Natural Rubber/Carbon Nanotube Nanocomposites Prepared by Ultrasonically Aided Extrusion

Abstract

Natural rubber/multiwalled carbon nanotube (MWCNT) nanocomposites at loadings from 2 to 25 phr were prepared by ultrasonically aided extrusion at ultrasonic amplitudes up to 7.5 μm. Die pressure significantly decreased with an increase of ultrasonic amplitude, especially at higher loadings. Power consumption increased with ultrasonic amplitude and was almost insensitive to loadings until an amplitude of 5.0 μm. However, lower values of power consumption were observed at an amplitude of 7.5 μm for loadings of 10 and 15 phr. At these loadings, complex viscosity, storage, and loss moduli of compounds and vulcanizates were unaffected by ultrasonic treatment, whereas at other loadings, these properties were reduced with ultrasonic amplitude, indicating chain scission. Bound rubber in compounds decreased with treatment. The induction time during vulcanization was unaffected by ultrasonic treatment but decreased with loading, with the largest decrease observed at the lowest loading. The maximum torque in curing, cross-link density, and gel fraction of vulcanizates at loadings of 2, 3.5, 5, 7.5, and 25 phr decreased with ultrasonic amplitude, with the largest decrease observed at loading of 25 phr at an amplitude of 7.5 μm. The modulus at 100% and 300% and tensile strength of vulcanizates at loadings up to 15 phr were unaffected by the ultrasonic treatment, but these properties significantly decreased at a loading of 25 phr at an amplitude of 7.5 μm. Atomic force microscope studies of vulcanizates at a loading of 3.5 phr showed a deagglomeration at an amplitude of 7.5 μm, although dispersion analysis from an optical microscope at loadings of 3.5 and 7.5 phr did not show an improvement of dispersion by ultrasonic treatment. Optical microscope and AFM studies of vulcanizates at a loading of 25 phr indicated that ultrasonic treatment at an amplitude of 7.5 μm significantly improved dispersion of MWCNT. Such a behavior led to a strong Payne effect and an increase in hardness of vulcanizates.

Comparison of Reinforcing Efficiency of Carbon Black, Conductive Carbon Black, and Carbon Nanotube in Natural Rubber

“…During the past decade, CNT has been used as a filler in plastics to improve mechanical, electrical, and thermal properties. Currently, many attempts have also been made to study the possible use of CNT to improve certain properties of various rubbers, for example, styrene butadiene rubber (SBR), nitrile rubber, hydrogenated nitrile rubber, hydrogenated carboxylic nitrile rubber, ethylene propylene diene monomer, chloroprene rubber, silicone rubber (Q), natural rubber (NR), and rubber blends . Surprisingly, little attention is given to the comparison of reinforcing efficiency between CNT and conductive carbon black.…”

Hybrid Nanocarbons Reinforced Rubber Nanocomposites: Detailed insights about Mechanical, Dynamical Mechanical Properties, Payne and Mullin Effects

“…NR/SWNTs (2.0 phr) in relation to pure NR containing SWCNTs showed tensile strength and modulus higher by 56% and 63% respectively. The modulus at 100% and 300% and tensile strength of vulcanizates at loadings up to 15 phr were unaffected by sample prepared by the ultrasonic method [31]. Kueseng and Jacob [33] also studied mechanical properties of single-walled carbon nanotubes (SWCNT) filled NR nanocomposites prepared by solvent method.…”

Innovative Method of Devulcanizing Waste Rubber from the Automotive Industry

“…In the pursuit of recycling and repurposing vulcanized rubbers, it becomes paramount to identify a secure method for their devulcanization, involving the cleaving of their crosslink bonds. Rubber devulcanization is a transformative process wherein vulcanized waste rubber is converted into a state conducive to revulcanization after appropriate mixing and processing [21][22][23][24]. Specifically, devulcanization can be precisely characterized as a process that entirely or partially breaks poly-, di-, and monosulfidic bonds formed during vulcanization.…”