Vol. 55 No. 1

Material Science and Technology of Japan, 55㸦2018㸧21㹼25

21

Regular PaperSliding Characteristics of Rubber O-ring Coated by Diamond-likeCarbon (DLC) in Medium Vacuum
Katsuyuki FUJIMURA1*, Katsuhiko TASHIRO2,3, Shuji YAMAMOTO3
and Osamu TAKAI1,3
1

Department of Industrial Chemistry, Graduate School of Engineering, Kanto Gakuin University: 1-50-1,
Mutsuurahigashi, Kanazawa-ku, Yokohama-shi, Kanagawa 236-8501, Japan

2

Research Advancement and Management Organization Kanto Gakuin University: 1-50-1, Mutsuurahigashi,Kanazawa-ku, Yokohama-shi, Kanagawa 236-8501, Japan
3

Materials and Surface Engineering Research Institute, Kanto Gakuin University: 1162-2, Odawara-shi,Kanagawa 250-0042, Japan
Received Sep. 22, 2017; accepted for publication Dec. 4, 2017
Abstract
The sliding behavior of a rubber O-ring coated by diamond-like carbon

in the medium-vacuum deposition

method was evaluated. The superiority of rubber members has been pursued for the valve structure of pneumatic
control equipment in the automation field. It has been considered that a DLC-coated rubber member which has lowfriction with superior wear resistance could be applicable to improve the performance of the sliding members. For
cost reduction of the DLC film formation, the medium-vacuum method was adopted for the rubber coating. The
oil-less sliding friction and the wear characteristics of the DLC on the rubbers were examined over a 2,000 m slide
distance, which is the practical requirement in industry. As a result, it was confirmed that the oil-less sliding friction
when coated with DLC for more than 10 min deposition time was sufficient for practical use.
Keywords: Rubber, Medium-Vacuum, PCVD, DLC, Friction

1.

Introduction

feed the oxygen or anesthetic gas in medical equipment because

In recent years, resource and energy saving have become

the wear of the plug is non-negligible, which might cause risks torequirements for making environmentally friendly products,

the patient. Because clean and highly durable use is needed in thewhile the technology has rapidly advanced [1-3]. Among the new

medical field, ethylene propylene rubber (EPDM) based

technologies, oil-less sliding is receiving a lot of attention. DLC

components with an atoxic 10-year life-time on the condition offilm is used as a clean sliding member in semiconductor

5 time-connections (10 mm per one sliding) is required. DLC is

manufacturing equipment, food processing, medical fields and soalso regarded as a human friendly material and the good sliding

on, due to its superior tribological properties such as the small

performance

friction and superior wear resistance [4]. DLC technology has

semiconductor industries. However, only a film deposition

been developed for the tribological enhancement of the metal,

method equipped with a high-vacuum pump (0.1 to 0.001 Pa) hasceramics materials and so on. Most of the papers regarding DLC

so far been used for the DLC formation. On the other hand,study have been concerned with rigid materials [5]. There aremedium-vacuum (1 to 10 Pa) plasma chemical vapor deposition

few DLC applications reported for an elastic medium such as(MV-PCVD) equipment is desired to make the DLC film

rubber [6-8]. Nitrile rubber (NBR) is one of the most important

formation feasible at reduced cost.

ofrubbermembersinthemedicalandIn this study, DLC derived from the MV-PCVD method wasartificial materials for industrial use. NBR is used for the sliding

members in the valve structure of pneumatic control equipment.  coated   on NBR and EPDM flat substrates and the tribological
Lower friction properties are required for the joint members to 
*Corresponding author: k-fujimura@cenken.co.jp(21)

properties were investigated by the ball-on-disk test. Furthermore,