1 Tribological performance of PEEK composites under the lubrication of ILs Yijun Shi a, Jian Wu b, Xiaohua Lu b a Division of Machine Elements, Luleå University of Technology, Luleå, Sweden b State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University, Nanjing , P.R. China

2 Outline  Background  Motivation & frame of work  Materials preparation and friction test  Some results Wettability of liquid lubricants Friction coefficient and wear rate Friction surface studies—SEM, AFM and EDX  Conclusions

3   Background  PEEK High chemical stability Excellent thermal and mechanical properties High friction coefficient (µ)  PEEK composites Gr, PTFE and MoS 2 and etc. as internal lubricants Some original performance of PEEK such as tensile strength and impact strength will decrease.  PEEK under lubricating oil Oil has limited working temperature, pressure...

4 Ionic liquids as lubricants Very low vapor pressure Very low vapor pressure Non-flammable substance Non-flammable substance High thermally stable High thermally stable High mechanically stable High mechanically stable Electrochemically stable Electrochemically stable

5 Citation Report Topic=(polymer + “ionic liquid” + friction OR wear) Timespan=All Years. Databases=SCI-EXPANDED, CCR-EXPANDED, IC. Most investigations steel, titanium, alloy … polymerspolymers Few investigations Related resultsAlmost no study under high applied load Ionic liquids as lubricants for polymers

6 Test property 1)Wettability of liquid lubricants 2)Friction coefficient and wear rate 3) Worn surfaces Motivation & frame of work Mediums 1) Dry condition 2) In oil: L-HM 46 (Oil) 3) In ILs: [BMIM]PF 6 (IL) Test conditions: 1) Sliding velocity: 0.7m/s 2) Load: 150 N-1500 N (1-10MPa) 3) Test time: 60 min 1) Study the tribological properties of PEEK composites in ILs; 2) Compare the lubrication effect of ILs with that of internal lubricant (PTFE) and lubricating oil.

7 Materials properties Table 1. The Main Properties of L-HM46 and [Bmim][PF 6 ] External lubricantsL-HM46[Bmim][PF 6 ] Main componentsNeutral mineral oil[Bmim][PF 6 ] Main multifunctional additiveZDDP (Zn ≤ 0.12 wt%)/ Kinetic viscosity at 40 ºC (mm 2 /S) [25] Viscosity index97172 [26] Surface tension at 40 ºC (mN/m) [27] Density at 20 ºC (kg/m 3 ) Fig. 1. Chemical structures of PEEK, ZDDP and [Bmim][PF 6 ].

8 Fig. 2. Schematic diagram of lubricating ways and frictional contact parts (Unit: mm). Friction and wear tests

9 Table 3. The contact angle of L-HM46 and [Bmim][PF 6 ] on the sliding surfaces. Wettability of liquid lubricants NumberPEEK compositesLubricants 116 vol%PTFE/PEEKInternal PTFE 2PEEKExternal L-HM46 3PEEKExternal [Bmim][PF 6 ] Table 2. Details of Different Lubricating Systems. Liquids Contact angle PEEKSteel L-HM46 9.7±1.4° 10.8±1.9° [Bmim][PF 6 ] 51.2±1.0° 52.6±1.0°

10 Anti-friction/wear performance

11 Anti-friction/wear performance

12 (Test condition: [Bmim][PF 6 ], 1500 N, 0.7 m/s, duration: 1 h). AFM studies PEEK Before After Counterpart

13 Elemental distribution (except commom elements in steel) in the counterpart worn surfaces lubricated with (a) [Bmim][PF 6 ], 1500 N for 1 h, and (b) L-HM46, 800 N for 45 minutes. Tribochemical investigation

14 Mechanism analysis

15 Tack !