Nano-hardness and wear properties of C-implanted Nylon 6

doi:10.1016/j.surfcoat.2005.06.027

Surface and Coatings Technology

Volume 200, Issues 18–19, 8 May 2006, Pages 5245-5252

https://doi.org/10.1016/j.surfcoat.2005.06.027 Get rights and content

Abstract

The technique of ion implantation was employed for improving surface hardness and wear resistance of Nylon 6. The samples of Nylon 6 were implanted with C ions to three fluences of 2 × 10¹⁵ ions cm⁻ ², 1 × 10¹⁶ ions cm⁻ ², 5 × 10¹⁶ ions cm⁻ ². The pristine and implanted samples were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, grazing incidence X-ray diffraction, electron spin resonance, nano-hardness indentation and wear testing. Nano-hardness and wear resistance of Nylon 6 was improved significantly and their friction coefficients reduced after carbon ion treatment. In particular, for 5 × 10¹⁶ ions cm⁻ ² implantation case, nano-hardness of Nylon 6 was increased to 1.096 GPa from 0.39 GPa for the unimplanted Nylon 6 corresponding to a factor of improvement about 2.81 and there was no visible wear damage on the wear surface of Nylon 6. The mechanisms underlying the improved nano-hardness and wear properties are also addressed.

Introduction

Polymeric materials are used widely in various technological applications. Nylon 6 is known to be one of the main engineering polymers and has been used in various mechanical components, electric appliances and business equipment as well as automotive industry. However, Nylon 6 components are inherently soft and low wear-resistant, and thus, the usage is limited to relatively milder service applications. The potential for applications of Nylon 6 can be significantly increased if surface hardness and wear properties can be improved.

Ion implantation can improve surface properties of polymers, such as conductivity [1], biocompatibility [2], [3], hardness and wear resistance [4]. Some polymers, such as polyimide (PI), polystyrene (PS), polycarbonate (PC) and polyphenylene oxide (PPO), had been implanted separately with B, N, O, He and metal ions for improving their surface hardness and wear properties in many studies [5], [6], [7], [8]. In the present study, Nylon 6 samples were implanted with carbon ions produced by a MEVVA (metal vapor vacuum arc) source, which is more efficient. For example, the implantation for the fluence of 2 × 10¹⁵ ions cm⁻ ² takes approximately 3 min with beam currents of 0.7–1.0 mA. The effects of implantation fluence on nano-hardness and wear properties were investigated. This work explores the potential improvements in surface hardness and wear properties of Nylon 6 by carbon ion beam treatment.

Section snippets

Experimental details

Nylon 6 was manufactured by Yueyang Petro-Chemical Complex, Sinopec Corp. and its trademark was BALING.

The Nylon 6 samples were machined into dimensions of 10 mm × 6.9 mm × 6 mm after injection moulding. The samples were ground using no. 900 sandpaper in order to control their surface roughness, which was tested by a SP-120 model profilometer, and R_a value was 0.073 μm.

A MEVVA source implanter was used at an accelerating voltage of 55 kV. The fluence(i.e., dose) was calculated by the control

Nano-hardness tests

A nano-indentation technique was used to determine surface hardness of the pristine and implanted Nylon 6 samples. The results for fluence dependence of hardness of C-implanted Nylon 6 are given in Fig. 2. It can be seen that the nano-hardness increased with increasing implantation fluence. The hardness of 2 × 10¹⁵ ions cm⁻ ², 1 × 10¹⁶ ions cm⁻ ² and 5 × 10¹⁶ ions cm⁻ ² C-implanted Nylon 6 was dramatically increased to 0.519 GPa, 0.653 GPa and 1.096 GPa, respectively, from 0.39 GPa for the unimplanted

Nano-hardness

The surface hardness of Nylon 6 was improved by carbon ion-beam treatment and the hardness value increased with increasing fluence, particularly for the high fluence of implantation, the hardness of Nylon 6 increased to 1.096 GPa from 0.39 GPa for the unimplanted Nylon 6, corresponding to a factor of improvement of about 2.81. The hardness improvements are correlated with cross-linking of polymers induced by ion implantation. The cross-linking occurring among the molecular chains of polymers

Conclusions

(1)
Surface hardness and wear properties of Nylon 6 were improved significantly after ion implantation of carbon. The hardness of Nylon 6 increased and its wear volume reduced with increasing fluence. In particular, for the high fluence of 5 × 10¹⁶ ions cm⁻ ², the hardness of Nylon 6 increased to 1.096 GPa from 0.39 GPa for the unimplanted Nylon 6, corresponding to a factor of improvement about 2.81, and there was no visible wear damage on the wear surface of the 5 × 10¹⁶ ions cm⁻ ² C-implanted Nylon 6.

Acknowledgements

We thank Professor Zhang T. H. from the Institute of Low Energy Nuclear Physics of Beijing Normal University for the help with TRIM calculations, Professor Shen D.Y. from Institute of Chemistry of Chinese Academy of Sciences and Professor Wang K. H. from Chemical Engineering Department of Tsinghua University for help with FT-IR analyses.

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