Structure and Properties of novel modified polyester fibers

Ningning Wu1, 2, a, Liqian Huang1, 2, b and Jianyong Yu 2, 3, c

1College of Textile, Donghua University, Shanghai, 201620, China

2Key Laboratory of Textile Science &Technology, Ministry of Education, Shanghai, 201620, China

3Modern Textile Institute, Shanghai, 201620, China

awuning0201@163.com, bhlqian@dhu.edu.cn, cyujy@dhu.edu.cn

Keywords: Modified Polyester fibers; Structure; Mechanical properties; Thermal properties.

Abstract: The structure and properties of the fiber affect its processing and wearing performance of

the textile product. There are 3 kinds of novel polyester fibers modified by copolymerization. To

make good use of these modified polyester fibers and predict their processing and wearing

performance, the structure and properties of the fibers were characterized by cross section,

crystallinity, moisture regain, tensile test, DSC and TG. Results show that the 2 of the modified

fibers are profiled fibers with lower crystallinity and higher moisture regain. The mechanical

properties of the modified fibers are worse than that of the ordinary polyester, but much better than

cotton fiber. The modified polyester fibers are more thermal-sensitive than ordinary polyester fiber.

The heat treatment temperature of them in the textile processing should be controlled more carefully

than ordinary polyester fibers.

Introduction

It is well known that, in recent years the cotton fibers continue running at high price. From

long-term interests, cotton will increasingly become a short supply resource[1]. It is significant to

explore a way to produce the new productions with both good moisture absorption like cotton fabric

and durability like polyester fabric. It not only can solve the excessive production of polyester fibers,

but also alleviate tensions in the domestic cotton supply[2].

In this article, the structure and properties of 3 kinds of novel polyester fibers, which are

chemically modified by copolymerization, were studied and compared with ordinary polyester fiber

and cotton fiber to explore their application in cotton-like textile production.

Experimental Materials. Three kinds of modified polyester fibers, which were modified by adding

3rd

and/or 4th

monomer in copolymerization to improve the properties of fiber, were used in this

study. As reference samples, cotton fiber and ordinary polyester fiber were also used. The fiber

specifications are shown in Table 1.

Table 1. Specification of the fibers

f -1 f -2 f-3 f-4 f-5

Material Modified

polyester I

Modified

polyester II

Modified

polyester III

Ordinary

polyester

Combed

cotton

The fineness /dtex 1.63 1.52 1.62 1.40 2.02

The length / mm 38 38 38 38 35.6

Advanced Materials Research Vols. 821-822 (2013) pp 55-59Online available since 2013/Sep/18 at www.scientific.net© (2013) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.821-822.55

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Structure and Properties Characterization

All tested samples were conditioned under standard atmosphere environment，by referring to the

standard GB6529-2008 "for textiles and wet test with standard atmosphere”.

Cross section of the fibers. The cross section of fibers were observed on an optical microscope.

Crystallinity.X- Ray diffraction: Japan Rigaku producing D / MAX 2550 PC – based.

Moisture regain. The samples were tested in accordance with the GB/T6503-2008 "test method

for chemical fiber moisture regain”.

The mechanical properties of the fiber. The tensile tests were performed on XQ - 2 fiber

tensile tester with, test speed of 100mm/min, 30 times of each sample were carried out.

Thermal properties. DSC measurement: The whole test process is under the atmosphere of N2,

and the airflow is 20 ml/min. Take samples around 5 mg, placed in the aluminum seal in one

crucible, the other crucible with sealed as for reference. The sample was heated up with the heating

rate of the 10°C/min to 300°C. And DSC curve was obtained.

TG measurement: the fibers were tested in the N2 environment, from room temperature to 600°C,

the heating rate is 10°C/min.

Results and Discussions

Cross profile of fober

(a) (b) (c)

(d) (e)

Fig.1. Cross section of the fibers (×50); (a) f-1;(b) f-2;(c) f-3;(d)f-4;(e)f-5

As Fig.1 shows, the cross-section of f-1 is hollow, that of f-2 is circular, and f-3 with a triangular

cross-section. The ordinary polyester fiber f-4 is of round shape, and cotton fiber is kidney shape

with a cavity as it is well-known. The non-circular cross section of f-1 and f-3 would be helpful to

improve the hand, heat retention and luster of textiles.

Crystallinity

Table 2. Crystallinity of fibers

f -1 f -2 f-3 f-4 f-5

crystallinity /% 36.0 34.8 34.1 38.9 65.9

As the above table shows the crystallinity of modified polyester fibers are less than ordinary

polyester fiber, because the added monomers in the molecules destroy the regularity of the structure

of ordinary polyester. This will help to improve the moisture absorption and dyeability of the fibers.

56 Advances in Textile Engineering and Materials III

But there is no doubt that the crystallinity of cotton fiber is much greater than that of polyester

fibers because of the strong interaction of cellulose molecules.

Moisture regain. Moisture regain is the percentage of discrepancies between wet weight and dry

weight by dry weight.

Table 3.Moisture regain of fibers

f-1 f-2 f-3 f-4 f-5

moisture regain/% 1.17 1.33 1.45 0.4 5.4

It can be seen from Table 3, the moisture regain of 3 kinds of modified polyester fiber is higher than

that of ordinary polyester fiber, but much less than that of cotton fiber. The three modified fibers are

made of joined long chains with hydrophilic groups on the basic structure of ordinary polyester, but

compared with the high content of –OH groups on cellulose molecules, the content of 3rd

and 4th

monomer on polyester molecules are limited.

