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Tribological performance of PEEK composites under

the lubrication of ILs

Yijun Shia, Jian Wub, Xiaohua Lub

a Division of Machine Elements, Luleå University of Technology, 97187 Luleå, Swedenb State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University,

Nanjing 210009, P.R. China

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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

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Background

PEEKHigh chemical stabilityExcellent thermal and mechanical propertiesHigh friction coefficient (µ)

PEEK compositesGr, PTFE and MoS2 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...

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Ionic liquids as lubricants

Very low vapor pressure

Non-flammable substance

High thermally stable

High mechanically stable

Electrochemically stable

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Citation ReportTopic=(polymer + “ionic liquid” + friction OR wear)Timespan=All Years. Databases=SCI-EXPANDED, CCR-EXPANDED, IC.

Most investigations steel, titanium, alloy …

polymersFew investigations

Related results Almost no study under high applied load

Ionic liquids as lubricants for polymers

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Test property1) Wettability of liquid lubricants2) Friction coefficient and wear rate3) Worn surfaces

Motivation & frame of work

Mediums1) Dry condition2) In oil: L-HM 46 (Oil)3) In ILs: [BMIM]PF6 (IL)

Test conditions:1) Sliding velocity: 0.7m/s2) 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.

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Materials properties

Table 1. The Main Properties of L-HM46 and [Bmim][PF6]

External lubricants L-HM46 [Bmim][PF6]Main components Neutral mineral oil [Bmim][PF6]Main multifunctional additive ZDDP (Zn ≤ 0.12 wt%) /Kinetic viscosity at 40 ºC (mm2/S) 45.9 89.1 [25]Viscosity index 97 172 [26]Surface tension at 40 ºC (mN/m) 43.4-48.8 31.85 [27]Density at 20 ºC (kg/m3) 872.8 1370.0

Fig. 1. Chemical structures of PEEK, ZDDP and [Bmim][PF6].

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

Friction and wear tests

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Table 3. The contact angle of L-HM46 and [Bmim][PF6] on the sliding surfaces.

Wettability of liquid lubricants

Number PEEK composites Lubricants

1 16 vol%PTFE/PEEK Internal PTFE

2 PEEK External L-HM46

3 PEEK External [Bmim][PF6]

Table 2. Details of Different Lubricating Systems.

LiquidsContact angle

PEEK Steel

L-HM469.7±1.4°

 

10.8±1.9°

 

[Bmim][PF6]51.2±1.0°

 

52.6±1.0°

 

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Anti-friction/wear performance

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Anti-friction/wear performance

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(Test condition: [Bmim][PF6], 1500 N, 0.7 m/s, duration: 1 h).

AFM studies

PEEKBefore After

Counterpart

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Elemental distribution (except commom elements in steel) in the counterpart worn surfaces lubricated with (a) [Bmim][PF6], 1500 N for 1 h, and (b) L-HM46, 800 N for 45 minutes.

Tribochemical investigation

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Mechanismanalysis

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Tack !