PES Plastics Alloys under Sliding Contact Condition

PES Plastics Alloys under Sliding Contact Condition

Available online at www.sciencedirect.com Procedia Engineering 36 (2012) 285 – 291 IUMRS-ICA 2011 Research on Friction and Wear Behaviors of PEEK/P...

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Available online at www.sciencedirect.com

Procedia Engineering 36 (2012) 285 – 291

IUMRS-ICA 2011

Research on Friction and Wear Behaviors of PEEK/PEI/PES Plastics Alloys under Sliding Contact Condition Jianbing Chen1,2, Qiang Guo1,*, Sigang Zhang1, Xiaoming Wang3, Xianli Shao1 1

School of Materials Science and Engineering, Shanghai University, Shanghai 201800, China 2 Department of Chemistry and Food Science, Chizhou College, Chizhou 247000, China 3 Shanghai Electric Cable Research Institute, Shanghai 200093, China

Abstract The plastic alloys of PEEK/PEI/PES were prepared with extrusion molding at 370ć in ratios of 70/30/0, 70/25/5, 65/30/5, 60/30/10, 60/35/5 (w/w). Friction and wear behaviors of the alloys were investigated under dry sliding contact condition. And wear resistances of PEEK/PEI/PES alloys were considerably improved than pure PEI and PES. The friction coefficients of the alloys were higher than the pure PEEK for 0.2-0.3. The specific wear rates of the pure PEI or PES were 4-6 times as large as the specific wear rate for the alloys of PEEK/PEI/PES, and the specific wear rate for the alloys of PEEK/PEI/PES is 7~9 times as large as the specific wear rate of the pure PEEK. The plastics alloys would produce the transferred film containing PEEK on the steel counterface. However, the transferred film of pure PES or PEI was not found on the steel ring surface. A thin symmetrical and tough transferred film in the worn steel surface against the alloy specimens could reduce friction and wear.

© 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of MRS-Taiwan Keywords: Plastic alloys; poly (ether ether ketone) (PEEK); poly (ether imide) (PEI); poly (aryl ether sulfone) (PES); wear

Nomenclature µ M F r

friction coefficient average friction moment vertical load diameter of steel ring

Ws Vs L B

specific wear rate volume of wear scar sliding distance width of wear scar

* Corresponding author. Tel.: +0086-21-69982791 or 13856651860; Fax: +0086-21-69982840. E-mail address: [email protected]

1877-7058 © 2012 Published by Elsevier Ltd. doi:10.1016/j.proeng.2012.03.042

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1. Introduction PEEK is a kind of engineering plastic with outstanding performance: high mechanical properties (strength, modulus, toughness, resistance to creep, abrasion and fatigue), high temperature resistance (Tg=143°C, Tm=338°C, continuous service temperature of 250°C, heat distortion temperature often above 300ć), good resistance to aggressive solvent, favorable processing capability, high wear resistance and self-lubrication etc. So far PEEK is a very favorable matrix material used for solid lubricant composites and quite a lot of works about the tribological behavior of PEEK and its composites have published before [1]. Poly(ether imide) (PEI) is referred to as a high performance engineering thermoplastic material in that it displays good strength, high modulus and a high glass transition temperature. PEI also demonstrates good electrical properties and remains stable over a wide range of temperatures and frequencies. It is amorphous and when unmodified it is transparent and exhibits Inherent flame resistance and low smoke evolution. It also exhibits strong relaxations in the glass transition region, which is important for comparing dynamic mechanical and dielectric behavior [2]. PEI is less expensive usually but it has become more versatile and is widely used as an amorphous thermoplastic. PES is another high performance engineering polymer that is amorphous in nature. It exhibits a high glasstransition temperature (Tg=220°C), is mechanically tough and rigid, but has a poor resistance to organic solvents [3]. The wear behavior of the composites had been studied in many literatures. But many reports about wear behavior of the composites are inorganic materials to modify the PEEK, or resins modify the PEEK. However, it is two components alloys that resins modify the PEEK, such as B. Nandan [3, 4] Less report emphasized on the three components alloys about PEEK, PEI and PES. Therefore the variations of wear behaviors and mechanism of alloys with the different content of PEEK,PEI and PES under wear mode are all investigated in this paper, In addition, as a comparison, the friction and wear properties of pure PEEK, PEI, or PES were also evaluated under identical test conditions. 2. Experimental 2.1. Preparation of polymer specimens PEEK and PES powder of 250 µm in diameter is supplied by Changchun Jilin University Super Engineering Plastics Research Co., Ltd. PEI powder of Ultem1000 is supplied by SABIC Co., Ltd. PEEK, PEI and PES were blended in ratios of 100/0/0, 70/30/0, 70/25/5, 65/30/5, 60/30/10, 60/35/5, 0/100/0, and 0/0/100 (w/w) respectively. In the codes of the alloy specimens, PEEK is shown by “K”, PEI by “I” and PES by “S”, which the quotient number of this plastic follows, e.g. K100-I0-S0 means the pure PEEK, K70-I25-S5 means PEEK:PEI:PES = 70:25:5 (w/w). Firstly, the extrusion molding and molding pressing parameters were determined through multiple optimization experiments. The particles and sheets of PEEK/PEI/PES alloys were prepared with extrusion molding, and the plates of PEEK/PEI/PES alloys were prepared with molding pressing successfully. Extrusion molding parameters: the extruder sections temperature for 310~370°C, screw speed 10~30r/min, head pressure 9~11 MPa. Molding pressing parameters: molding temperature for 370°C, at 350~370°C molding pressure for 5 MPa, at 275ć~350°C molding pressure for 10 MPa. Secondly, the specimens tested were made of the width of 7mm and length of 30 mm polishing.

