Precise role of zirconia to boost up the mechanical, thermal, viscoelastic, dielectric, and chemical resistance properties of natural rubber-nitrile rubber blend

Silica and other metal oxides have been emerged as potential substitutes of conventional carbon black (CB) to reinforce elastomeric materials. It not only steers clear of the ill-effects of CB such as issues like carcinogenicity and carbon footprint but they can impart rich thermal, optical, dielectric, and antimicrobial properties to the composites in addition to appreciable reinforcement. Silica is of special mention in this context while titania and zirconia to follow next. In this work, we report efficacy of zirconia towards property enhancement of a rubber blend comprised of non-polar natural rubber (NR) and polar nitrile rubber (NBR). Designed and controlled incorporation of zirconia in rubber matrix via an in-situ approach offers appreciable reinforcement to the composites. This is due to the fine dispersion of zirconia in elastomer matrix (SEM), efficient rubber-filler interaction (DMA) and increased crosslinking densities (swelling study). Analysis by atomic force microscopy (AFM) and differential scanning calorimetry (DSC) indicates that in-situ zirconia acts in favour of improved blend compatibility as well. All these factors offer notable impact on the other composite properties viz. improved thermal stability, enhanced flame retardancy and excellent chemical resistance to the blend composites. Additionally, dielectric properties become better upon incorporation of in-situ zirconia. The enhancement of composite properties becomes more prominent upon surface modification of in-situ zirconia by an organosilane Bis-(3-triethoxysilylpropyl) tetrasulfide (TESPT). Superiority of in-situ zirconia over externally filled zirconia has been established by a comparative analysis. Hence, current study offers valuable insights on the potential of in-situ zirconia as a substitute of CB to reinforce the rubber blends. The findings have important implications for the development of high performance elastomeric composites that can sustain in harsh service conditions.