Post on 27-May-2015
description
OCTOBER 2013
Reyes-Reyes J. L. 1, Chiñas-Castillo F. 1, Sánchez Rubio M. 1
& Lara-Romero J. 2 & Hüirache Acuña R. 2
1 Instituto Tecnológico de Oaxaca, Department of Mechanical Engineering 2 Universidad Michoacana de San Nicolás de Hidalgo, Department of Chemical Engineering CONTACT: fernandochinas@gmail.com rerjl@gmail.com
“On the tribological perfomance of carbon nanotubes
reinforced Acrilonitrile-Butadiene-Styrene polymer”
Introduction
In this study the tribological effect of adding CNTs in ABS thermoplastic matrix through melted compounding technique is presented. Friction and wear performance of the nanocomposite were investigated on a pin-on-disc tribometer for a range of loads. Addition of up to 0.5%wt CNTs into the ABS matrix highly increased the wear resistance and nanoindentation tests indicate a significant improvement in Young’s modulus and hardness. The worn surface of ABS/CNTs nanocomposites was examined with SEM and optical microscopy showing that the wear mechanism shifted from abrasive wear in ABS matrix to adhesion and small delamination wear for the nanocomposite. ABS/CNTs nanocomposites with a low content of CNTs are a candidate material for engineering application.
Methods and materials
Carbon nanotubes were prepared by spray pyrolysis as described in reference [5]. Commercially available ABS general propose MG47 (medium impact) was purchased from plastic GE. A pin-on-disc tribometer was used for this study to perform wear tests according to ASTM G99-95a. Measurements of hardness and modulus of elasticity were obtained by a nanoindenter Hysitron Ubil.
[5] J. Robles–Nuñez, F. Chiñas-Castillo, M. Sanchez-Rubio. J. Lara-Romero, R. Huirache-Acuña, S. Jimenez-Sandoval, and G. Alonso-Nuñez, ”Improved hydrothermal synthesis of MoS2 sheathed carbon nanotubes”, Chemical paper, Vol. 66, No. 12 pp. 1130-1136 (2012)
Methods and materials
The CNTs were added as prepared. ABS pellets and CNTs were mixed in a mechanical mono screw extruder. A higher dispersion was obtained after a second extrusion of ABS+CNT. The resultant product went through a moulding injection process to get nanocomposite disc samples of 10 mm thickness and 25.4 mm in diameter. For tribological tests 6 mm diam. AISI52100 steel balls were used.
ABS MATRIX
MWCNTs
Methods and materials
ABS Pellets ABS+0.1% MWCNTs ABS+0.5% MWCNTs
Pellets ABS (virgin) MWCNTs Dried Hopper
Mini pellet mill Bands Filaments of ABS
Next
Methods and materials
Pellets ABS in Hopper
ABS
ABS+0.1% MWCNTs
ABS + CNT NANOCOMPOSITES
ABS+0.3% MWCNTs
ABS+0.5% MWCNTs
MATRIX
TEM of ABS+CNTs nanocomposites
FT-IR Spectra of ABS and ABS+CNTs
• Benzene ring (3062, 3028,1603-1453,
760-699 cm -1)
• Nitrile (2238 cm -1)
• Methylene (2921 & 2851 cm -1)
Elastic modulus of ABS and ABS+CNTs
Hardness of ABS and ABS+CNTs
Tribometer “pin-on-disc”
Test conditions
• Load 5, 10 & 12 N
• Constant speed 0.4 m/s
• Time 60 min
• Temperature Ambient
Friction coefficient and wear ABS matrix
As load increases from 5 - 12N wear increases and friction coefficient decreases.
Wear of ABS matrix vs. nanocomposites
Wear of ABS matrix and nanocomposites
SEM images of wear track (load 5N)
ABS matrix
ABS+0.1 CNTs
ABS+0.3 CNTs
ABS+0.5 CNTs
Sliding direction
Wear abrasive
Cracks
Fatigue-Delamination
Deformation plastic and adhesion
SEM images of wear track (load 12N)
ABS matrix
ABS+0.1 CNTs
ABS+0.3 CNTs
ABS+0.5 CNTs
Wear abrasive
Plastic flow
Cracks
Adhesion and Delamination-Fatigue
Plastic
Deformation and flow
Conclusions • Hardness and elastic modulus is HIGHER with higher CNTs content.
• Wear is REDUCED with higher CNTs content. • Wear mechanism is shifted from abrasion to adhesion and delamination
with higher CNTs content.
• Higher content of CNTs reduces wear debris, increasing cohesion force of the polymer.
• For ABS friction is REDUCED as load is higher
• Adding CNTs to ABS causes friction to pass a transition from elastic contact to plastic one. Load can vary the temperature of visco-elastic transitions in polymers and thereby the mechanism of friction.