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2.2 Friction and wear test The experimental apparatus for wear is outlined in Fig. 1; the sliding friction wear device is M2000A made by Zhangjiakou Xuanhua Kehua Tester Co., Ltd. The hardness were tested by TQY-I plastic ball indentation hardness supplied by Jilin Taihe Tester Co., Ltd. The steel rings of the sliding friction wear device were made of 30CrMnSiA which the surface hardness is HRC50-55. Experiments were conducted with no lubricant in laboratory air at room temperature and relative humidity of about 50±10%. The specimens that the bottom materials is tin a block with dimensions of 30mm×7mm×4mm, the test load is 200 N, the rev is 200 r/min, the cycle is 120 min, but the cycle of pure PEI or PES is for 20 min. The scar areas on the specimen, respectively, can be observed by the JC-10 optical microscope with micro scale supplied by Shanghai Fifth Optical Co., Ltd.

Fig. 1 Sliding friction wear device.

Dynamic curves of friction were calculated using Eq. 1 P

M /( r ˜ F )

(1)

The specific wear rate was calculated using Eq. 2 and the volume of wear scar was calculated in cubic millimeters as was given in Eq. 3 [5]. Ws Vs

Vs L ˜ F 7 ˜ [(S r 2 180) ˜ arcsin( B 2r )  B 4r 2  B 2 4]

(2) (3)

For each experimental condition, three identical tests were performed and the average results were reported. The widths and topography of wear scar were examined using reading microscope. 3. Results and Discussion 3.1 Variations of friction coefficient with time Figure 2(a) shows that the friction coefficient for the pure PEEK go up rapidly after 60 min, the friction coefficient reach the balance value about 0.5 after the time at which the maximum friction coefficient occurs, but the coefficient for all these alloys of PEEK/PEI/PES go up rapidly at the beginning, the maximum friction coefficient occurs after 40mins, subsequently, the friction coefficient of alloys reach the balance value about 0.7~0.8, which are higher than that of pure PEEK, as shown in Fig. 2(b) (c) (d) (e) (f). With the wear of alloys of PEEK/PEI/PES at the beginning of friction, the contacting area of the friction pairs becomes larger and larger, and adhesion becomes more and more serious. This also may be inferred by the fact that the friction coefficient was influenced by rising temperatures [6, 7], so the friction coefficient for all alloys of PEEK/PEI/PES go up rapidly at the beginning. When the temperature of the contacting area of the friction pairs reaches the balance value, the friction coefficient also reaches

