Abstract
The effect of polymerization kinetics and resin viscosity on the electrical response of a single carbon nanotube yarn (CNTY) embedded in a vinyl ester resin (VER) during polymerization was investigated. To analyze the effect of the polymerization kinetics, the concentration of initiator (methyl ethyl ketone peroxide) was varied at three levels, 0.6, 0.9, and 1.2 wt.%. Styrene monomer was added to VER, to reduce the polymer viscosity and to determine its effect on the electrical response of the CNTY upon resin wetting and infiltration. Upon wetting and wicking of the CNTY by VER, a transient decrease in the CNTY electrical resistance (ca. −8%) was observed for all initiator concentrations. For longer times, this initial decrease in electrical resistance may become a monotonic decrease (up to ca. −17%) or change its trend, depending on the initiator concentration. A higher concentration of initiator showed faster and more negative electrical resistance changes, which correlate with faster gel times and higher build-up of residual stresses. An increase in styrene monomer concentration (reduced viscosity) resulted in an upward shift of the electrical resistance to less negative values. Several mechanisms, including wetting, wicking, infiltration, electronic transfer, and shrinkage, are attributed to the complex electrical response of the CNTY upon resin wetting and infiltration.
Highlights
Accepted: 28 February 2021The goal of carbon nanotube yarn (CNTY) production is to translate the excellent properties of individual carbon nanotubes (CNTs) to this continuous fiber assembly [1].Due to their hierarchical assembly, CNTYs possess outstanding electro-mechanical properties, which can be utilized for advanced sensory applications and mechanical reinforcement [2,3,4,5]
This study investigates the use of a CNTY as an in situ sensor for monitoring polymer curing, through the electrical response of a single CNTY embedded into a thermosetting resin (VER)
Styrene monomer, “FibreGlast #70 pure styrene thinner” (Brookville, OH, USA), was added to the neat vinyl ester resin (VER), to alter the polymer viscosity, in order to determine its effect on infiltration and the resulting electrical response of the CNTY
Summary
The goal of carbon nanotube yarn (CNTY) production is to translate the excellent properties of individual carbon nanotubes (CNTs) to this continuous fiber assembly [1]. Due to their hierarchical assembly, CNTYs possess outstanding electro-mechanical properties, which can be utilized for advanced sensory applications and mechanical reinforcement [2,3,4,5]. Regarding CNTYs dependence of electrical resistance with strain, the piezoresistive response of the yarn is driven by changes in its conductive network This is a function of contact points and tunneling due to CNT and CNT bundles/fibrils proximities [7,8]. The dependence of mechanical, thermal, and chemical enviroments on the electrical response of CNTYs, combined with their tailorable structure, flexibility, and high surface area, makes them excellent candidates for sensory applications [3,9,10,11]
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