and densely crosslinked network. In contrast, samples filled with clay showed weaker interfacial bonding and lower stress transfer efficiency, leading to decrease in mechanical performances.

With an increase in the dose of radiation, the tensile strength of all samples increased, reaching a maximum at 300 kGy (optimal dose) due to an increase in the crosslinking density and the formation of a network structure. However, at a dose of 400 kGy, a slight decrease in strength was observed, probably caused by excessive chain scission and molecular degradation. Elongation at break showed the opposite trend, decreasing with the increase in radiation dose, which confirms the progressive strengthening of the network.