Alteration of matrix curing characteristics and its role in extension of hydrodynamic equation for predicting viscoelastic properties of nitrile rubber/silica nanocomposites

Abstract

Neglecting the alteration of matrix curing characteristics in a filled rubber nanocomposite, as a result of possible interactions between the nano filler and curing agent ingredients, leads to inaccurate properties prediction using conventional hydrodynamic equations. In the current work, we present a new empirical extended version of hydrodynamic equation and examine its capability in predicting the viscoelastic properties of NBR/nanosilica system in which the negative influence of the filler on the curing process of the NBR matrix was confirmed through various analyses such as tensile test, rheometry, swelling experiments, and dynamic mechanical analysis.The results showed that the proposed empirical extended model is able to account the contribution of alteration of matrix curing characteristics in changing the composite properties below the filler percolation threshold. It was demonstrated that the extended model provides more accurate prediction of viscoelastic properties of silicafilled cured NBR nanocomposites above glass transition temperature. KEYWORDS extension of hydrodynamic equation, nanocomposites, nitrile rubber (NBR), nanosilica, viscoelastic properties prediction 1 | INTRODUCTION Unfilled-gum rubbers usually have weak viscoelastic and mechanical properties as well as high swelling. Nano reinforcing fillers such as clay, carbon nanotubes, graphenic compounds, and silica can increase the strength, hardness, storage modulus, and tear strength and reduce swelling of rubbers. 1 The intrinsic properties of a thermoplastic matrix usually remain unchanged during development of a composite system. However, due to involvement curing process, the cured elastomers exhibit different properties compared with their unvulcanized elastomers. 2,3 For a rubber composite, the extent of curing degree besides depending on the concentration of curing agents, processing, and curing conditions depends on the filler intervention in the curing process of the matrix rubber. 4,5 There are a number of studies that have examined the interactions between filler and elastomer by evaluating viscoelastic, mechanical, physical, and thermal properties of the elastomeric composites. Usually, the changes in the properties of rubber arising from presence of filler are considered and compared with properties of the unfilled rubber.One of the most widely used filled-rubbers is acrylonitrile butadiene rubber (NBR)/silica composites. The major uses of these compounds are in the parts that are exposed to hydrocarbon fuels. The main property of these compounds is the resistance against swelling, which has a direct relationship with the curing of compounds. Interaction between silica and curing agent components may have strong destructive effect on the swelling properties and performance of NBR nanocomposites. On the other hand, silica is a cost-effective filler which has very good affinity with NBR. This leads to its facile uniform dispersion in the NBR matrix. No additional costly modification process or uses of compatibilizer are necessary...

Epoxidized natural rubber composites containing K0.15Cr0.02Ni0.83O nanoparticles: Curing characteristics, dynamic mechanical, mechanical, morphological, and dielectric properties

“…This result may be due to absorption of some components of the curing agent on nano-filler surfaces, that is, ZnO and MBT accelerators. 35 Higher filler loadings produce more heat, resulting in shorter cure times in the system. 36 This observation is also supported by the decreased cure time with KCNO loadings greater than 0.5 phr.…”