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the balance value. As for the pure PEEK, it may be inferred that the contacting area of the friction pairs is more small and adhesion is not serious, the friction coefficient keeps at a lower value up to 60 min, but the contacting area of the friction pairs becomes larger and larger, and adhesion becomes more and more serious after 60 min, then reach a balance value in the end. 1.0 1.0

0.6 0.4 0.2 0.0

0

20

40

60

80

0.8 0.6 0.4 0.2 0.0

100 120

Friction coefficient

Friction coefficient

Friction coefficient

0.8

0

20

40

Time /min

(a)

100 120

0.6 0.4 60

80

100 120

Friction coefficient

Friction coefficient

0.8

40

40

0.8 0.7 0.6 0.5 0.4 0.3 0.2

0

Time /min

20

40

60

60

80

100 120

1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2

0

20

40

Time /min

(d)

80

100 120

(c)

0.9

20

20

Time /min

1.0

0

0

(b)

1.0 Friction coefficient

80

Time /min

1.2

0.2

60

1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2

60

80

100 120

Time /min

(e)

(f)

Fig. 2 Variations of friction coefficient with time for the PEEK/PEI/PES alloys: (a) K100-I0-S0, (b) K70-I30-S0, (c) K70-I25-S5, (d) K65-I30-S5, (e) K60-I30-S10, (f) K60-I35-S5.

3.2 Specific wear rate and hardness Figure 3(a) is the variations of specific wear rate for the alloys of PEEK/PEI/PES with the content of PEI when the content of PES is 5%. Figure 3(a) shows that, with the increasing of the content of PEI, the specific wear rate for the alloys of PEEK/PEI/PES increase continuously when the content of PES is 5%. Fig. 3(b) is the variations of specific wear rate for the alloys of PEEK/PEI/PES with the content of PES when the content of PEI is 30%. Figure 3(b) shows that the specific wear rate for the alloys of PEEK/PEI/PES also increases continuously with the increasing of the content of PES when the content of PEI is 30%. 7

5.7

Ws/( 10-5mm3/Nm

Ws/( 10-5mm3/Nm

6

5.6 5

5.5

4

5.4

3

5.3

2

5.2

1

5.1 0

25

30

Content of PEI (%)

(a)

35

0

5

10

Content of PES (%)

(b)

Fig. 3 Variations of alloys’ specific wear rate with the content of PEI or PES: (a) PES=5 %( wt %); (b) PEI=30 %( wt %).

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Figure 4(a) is the variations of hardness for the alloys of PEEK/PEI/PES with the content of PEI when the content of PES is 5%; Fig. 4(a) shows that, with the increasing of the content of PEI, the hardness for the alloys of PEEK/PEI/PES reduces continuously when the content of PES is 5%. Figure 4(b) is the variations of hardness for the alloys of PEEK/PEI/PES with the content of PES when the content of PEI is 30%. Figure 4(b) shows that, with the increasing of the content of PES, the hardness for the alloys of PEEK/PEI/PES also reduces continuously when the content of PES is 30%. This may be inferred by the fact that the hardness influence the specific wear rate to a certain extent, the relations between the specific wear rate and the hardness will be further investigated in the near future. 260 300

K70-I30-S0

Ball indentation hardness (N/mm2)

Ball indentation hardness (N/mm2)

K70-I25-S5

240

220

200

K65-I30-S5

180

160 K60-I35-S5

280 260 240 220 K65-I30-S5

200 180 160

K60-I30-S10

140 25

30

35

0

Content of PEI (%)

5

10

Content of PES (%)

(a)

(b)

Fig. 4 Variations of alloys hardness with the content of PEI or PES: (a) PES (w) =5%; (b) PEI (w) =30%.

Table 1 shows that the specific wear rate of the pure PEI or PES are 4-6 times as large as the specific wear rate for the alloys of PEEK/PEI/PES, and the specific wear rate for these alloys is 7-9 times as large as the specific wear rate of the pure PEEK, so we think that the specific wear rate for the alloys of PEEK/PEI/PES are improved more considerably than the specific wear rate of the pure PEI or PES. Table 1 Specific wear rate for the alloys of PEEK/PEI/PES. Specimen code

Specific wear rate (Ws) (10-5mm3/Nm)

K100-I0-S0 K70-I30-S0

0.7005 5.1334

K70-I25-S5

5.2463

K65-I30-S5

5.3518

K60-I30-S10

6.4279

K60-I35-S5

5.6989

K0-I100-S0

24.9924

K0-I0-S100

31.2548

Notes: (a) K0-I100-S0 or K0-I0-S100 were worn for 20min due to a great wear amount of the two plastics; (b) the other alloys were worn for 120min.

