Ultrasonic Aided Extrusion of CNT- And CNF-Filled SBR Compounds and Properties of Their Vulcanizates

Abstract

Ultrasonically assisted single screw extrusion of styrene–butadiene rubber (SBR) compounds filled with multiwall carbon nanotubes (CNT) up to 20 phr and carbon nanofibers (CNF) up to 35 phr was carried out. The effects of ultrasonic amplitude on processing characteristics, rheology, extractable amount, vulcanization behavior, mechanical properties, abrasion, electrical resistivity, and morphology were investigated. Ultrasonically treated compounds showed an increase in viscosity and unextractable content in both CNT- and CNF-filled compounds. A decrease in the induction time of curing with amplitude was observed in CNT-filled compounds. However, the induction time of CNF-filled compounds showed more complex behavior with amplitude. The final cure torque, crosslink density, modulus, and tensile strength showed a maximum at an intermediate amplitude in filled vulcanizates. An increase in the glass transition temperature (Tg) and a decrease in tan δ at Tg with amplitude were observed in CNF- and CNT-filled vulcanizates. At the same time, tan δ in the range of 0–60 °C of these vulcanizates showed, respectively, a minimum and a continuous increase with amplitude. CNF-filled vulcanizates exhibited improved abrasion resistance with optimum results at an amplitude of 5.0 μm. The effect diminished with increasing CNF loadings. Improvements in abrasion resistance of CNT-filled vulcanizates were observed at certain amplitudes at low CNT loadings only. Ultrasonic treatment caused a significant reduction in the electrical percolation threshold of CNF- and CNT-filled vulcanizates. Atomic force microscope analysis showed a generation of unique CNT agglomerates by ultrasonic treatment, suggesting an increase of rubber–filler interaction. High resolution scanning electron microscopy analysis of vulcanizates showed better dispersion of ZnO by ultrasonic treatment.

Ultrasonic treatment of polycarbonate/carbon nanotubes composites

“…The commonly used methods to prepare polymer composites are in-situ polymerization [13][14][15][16], solution methods [17][18][19], and melt processing [3][4][5][20][21][22]. Though good dispersion of CNTs can be achieved by in-situ polymerization, there are only limited numbers of polymers that can be used in in-situ polymerization.…”

“…However, one drawback of melt processing method is that the dispersion of nanofillers in the products is not as good as using the other two methods. Over the past decade, high power ultrasound has been proven to be an efficient method to improve the dispersion of nanofillers in polymer matrix [4,[20][21][22][23][24][25]. Swain and Isayev studied the high density polyethylene (HDPE)/clay nanocomposites prepared by a single screw compounding extruder attached with an ultrasound die.…”

Effect of carbon nanotubes with different lengths on mechanical and electrical properties of silica-filled styrene butadiene rubber compounds

“…But the formation of the moieties is detrimental to the dynamic mechanical properties, resulting in a tradeoff between electrical and dynamic properties. Various reports can be found in literature [14][15][16][17] describing the effects of CNT on rubber compounds. However, the effects of CNT addition on the dynamic and electrical properties of tire treads have not yet been systematically investigated.…”

Effects of ultrasound on the conformational and crystallization behavior of isotactic polypropylene polymerized with different Ziegler—Natta catalyst

“…Since the ultrasound can accelerate chemical reactions, modify the rheolog ical and mechanical properties, and so on, it is widely applied in polymer processing [1][2][3][4][5][6]. Isayev et al stud ied the processing of polymers using high power ultra sound and found that ultrasonic vibration during extru sion modified the die characteristics [7][8][9][10][11][12]. Khamad and co workers studied the extrusion process of HDPE containing a small amount of butyl rubber under ultra sonic irradiation and found the increase of crystallinity, the reduction of structural defects and the enhance ment of mechanical properties.…”