The influence of multi-walled carbon nanotubes (MWCNTs) on thermal, mechanical and wetting properties as well as rheological behavior of poly(ethylene-co-vinyl acetate) (EVA)/acrylonitrile-butadiene rubber nanocomposites were studied. The solid surface free energy (γ s ), work of adhesion (W A ), interfacial free energy (γ sl ), spreading coefficient (S c ) and Girifalco-Good's interaction parameter (ϕ) were calculated for the materials fabricated.The results showed that the contact angle and γ sl decreased; however, γ s , W A , S c , and ϕ increased with the increase in MWCNTs content. The maximum tensile strength and toughness were obtained for the nanocomposite containing 1 wt% nanofillers. It was also found that both of the relaxation ratio (Rr) and relaxation rate index (n) decreased with increasing in the carbon nanotubes (CNTs) concentration. The results designated that the values of Rr and n for the nanocomposite containing 7 wt% MWCNTs were 19% and 60% smaller than those of the unfilled blend, respectively. The Casson plot analysis indicated that the yield stress of the molten materials incremented with the increase in MWCNTs loading according to a quadratic equation. The analysis of crystallization exotherms and melting endotherms revealed that CNTs triggered the crystallization process at slightly higher temperature, however, melting point slightly and the rate of nucleation noticeably reduced with the increase in the nanofillers content.

In this work, the effect of multi‐walled carbon nanotubes (MWCNTs) on electrical conductivity and rheological behavior of poly(ethylene‐co‐vinyl acetate) (EVA)/acrylonitrile‐butadiene rubber (NBR) blends containing 0 to 7 wt% MWCNTs are investigated. The theoretical calculations according to the interfacial free energy of the components revealed that the nanofillers had a tendency to locate in NBR domains. However, the rheological, electrical, and morphological studies indicated that the majority of the MWCNTs remained in the EVA phase. Shear creep measurements of the molten materials showed that the creep stability improved steadily with the increase in MWCNTs content. The creep behaviors of the materials, except EVA, were analogous to the Burgers model prediction and all four parameters of the model increased in value with the increase in the nanofillers content in comparison with those of the unfilled blend. The rheological studies indicated that the damping factor (tanδ) for the materials containing small amounts of the nanofillers reached a maximum and subsequently decreased with rising temperature. However, for the materials having 1 wt% MWCNTs and higher, the tanδ values were smaller at the highest temperature (200°C) than those of the lowest temperature (100°C) investigated in this work. The electrical percolation threshold was also found to take place at about 2.80 wt% MWCNTs loading.

Rheological percolation, gel-like behavior and electrical properties of multi-walled carbon nanotubes (MWCNTs) filled ethylene-co-vinyl acetate/acrylonitrile-butadiene copolymer blends containing 0-7 wt% MWCNTs were studied. The Winter-Chambon criterion validity was evaluated for gelation of the system. The rheological and electrical percolation threshold, gel point (Pg), relaxation exponent (n), gel strength (Sg) and the fractal dimension (df) at the gel point were calculated. The formation of physical gel and rheological percolation threshold were both found to occur at 1 wt% MWCNTs concentration. Based on the df value determined, it was revealed that the system behaved similar to the one in which the excluded volume interactions were nearly screened. It was also found that the storage modulus (G') near the Pg followed a power law scaling relationship in the form G'=8257ε1.36 where ε=|P-Pg|/Pg is the distance from Pg. The electrical conductivity of the nanocomposites increased with the increase in MWCNTs loading after the nanofillers content surpassed a certain value. A schematic model was proposed to demonstrate electrical conduction with the increase in MWCNTs concentration. The excluded volume and hard core models were also employed to estimate the average aspect ratio of the nanofillers embedded in the system.