3.3 Analysis on the worn surfaces Figure 5(a) shows that the worn surface had a larger area to break off, and produced some striations under the stress of steel ring surface, and wear mechanism should be mainly wear of adhesion. Figure 5 (b) (d) (e) (f) shows that the topography of the worn surface of the alloys of PEEK/ PEI/PES has several deep

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furrows, and has some striations, and it can be inferred that there should be wear of adhesion and formʳ furrows.

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 5 Micrographs of the worn surfaces of the PEEK/PEI/PES alloys: (a) K100-I0-S0, (b) K70-I30-S0, (c) K70-I25-S5, (d) K65I30-S5, (e) K60-I30-S10, (f) K60-I35-S5.

Figure 6 (a) shows that a thin symmetrical and tough transferred film on the worn surface of the steel ring, but thicker transferred films can be seen in Fig. 6 (b) (c) (d), which would break off easily, and some nicks could also be observed in Fig. 6 (b) (c) (d). However, a transferred film is not observed in Fig. 6(e) and (f). It may be inferred that forming the transferred film is including the PEEK.

(a)

(d)

(b)

(e)

(c)

(f)

Fig. 6 Micrographs of the worn surfaces on the steel ring sliding against the PEEK/PEI/PES alloys specimens: (a) K100-I0-S0, (b) K70-I25-S5, (c) K65-I30-S5, (d) K60-I30-S10, (e) K0-I100-S0, (f) K0-I0-S100.

Jianbing Chen et al. / Procedia Engineering 36 (2012) 285 – 291

Forming the transferred film could avail reducing wear [8]. Therefore this may be explained by that the specific wear rate for the PEEK/PEI/PES alloys is smaller than that of pure PEI or pure PES to a certain extent. 4. Conclusions (1) The friction coefficient of alloys of PEEK/PEI/PES is about 0.7~0.8, the friction coefficient of neat PEEK is about 0.5, but the friction coefficient for all alloys of PEEK/PEI/PES go up rapidly at the beginning, the maximum friction coefficient occurs after 40mins, and the friction coefficient of alloys is higher than the friction coefficient of the neat PEEK for 0.2~0.3. (2) The specific wear rate of the neat PEI or PES is 4~6 times as large as the specific wear rate for the alloys of PEEK/PEI/PES. Especially, the neat PEI or PES can be worn out after 20 min, but the alloys were worn for 120 min in the testing. So the specific wear rate for the alloys of PEEK/PEI/PES are more improved considerably than the specific wear rate of the neat PEI or PES. (3) The alloys including PEEK all form transferred films in the surface of steel ring, but the neat PEI or PES have no any transferred film in the surface of steel ring, it is important for the alloys to have the lower specific wear rate than the neat PEI or PES. Moreover, the wear mechanism should be mainly wear of adhesion and furrow.

Acknowledgements The authors are grateful to the National Natural Science Foundation of China (No. 50975167) and Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20113108110015) for supporting of this research.

References [1] Pan G., Guo Q., Zhang W., Tian A. Wear 2009, 266: 1208. [2] Jenkins M.J. Polymer 2000, 41: 6804. [3] Nandan B, Kandpal L.D., Mathur G.N., J. Applied Polymer Science 2003, 90: 2887–2905. [4] Nandan B., Kandpal L.D., Mathur G.N., J. Polymer Science: Part B: Polymer Physics 2004, 42: 1548–1563. [5] Qiao H.B., Guo Q., Tian A.G., Pan G.L., Xu L.B. Tribol. Int 2007, 40: 106. [6] Zhang G., Yu H., Zhang C., Acta Materialia 2008, 56: 2167. [7] Paulo Davim J., Cardoso Rosária., Wear 2009 266: 798. [8] Guo Q., Wen S.Z., Luo W.L., Natural Progress 1996, 6: 597.

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