Tensile properties. Strength and elongation of the fiber is the basic mechanical property, which

influence the processing of the products and the wearing performance of clothing.

Table 4. Tensile properties of fibers

f-1 f-2 f-3 f-4 f-5

Breaking strength

cN/dtex 3.63 3.75 2.53 5.68 3.24

elongation at break % 20.07 32.56 20.92 31.24 9.75

The specific work

cN/dtex 0.35 0.79 0.33 1.28 0.14

Modulus cN/dtex 22.87 30.87 27.40 37.21 21.72

From Table 4, the mechanical properties of modified polyester fibers are worse than that of the

ordinary polyester, but much better than that of cotton fiber. The breaking strength of fibers are:

f-4>f-2>f-1>f-5>f-3. The lowest strength of f-3 may be caused by the uneven force formed along

the fiber due to the triangular cross-section of the fiber, which may thus limits its application scope

to some extent.

The modulus is an important indicator about flexibility of fiber. Makes the numerical

comparison: f-4>f-2>f-3>f-1>f-5. The modulus of 3 modified polyester fibers are smaller than that

of ordinary polyester fiber, but larger than that of cotton fiber. The smaller the fiber modulus is, the

better softness fabric is. In brief, the tensile properties of f-3 and f-1 are more “cotton-like” than f-2

and f-4.

Thermal properties. Thermo-gravimetric analysis is a technology which probe the relationship

between material mass and the temperature under the program control, and getting a material mass

-temperature relation curve under the program control, namely the thermo-gravimetric curves. In

order to make the curves clear, adjust the curves with a proper offset.

Advanced Materials Research Vols. 821-822 57

0 100 200 300 400 500 600

0

20

40

60

80

100

120

140

W/%

T/oC

f-5

f-4

f-1

f-2

f-3

Fig.2 TG curve of the five fibers (offset=10)

By above TG curves it can be seen from Fig.2: First of all, the decomposition temperature of

cotton is lower than the rest of the four kinds of polyester fiber. Decomposition temperature of the

ordinary polyester is highest, this is because of their high crystalline and ordered molecular

arrangement. Decomposition temperature: f-5<f-1<f-3<f-2<f-4.So the modified polyester material

have worse thermal stability than ordinary polyester.

Differential scanning calorimeter analysis is other thermal analysis technology. Now this paper

use it to test the melting behavior of new polyester fiber. In order to make the curves clear, adjust

the curves with a proper offset.

50 100 150 200 250 300

-10

-5

0

5

10

15

20

25

30

35

40

45

50

55

60

hea

t flow

/mw

T/oC

f-3

f-2

f-1

f-4

Fig.3 DSC curve of the polyester fibers (offset=12)

Table 5 Melting point of fibers from DSC curve

f-1 f-2 f-3 f-4

Peak(melting point)/°C 239.99 216.05 233.44 249.13

Onset/°C 229.55 202.16 219.94 246.38

End/°C 246.71 221.46 238.71 252.11

58 Advances in Textile Engineering and Materials III

From Fig.3 and Table 5, it can be seen that the melting point of f-4 is 249.13°C, which is

obviously higher than other 3 modified polyester fibers, indicating the thermal stability of polyester

fibers degraded after modification[3]. That is, the modified polyester fibers are more

thermal-sensitive, and the heat treatment temperature of modified polyester fibers should be

controlled more carefully than ordinary polyester fibers in the textile processing[4].

Conclusions

The experimental results show that:

(1) The cross-section of f-1 is hollow, that of f-2 is circular, and f-3 with a triangular cross-section.

The non-circular cross section of f-1 and f-3 would be helpful to improve the hand, heat

retention and luster of textiles.

(2) The crystallinity of modified polyester fibers are less than that of ordinary polyester and cotton

fiber. This will help to improve the moisture absorption and dyeability of the fibers. And the

moisture regain of the modified polyester fiber is higher than that of ordinary polyester fiber,

but much less than that of cotton fiber.

(3) The mechanical properties of the modified fibers are worse than that of the ordinary polyester,

but much better than cotton fiber, except f-3. The modulus of 3 modified polyester fibers are

smaller than that of ordinary polyester fiber, but larger than that of cotton fiber. In general, from

the angle of tensile properties of f-3 and f-1 are more “cotton-like” than f-2 and f-4.

(4) The modified polyester fibers are more thermal-sensitive than ordinary polyester fiber. So the

heat treatment temperature of modified polyester fibers in the textile processing should be

controlled more carefully than ordinary polyester fibers[5].

Acknowledgements

This work was financially supported by the National Key Technology Support Program

(2011BAE05B00).

References

[1]Huaping Wang. Textile and Apparel Weekly. Vol.6 (2001), p. 1

[2]Mingyi Wang. China Textile Leader. Vol.2 (2011), p.26

[3]Yangchun Ou, Liqun Wu. Several kinds of chemical fiber thermal contrast. Chemical fiber, vol.

9 (2012), p. 28-30

[4]Changfei Fu, Chen bin. Study on fiber properties. (2011), p.15

[5]Gaofu Wei, Weihong Zhong. Synthetic Technology and Application, Vol.11 (2) (1996), p. 1-6.

Advanced Materials Research Vols. 821-822 59

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