Effect of zinc oxide nanoparticles as cure activator on the properties of natural rubber and nitrile rubber

Abstract

Zinc oxide (ZnO) nanoparticles were synthesized by homogeneous precipitation and calcination method and were then characterized by transmission electron microscopy and X-ray diffraction analysis. Synthesized ZnO was found to have no impurity and had a dimension ranging from 30-70 nm with an average of 50 nm. The effect of these ZnO nanoparticles as cure activator was studied for the first time in natural rubber (NR) and nitrile rubber (NBR) and compared with conventional rubber grade ZnO with special reference to mechanical and dynamic mechanical properties. From the rheograph, the maximum torque value was found to increase for both NR and NBR compounds containing ZnO nanoparticles. ZnO nanoparticles were found to be more uniformly dispersed in the rubber matrix in comparison with the conventional rubber grade ZnO as evident from scanning electron microscopy/X-ray dot mapping analysis. The tensile strength was observed to improve by 80% for NR when ZnO nanoparticles were used as cure activator instead of conventional rubber grade ZnO. An improvement of 70% was observed in the case of NBR. The glass transition temperature (T g ) showed a positive shift by 68C for both NR and NBR nanocomposites, which indicated an increase in crosslinking density. The swelling ratio was found to decrease in the case of both NR and NBR, and volume fraction of rubber in swollen gel was observed to increase, which supported the improvement in mechanical and dynamic mechanical properties.

Synthesis and effect of surface modified nano ZnO in natural rubber vulcanization

“…2(b-d)]. The SEM images of NZ 5 and NZ 7 [ Fig. 2(b,c)] show only very few agglomerates, which are micro particles of CBS.…”

“…Tensile strength increased with increase in dosage of ZOBS up to 7 phr in the mix NZ 5 (Table III). This was due to increase in the number of sulfidic crosslinks by the enhanced synergic action between BIAT caps on zinc oxide surface and the CBS particles diffusing on to ZnO.…”

“…The synergic action between BIAT caps on zinc oxide surface and the CBS particles diffusing on to ZnO could increase the crosslink density as the concentration of BIAT, stearic acid, and zinc ion increased in ZOBS (which is maximum in 7 g of ZOBS). This has imparted maximum tensile strength to NZ 5 .…”

“…Therefore, to enhance the reactivity of ZnO, the availability of Zn þ2 must be increased. 5 The extra time and energy required by the accelerator and fatty acid particles to diffuse through the visco-elastic polymer matrix leading to the adsorption of these particles on to the surface of ZnO particles can be saved by capping [6][7][8] of ZnO during its sol-gel precipitation. [9][10][11][12][13] It is well known that due to large surface area/mass available for nano ZnO, it is more advantageous to use it in sulfur vulcanization of rubber.…”

Synthesis of Zn/Mg oxide nanoparticles and its influence on sulfur vulcanization

“…This effect can be partly attributed to the small particle size of the Zn 1Àx Mg x O particles. Bhowmick and coworkers 4,5 found that ZnO nanoparticles (30-70 nm) increased the crosslink degree by 15% compared with standard ZnO. On the other hand, the fact that, even with bigger sizes, higher amounts of crosslinked products are formed suggests that Zn 1Àx Mg x O nanoparticles are more active and more effective transporting sulfur into the hydrocarbon chain than ZnO nanoparticles.…”