27 Structures and Mechanical Properties of PEEK-PEI-PES Plastics Alloys Blent by Extrusion Molding Used for Cable Insulating Jacketing.pdf

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Procedia Engineering 36 ( 2012 ) 96 – 104

IUMRS-ICA 2011

Structures and Mechanical Properties of PEEK/PEI/PES

Plastics Alloys Blent by Extrusion Molding Used for Cable

Insulating Jacketing

Jianbing Chen 1,2 , Qiang Guo 1 *, Zhengping Zhao 1 , Xiaoming Wang 3 , Chunlai

Duan 3

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 PEEK/PEI/PES plastic alloys were processed by twin-screw extruder at 370 ° C with five mass ratios of 70/30/0,

70/25/5, 65/30/5, 60/30/10, and 60/35/5, respectively. Their thermal properties and crystallization behavior were

investigated by the differential scanning calorimetry. The measured results showed that all the plastic alloys had a

single glass-transition temperature ( Tg ), which revealed good compatibility among the three members of PEEK, PEI

and PES. For the alloy with the mass ratio of 70/30/0, the minimum Tg of 160.6 ° C was obtained, but the alloy of

60/35/5 had the maximum Tg of 164.5 ° C, which indicate that PEI, PES and the amorphous plastics could increase Tg

of the PEEK alloys and was 20 ° C higher than that of pure PEEK. The melting points ( Tm ) of these alloys were from

334.4 ° C to 336.3 ° C and their crystallinity degrees were from 35.8% to 37.8%, whereas both were slightly higher than

that of pure PEEK. However, the cold crystallization temperatures of the alloys were lower than that of pure PEEK,

which could be attributed to the reason that the rheological properties of the alloys were improved by PEI. Tensile

strength of the plastic alloy with the ratio of 60/30/10 presented the maximum value of 108MPa and was higher than

that of pure PEEK. After thermal ageing at 158 ć (below Tg ) or 178 ć (above Tg ) respectively for 168h, their tensile

strengths decreased only slightly, but elongation rates at break reduced significantly, of which thermal ageing above

Tg would recede the elongation at break more severely. The plastic alloy of 60/30/10 could be used as the cable

insulating jacketing for nuclear power station.

Keywords: Poly (ether ether ketone) (PEEK); poly (ether imide) (PEI); poly (aryl ether sulfone) (PES); plastic alloys

* Corresponding author. Tel.: +0086-21-69982791 or 13856651860; Fax: +0086-21-69982840.

E-mail address: guoq@shu.edu.cn

doi: 10.1016/j.proeng.2012.03.016

Jianbing Chen et al. / Procedia Engineering 36 (2012) 96 – 104

Nomenclature

glass transition temperature

İ elongation at break

melting temperature

G original distance of standard line

crystallization temperature

ı tensile strength

'Hm

enthalpy of melting

P peak load

degree of crystallinity

b width of specimens

'Hc

crystallization enthalpy

d thickness of specimens

Tg*

glass transition temperature calculated by Fox equations Ɏ weight fraction

1. Introduction

The application of thermoplastic composites for seal, gear and bearings provides alternatives to

metallic components which have been widely developed. The reinforcing additives such as short carbon

fibre, glass fibre [1, 2] and inorganic or metallic powder fillers [3] were used already for improvement of

high performance engineering plastics such as PEEK, but significantly higher price and lower glass

transition temperature than PEI and PES have limited its application in industry. The blends as plastics

alloys in between PEEK and PEI, PES, PPS or PTFE were also studied to obtain excellent comprehensive

properties [4]. However, few reports emphasized on the three components plastic alloys containing PEEK.

Several ternary plastic alloys of PEEK, PEI and PES with lower cost could be prepared by extrusion

blending process, and structures and properties of the alloys with the different content of PEEK, PEI and

PES were investigated for the insulating sheath of special cable used in nuclear power in this paper.

2. Experimental

2.1. Preparation of plastic specimens

PEEK and PES powder of 250 μm in diameter was supplied by Changchun Jida Engineering Plastics

Research Co., Ltd. PEI powder of Ultem1000 was 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. Before blending, the three polymers were completely dried overnight in an air-

circulated oven at 150 ° C. The polymers were melt-blended in TSE-30A twin-screw extruder supplied by

Nanjing RuiYa Polymer Co., Ltd. Extrusion molding parameters include the sections of extruder

temperature of 310~370 ° C, screw speed of 10~30r/min, and head pressure of 9~11MPa.

