Micro-ZnO

Figure 12.12 SEM images of NR composites containing (a) unmodified micro ZnO, (b) surface modified micro ZnO, (c) nano ZnO (d) modified nano ZnO. [Reused with permission from J. Appl. Polym. ScL, 2011, 122, 249.]...

The investigators observed superior cure properties for the nano-ZnO filled NR compounds, compared with the micro-ZnO-filled samples. The mix containing 2 phr of nano-ZnO (prepared by the investigators by sol-gel process) N2... 

The filled composites containing 5 phr of nano-ZOS and 10-15 phr of SCC exhibited comparable tensile properties, tear strength and hardness as that of the microcomposite containing 5 phr of micro-ZnO and 30 phr of precipitated silica. These observations also support the findings that stearic acid-coated nano-ZnO (ZOS), nano-BIAT and SCC are better dispersed due to the small size of the particles as well as the higher specific surface area as already discussed in this chapter. 

Sahoo et al. reported the effect of nano-ZnO (70 nm size) on the cure and mechanical properties of CB filled NR/NBR blends.1.0 phr of nano-ZnO in the CB filled compounds showed comparable properties as that containing 5.0 phr of micro-ZnO. But maximum torque was lower due to low degree of dispersion of ZnO in CB filled system. But Wang et al. used nano-ZnO mas-terbatch to improve the dispersion and consequently 1.0 phr of nano-ZnO in the CB filled SBR compounds produced equivalent maximum torque as that containing 5.0 phr of micro-ZnO. Elongation at break and tensile strength... 

The aforesaid studies make it more evident that the dosage of ZnO in rubber compounds can be conveniently reduced to a lower dosage from 5 phr of micro form to even 1 phr of nano to obtain almost comparable or even better technological properties as obtained with 5 phr of micro-ZnO. This reduced dosage... 

Nano-ZnO is required only in smaller dosages like 1 phr to produce comparable/better technological properties of NR vulcanizates compared to micro-ZnO. This also is environmentally advantageous. 

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