Effect of Curing Temperature of Epoxy Matrix on the Electrical Response of Carbon Nanotube Yarn Monofilament Composites

Omar Rodriguez-Uicab,Tannaz Tayyarian,Jandro L Abot

doi:10.3390/jcs6020043

Omar Rodriguez-Uicab, Tannaz Tayyarian + Show 1 more

Open Access

https://doi.org/10.3390/jcs6020043

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Abstract

In order to evaluate the capability of carbon nanotube yarn (CNTY)-based composites for self-sensing of temperature, the temperature-dependent electrical resistance of CNTY monofilament composites was investigated using two epoxy resins: one that cures at 130 °C (CNTY/ERHT) and one that cures at room temperature (CNTY/ERRT). The effect of the curing kinetics of these epoxy resins on the electrical response of the embedded CNTY was investigated in prior studies. It was observed that the viscosity and curing kinetics affect the level of wetting and resin infiltration, which govern the electrical response of the embedded CNTY. In this work, the cyclic thermoresistive characterization of CNTY monofilament composites was conducted under heating–cooling, incremental heating–cooling, and incremental dwell cycles in order to study the effect of the curing temperature of the epoxy matrix on the electrical response of the CNTY monofilament composites. Both monofilament composites showed nearly linear and negative temperature coefficients of resistance (TCR) of −7.07 × 10−4 °C−1 for specimens cured at a high temperature and −5.93 × 10−4 °C−1 for specimens cured at room temperature. The hysteresis loops upon heating–cooling cycles were slightly smaller for high-temperature cured specimens in comparison to those cured at room temperature. A combination of factors, such as resin infiltration, curing mechanisms, intrinsic thermoresistivity of CNTY, variations in tunneling and contact resistance between the nanotubes and CNT bundles, and the polymer structure, are paramount factors in the thermoresistive sensitivity of the CNTY monofilament composites.

Highlights

The excellent mechanical, electrical, and thermal properties of carbon nanotubes (CNTs) are leading to an increase in their applications in composite materials with sensing and actuating capabilities [1,2], structural health monitoring [3,4] and electrical devices [5,6]
The carbon nanotube yarn (CNTY) used in this study was fabricated from a vertically aligned carbon nanotube (CNT) array with no post-processing at Nanoworld Laboratories (University of Cincinnati, Cincinnati, OH, USA)
Each specimen was subjected to heating above room temperature (RT~25 ◦C), which was ramped up at 0.8 ◦C/min until 80 ◦C (40 min), and cooling back to RT at 0.2 ◦C/min (4 h) for four continuous cycles

Summary

Introduction

The excellent mechanical, electrical, and thermal properties of carbon nanotubes (CNTs) are leading to an increase in their applications in composite materials with sensing and actuating capabilities [1,2], structural health monitoring [3,4] and electrical devices [5,6]. Lascano et al [21] investigated the effect of the curing temperature on the density, rheological, morphological, mechanical, and thermomechanical properties of epoxy resins Their results showed higher density and mechanical properties in polymers cured at medium temperatures in comparison to polymers cured at lower temperatures. The intrinsic thermoresistivity of CNTYs and the resin infiltration of the CNTY and the resin crosslinking are used to explain the analyzed thermoresistive response

Materials

Results

Swelling Behavior of Epoxy Resin Matrix

Scanning Electron Microscopy