2.2 Differential scanning calorimeter analysis

A Q2000 Type Perkin Elmer differential scanning calorimeter (DSC) of TA Instruments was used to

obtain the thermograms of pure PEEK, PEI, PES and the alloys of PEEK/PEI/PES. The temperature used

was 50-400 ° C with nitrogen atmosphere and the samples were heated at rate of 10 ° C·min í1 , then the

samples were cooled at rate of 10 ć min í1 to room temperature.

Degree of crystallinity (Xc) is a positive factor on mechanical properties of PEEK and could be

calculated as Eq. (1).

Jianbing Chen et al. / Procedia Engineering 36 (2012) 96 – 104

(%)

100

(1)

where the ' Hc can be obtained from the area that is enclosed by the peak of DSC melting curves and the

baseline, and ' Hm is the melting enthalpy when the degree of crystallinity is 100%, which is 130J/g [5, 6].

2.3 Mechanical properties examination

Elongation at break and tensile strength were carried out on a universal testing machine which is

DELL-20000 tensile tester supplied by Shanghai Dengjie Machine Co., Ltd. Experiments were conducted

in laboratory air at room temperature and relative humidity of about 50±10%, and the tensile speed of

5mm/min. Dumbbell specimens were prepared by omnipotent sample maker.

0 u

100

(2)

(3)

3. Results and Discussion

3.1 Influence of compositions of the alloys on their thermal properties and crystalline behaviours

Figure 1 showed that Tg of pure PEEK, PEI and PES are 143.3 ° C, 216.5 ° C and 230.2 ° C respectively,

but all the alloys of PEEK/PEI/PES exhibited a single glass-transition temperature ( Tg ) between 160.6 ° C

and 164.5 ° C. The alloy of 70/30/0 presented the minimum Tg at 160.6 ° C, but the alloy of 60/35/5 had the

maximum Tg at 164.5 ° C, which was higher than that of pure PEEK about 20 ° C when the PEI or PEI and

PES were added. This revealed that PEEK, PEI and PES had a good compatibility.

P E E K /P E I/PE S

100/0/0

70/30/0

70/25/5

65/30/5

60/30/10

60/35/5

0/100/0

0/0/100

100

150

200

250

300

350

400

Temperature/ q C

Fig. 1 DSC traces of rising temperature for the alloys of different content of PEEK/PEI/PES.

PEI and PES had an intense reciprocity and a good blending compatibility [7], and the blends of PEEK

and PES had two Tg , which were very close, showing that the blends had partial compatibility [8].

However, the blends of PEEK and PEI had a good compatibility [9]. Therefore it can be inferred that PEI,

as a bulking agent, could improve the compatibility of PEEK and PES, which was the reason why the

alloys of PEEK/PEI/PES had a good compatibility. It had also been reported that the addition of PEI can

Jianbing Chen et al. / Procedia Engineering 36 (2012) 96 – 104

restrain the crystallization velocity of PEEK [9], and the addition of PES can restrain the crystallization

velocity of PEEK [10, 11]. It can also been seen in Fig. 1 that the pure PEEK doesn't have any

crystallization peak, but the alloys of PEEK/PEI/PES or PEEK/PEI have the crystallization peak in the

course of rising temperature.

For the miscible blends system, there are many theoretical equations to interpret the relationship

between blend compositions and Tg . Fox equations is used to determine the phase compositions of the

PEEK/PEI/PES alloys. In theory, Tg , which can be obtained by DSC in the experiments, would comply

with Fox equations approximately. However, Tg* are higher than Tg of alloys which were obtained by

experiments. For Tg* , the influence by PES with high Tg is more serious than that by PEI. This also may

be inferred by the fact that the compatibility of PEEK and PES can be improved by adding PEI, because

PEI and PES had an intense reciprocity and the blends of PEEK and PEI had a good compatibility [7, 9].

Fox equations:

Tgb

(4)

(5)

where Tgb Tg1 , Tg2 , and Tg3 are the glass transition temperatures of the blends, component 1, 2 and 3,

and w1 , w2 and w3 are the weight fractions of component 1, 2 and 3, respectively.

With the increasing of the weight fraction of PEI and PES from 30% to 40%, it can be seen in Table 1

that Tg of the alloys of PEEK/PEI/PES will be increased from 160.6 ° C to 164.5 ° C.

Tgb

Table 1 Tg of the PEEK/PEI/PES alloys.

