Blend Structure and n-Type Thermoelectric Performance of PA6/SAN and PA6/PMMA Blends Filled with Singlewalled Carbon Nanotubes

Abstract

The present study investigates how the formation of melt-mixed immiscible blends based on PA6/SAN and PA6/PMMA filled with single walled nanotubes (SWCNTs) affects the thermoelectric (TE) properties. In addition to the detailed investigation of the blend morphology with compositions between 100/0 wt.% and 50/50 wt.%, the thermoelectric properties are investigated on blends with different SWCNT concentrations (0.25–3.0 wt.%). Both PA6 and the blend composites with the used type of SWCNTs showed negative Seebeck coefficients. It was shown that the PA6 matrix polymer, in which the SWCNTs are localized, mainly influenced the thermoelectric properties of blends with high SWCNT contents. By varying the blend composition, an increase in the absolute Seebeck coefficient, power factor (PF), and figure of merit (ZT) was achieved compared to the PA6 composite which is mainly related to the selective localization and enrichment of SWCNTs in the PA6 matrix at constant SWCNT loading. The maximum PFs achieved were 0.22 µW/m·K2 for PA6/SAN/SWCNT 70/30/3 wt.% and 0.13 µW/m·K2 for PA6/PMMA/SWCNT 60/40/3 wt.% compared to 0.09 µW/m·K2 for PA6/3 wt.% SWCNT which represent increases to 244% and 144%, respectively. At higher PMMA or SAN concentration, the change from matrix-droplet to a co-continuous morphology started, which, despite higher SWCNT enrichment in the PA6 matrix, disturbed the electrical conductivity, resulting in reduced PFs with still increasing Seebeck coefficients. At SWCNT contents between 0.5 and 3 wt.% the increase in the absolute Seebeck coefficient was compensated by lower electrical conductivity resulting in lower PF and ZT as compared to the PA6 composites.

Polyethylene Glycol as Additive to Achieve N-Conductive Melt-Mixed Polymer/Carbon Nanotube Composites for Thermoelectric Application

“…The light microscopic images of the composites show many large elongated remaining SWCNT agglomerates ( Figure 5 and Figure 10 ). This poor dispersibility of the SWCNT Tuball™ material has been reported before and was found to also be typical in PP [ 15 , 31 ], acrylonitrile butadiene styrene (ABS) [ 32 ], and polyamide 6 [ 32 , 33 ]-based composites. From the SEM study, it was concluded that PC and PEG are miscible in the solid state, in which the measurements were performed, but PBT and PEEK are not.…”

Review of Thermoelectric Generators at Low Operating Temperatures: Working Principles and Materials

“…In addition, the potential candidates for low-operating-temperature TE materials are only laboratory technologies at present, and large-scale, low-cost preparation technologies need to be explored further. Very recently, research on graphene, single-walled carbon nanotubes (SWCNTs), and TE material nanocomposites demonstrated better ZT performance, as well as improved electrical conductivity (σ) and were successful in suppressing the thermal conductivity, κ [ 27 , 165 , 166 , 167 ]. The κ of TE nanocomposites is predicted to be lower than that of their bulk equivalents of the same chemical configuration.…”

“…Very recently, research on graphene, single-walled carbon nanotubes (SWCNTs), and TE material nanocomposites demonstrated better ZT performance, as well as improved electrical conductivity (σ) and were successful in suppressing the thermal conductivity, κ [ 27 , 165 , 166 , 167 ]. The κ of TE nanocomposites is predicted to be lower than that of their bulk equivalents of the same chemical configuration.…”

High Thermoelectric Power Generation by SWCNT/PPy Core Shell Nanocomposites

“…These conducting polymers exhibit light weight, lower cost, reasonable thermal conductivity, easy fabrication process, and excellent flexibility. For instance, the thermoelectric performance of organic polymers can be significantly improved by controlling the combination of carbon nanotubes (CNTs) or graphene nanosheets with such polymers [ 1 , 2 , 3 ]. So far, the most common conducting polymers that have been investigated as thermoelectric materials are polyaniline (PANI) [ 4 ], polypyrrole (PPy) [ 5 ], and poly (3,4-ethylene dioxythiophene) (PEDOT) [ 6 , 7 , 8 ].…”