Abstract
Melt processing is considered one of the favored techniques to produce polymer nanocomposites with various inorganic fillers such as graphene and carbon nanotubes (CNTs). Due to their superior conductivity and tensile properties, among others, CNTs have been applied in broad applications. When a low filler fraction is desired, a high degree of dispersion is required in order to benefit from the intrinsic properties of CNTs. However, due to their high cohesive energy, dispersing CNTs in polymer melts is a difficult task. This study employed the melt mixing technique with a controlled residence time of 20 min to disperse single-walled carbon nanotubes (SWNTs) into a polypropylene matrix. The composites were prepared by using a corotating twin-screw extruder equipped with a back-conveying element with varying amounts of SWNTs from 0.29 to 6.56 wt.%. Mechanical, electrical, morphological, and rheological properties were evaluated. Due to the filler effect, storage, loss modulus, and complex viscosity increased with the SWNT content. Based on the van Gurp–Palmen plot, 0.29 wt.% SWNTs was the rheological percolation threshold, and the electrical property measurement revealed a 1.4 wt.% SWNT electrical percolation threshold based on the statistical percolation theory. Relatively large agglomerates were found when the SWNT content increased more than 1.28 wt.%.
Highlights
The development of new functional polymer materials is often accomplished by several strategies, such as the mixing of a conventional matrix polymer with other polymer components and/or solid fillers
Particle analysis using the incorporated software developed by KYENCE was performed in order to quantify the area fraction AA of undispersed primary single-walled carbon nanotubes (SWNTs) agglomerates according to Equation (3) [1]
As the SWNT content increases in this composite system, the SME increases, possibly due to the dominance of nanotube–nanotube interactions, which may affect the dispersion of SWNTs in the composites
Summary
The development of new functional polymer materials is often accomplished by several strategies, such as the mixing of a conventional matrix polymer with other polymer components (polymer blends) and/or solid fillers (composites). Following their first detailed description in the scientific literature in 1991, these “coaxial tubes of graphitic sheets” [2] attracted the attention of the wider scientific community and found practical application due to their outstanding performance, especially their electrical [3,4,5,6,7,8], thermal [9,10,11,12], and mechanical properties [12,13,14,15,16,17,18,19]. Requires well-dispersed CNT masterbatches, which should be generated from the masterbatch production step When it comes to the melt mixing process of masterbatches, processing conditions need to be considered, namely rotation speed, residence time, and temperature profile. To evaluate the dispersion state of SWNTs, rheological, morphological, electrical, and mechanical properties were measured
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