Ratios (w/w)

100/0/0

70/30/0

70/25/5

65/30/5

60/30/10

60/35/5

0/100/0

0/0/100

Tg /°C

143.3

160.6

161.2

163.0

163.2

164.5

216.5

230.2

Tg* /°C -- 159.8 159.6 162.6 166.1 165.7 -- --

Figure 2 illustrates that adding PEI or PEI and PES can make the crystallization temperature of the

alloys deviate from high temperature to low temperature, which may be inferred by the fact that adding

PEI or PES or PEI and PES have some influences on the crystallization temperature of alloys. It had been

reported that the amorphous diluent layers can increase interlamination fluidity of the blends, form easily

the ordered arrangement of chain segments, and increase the degree of crystallinity [12].

PEEK/PEI/PES

100/0/0

70/30/0

70/25/5

65/30/5

60/30/10

60/35/5

100

150

200

250

300

350

400

Temperature/ q C

Fig. 2 DSC crystallization curves of dropping temperature for the alloys of different content of PEEK/PEI/PES.

100

Jianbing Chen et al. / Procedia Engineering 36 (2012) 96 – 104

The crystallinity degree of the alloys appeared from 35.8% to 37.8% in Table 2, in which the

maximum value of 37.8%, which was higher than that of pure PEEK was for the alloys with ratio of

60/30/10. Therefore, it can be inferred that PEI or PES and PEI would play the role of the amorphous

diluent layers and increase the interlamination fluidity of the alloys, resulting in avail to ordered

arrangement of PEEK chain segments. However, the cold temperature of crystallization for the alloys was

lower than that of pure PEEK, meaning that the presence of PES and PEI increased the crystallinity

degree of PEEK.

Table 2 ' Hc, Tc, Tm, ' H*m and Xc of the pure PEEK and the alloys of PEEK/PEI/PES.

Ratios(w/w)

100/0/0

70/30/0

70/25/5

65/30/5

60/30/10

60/35/5

' Hc (J/g)

43.77

32.75

32.87

31.40

29.45

27.93

Tc / ° C

298.36

291.89

292.27

290.94

290.55

289.97

Tm / ° C

336.44

336.29

335.51

335.15

335.14

334.36

' H*m (J/g)

36.31

26.56

26.66

24.51

24.68

22.55

33.7

36.0

36.1

37.2

37.8

35.8

3.2 Influence of compositions of the alloys on their tensile strength and elongation at break

Tensile strength and elongation at break of the alloy specimens, including plates and sheets, are listed

in Table 3. The tensile strength and elongation at break of the alloy plates were from 102MPa to 108MPa

and from 3.42% to 4.06% respectively, and higher than that of the pure PEEK with the exception of the

60/35/5 alloy. The maximum tensile strength was 108.1MPa for the alloy of 60/30/10, and the maximum

elongation at break was 4.06% for the alloy of 60/35/5. As a comparison of the alloy sheets, tensile

strength were lower and elongation at break were higher than that of the alloy plates.

Table 3 Tensile strength and elongation at break of the alloys of PEEK/PEI/PES.

100/0

60/30/1

Ratios (w/w)

70/30/0

70/25/5

65/30/5

60/35/5

0/100/0

0/0/100

tensile strength of alloy plates /MPa

104.0

105.4

104.5

106.4

108.1

102.1

115.6

97.1

tensile strength of alloy sheets /MPa

91.0

91.3

90.5

86.0

94.7

89.8

elongation at break of alloy plates /%

1.88

3.78

3.72

3.56

3.42

4.06

7.63

6.97

elongation at break of alloy sheets /%

150

130

140

130

140

170

In Fig. 3(a), the tensile strength increased firstly, then decreased with increasing of the content of PEI

from 25wt% to 35wt%, and reached the maximum value 106.4 MPa when the content of PEI was 30wt%.

Figure 3(b) shows that the elongation at break decreased firstly, and then increased with increasing of the

content of PEI, and reached the maximum value 3.56% when the content of PEI was 35wt%. However,

crystallinity degree also increased firstly, then decreased with increasing of the content of PEI from

25wt% to 35wt% when the content of PES was 5wt%. Therefore, it would be inferred that tensile strength

and elongation at break were influenced seriously by crystallinity degree of the alloys.

In Fig. 4(a), the tensile strength increased continuously with increasing of the content of PES from 0 to

10wt% when PEI content was 30wt%, and reached the maximum value of 108.1MPa when the content of

PES was 10wt%. Figure 4(b) shows that elongation at break decreased continuously with increasing of

PES content from 0 to 10wt%, and reached the minimum value of 3.42% when the content of PES was

10wt%. However, in Table 2, the degree of crystallinity increased continuously with increasing of PES

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