Mechanical, Electrical and Rheological Behavior of Ethylene-Vinyl Acetate/Multi-Walled Carbon Nanotube Composites

Abstract

This paper investigates the rheological, mechanical and electrical properties of a Ethylene-Vinyl Acetate (EVA) polymer filled with 1, 3 and 5 wt.% multi-walled carbon nanotubes (MWCNTs). The melt flow and pressure-volume-Temperature (pvT) behaviors of the EVA/MWCNT composites were investigated using a high-pressure capillary rheometer, while the electro-mechanical response was investigated on injection-molded samples. Rheological experiments showed that the melt shear viscosity of the EVA/MWCNT composite is dependent on nanotube loading and, at high shear rates, the viscosity showed temperature-dependent shear thinning behavior with a flow index n < 0.35. The specific volume of the EVA/MWCNT composite decreased with increasing pressure and MWCNT wt.%. The transition temperature, corresponding to the pvT crystallization, increased linearly with increasing pressure, i.e., about 20 to 30 °C when cooling under pressure. The elastic modulus, tensile strength and stress at break increased with increasing MWCNT wt.%, whereas the strain at break decreased, suggesting the formation of MWCNT secondary agglomerates. The electrical conductivity of the EVA/MWCNT composite increased with increasing MWCNT wt.% and melt temperature, reaching ~10−2 S/m for the composite containing 5 wt.% MWCNTs. Using the statistical percolation theory, the percolation threshold was estimated at 0.9 wt.% and the critical exponent at 4.95.

Experimental Investigation of the Melt Shear Viscosity, Specific Volume and Thermal Conductivity of Low-Density Polyethylene/Multi-Walled Carbon Nanotube Composites Using Capillary Flow

“…Owing to their electrical, thermal, mechanical and chemical properties, complemented by a high surface area [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ], carbon nanotubes (CNTs) are ideal fillers for a multitude of applications, particularly for structural aerospace, defense and automotive components [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]; conducting components in the field of electronics; sensors and biosensors [ 2 , 3 , 4 , 5 , 6 , 9 , 10 , 11 , 12 , 13 , 15 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]; and coatings and paints [ 33 ].…”

“…Melt viscosity is one of the most important thermo-physical properties for the polymer processing industry as it is required for product development, tooling design, process optimization, quality control and troubleshooting [ 34 , 35 , 36 , 37 , 38 ]. Specifically, for polymer/CNT composites, melt rheology can be used to assess, in a systematic way, the state of CNTs in polymers (e.g., dispersion, agglomeration and adhesion) after melt processing, which links to the mechanical and electrical properties of the final products [ 1 , 3 , 5 , 9 , 10 , 11 , 13 , 15 , 18 , 21 , 22 , 24 , 25 , 39 ]. Moreover, melt rheology is an important tool for understanding how CNTs affect the processing behavior of polymer/CNT composites [ 3 , 5 , 11 , 14 , 15 , 18 , 39 , 40 , 41 ].…”

“…Although considerable research has been conducted regarding the material properties of polymer/CNT composites, including mechanical, thermal and electrical properties, only a few investigations have focused on the high shear rate rheological behavior [ 10 , 11 , 13 , 15 , 18 , 25 , 39 , 40 , 41 , 42 , 43 ]. Usually, the rheological properties have been measured by parallel plates or con-plates using dynamic oscillation frequency sweeps under linear viscoelastic conditions and shear rates in the range of 0.01 to 100 s −1 [ 1 , 9 , 14 , 19 , 21 , 22 , 24 , 26 , 44 ].…”

“…Usually, the rheological properties have been measured by parallel plates or con-plates using dynamic oscillation frequency sweeps under linear viscoelastic conditions and shear rates in the range of 0.01 to 100 s −1 [ 1 , 9 , 14 , 19 , 21 , 22 , 24 , 26 , 44 ]. However, in practice, polymer/CNT composites are processed at higher shear rates, such as 10 3 –10 4 s −1 for injection molding [ 3 , 5 , 15 , 18 , 36 ].…”

Comparing Multi-Walled Carbon Nanotubes and Halloysite Nanotubes as Reinforcements in EVA Nanocomposites

“…Moreover, the addition of HNTs to EVA could enhance water resistance and oxygen permeability [ 40 ]. Various CNTs containing EVA-based nanocomposites had also been reported [ 41 , 42 , 43 , 44 , 45 ]. The mass production of high quality CNTs at lower cost and their exceptional electrical, thermal, and mechanical properties, make it one of the most attractive nanofillers.…”