Ultrasonic treatment of polycarbonate/carbon nanotubes composites

Abstract

A twin-screw extruder having an ultrasonic treatment zone in the barrel was used to prepare polycarbonate (PC)/multi-walled carbon nanotubes (MWNTs) composites. The effect of molecular weight of PC, carbon nanotubes (CNTs) concentration and ultrasonic amplitude on processing characteristics, electrical, morphological, rheological and mechanical properties of PC filled with 0.2-1.5 wt% CNTs was investigated. Ultrasonic treatment showed significant effects on improving the dispersion and distribution of CNTs especially in low molecular weight PC (LPC). The electrical and rheological percolation thresholds of low and high molecular weight PCs obtained by fitting the experimental data to classic percolation theory were significantly decreased after ultrasonic treatment. Specifically, the electrical percolation threshold of LPC/CNTs composites decreased from 0.176 vol% (0.30 wt%) for untreated samples to 0.088 vol% (0.15 wt%) for treated samples at an amplitude of 13 m. To the best of our knowledge, this obtained value is the lowest percolation threshold, so far, achieved in melt processed PC/CNTs composites. The mechanism for the decrease of rheological and electrical percolation thresholds after ultrasonic treatment was proposed. Also, some improvements in mechanical properties (including the Young's modulus and elongation at break) of PC/CNTs composites after ultrasonic treatment at an amplitude of 13 m were observed. The ultrasonic extrusion technology is shown to be a suitable method for manufacturing high quality products at lower CNTs concentration.

Electrically conductive polycarbonate/ethylene‐propylene copolymer/multi‐walled carbon nanotubes nanocomposites with improved mechanical properties

“…Figure shows the volume resistivity curve of PC/EPC (10%) blend as a function of MWCNT. The electrical resistivity and percolation threshold of PC/MWCNTs has been reported in previous studies . For the case of PC/MWCNTs nanocomposites, the percolation threshold was reported between 1% and 2% MWCNTs .…”

“…The electrical resistivity and percolation threshold of PC/MWCNTs has been reported in previous studies. [53][54][55][56][57][58] For the case of PC/MWCNTs nanocomposites, the percolation threshold was reported between 1% and 2% MWCNTs. 58 The results of the experiment showed that MWCNTs improved the electrical conductivity of the PC/EPC blends.…”

Effect of ultrasonic extrusion of star styrene‐butadiene rubber on properties of carbon black‐ and silica‐filled compounds and vulcanizates

“…Ultrasonic extrusion of polymers has been extensively studied by Isayev and his coworkers. It can be used for devulcanization of rubbers, decrosslinking of crosslinked thermoplastics, compatibilization of polymer blends, and improvement of filler dispersion in polymer composites . The properties of ultrasonically treated polymers are determined by their molecular structures.…”

“…It can be used for devulcanization of rubbers, [5][6][7] decrosslinking of crosslinked thermoplastics, 8 compatibilization of polymer blends, 9,10 and improvement of filler dispersion in polymer composites. [11][12][13][14] The properties of ultrasonically treated polymers are determined by their molecular structures. To better understand the mechanism about how ultrasonic treatment changes the molecular structures of polymers, it is essential to study the effect of ultrasonic treatment on pure polymers.…”

Desarrollo, caracterización y estudio de nuevos polímeros reforzados por dispersión de nanofases y nanofluidos

“…A elevadas frecuencias o gradiente de cizalla, todas las muestras tienden a converger a los valores del PMMA puro, independientemente de la nanofase añadida, ya que en esas condiciones el comportamiento predominante es el de la matriz del polímero. A valores bajos, sí que existe un incremento de la viscosidad al añadir las diferentes nanofases, especialmente en los nanocomposites procesados a baja SME, ya que en estos casos la movilidad de las cadenas sí que se puede ver fácilmente influenciada [537]. Con respecto al PMMA puro, el incremento máximo de la viscosidad que se produce es de un 26,5% para la nanofase híbrida GO-LI, del 48,6% para la nanofase pura GO y del 62,6% en el caso de la nanofase híbrida que contiene los nanotubos de carbono (GO-NT).…”