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.