Effects of vacuum steaming processes on the properties of continuous and staple polyester yarns

Abstract

In this study, the effects of vacuum steaming process parameters on physical properties, tensile properties and twist liveliness values of spun and filament 100% polyester yarns were investigated. For this purpose, yarns having different twisting coefficients and different numbers were twisted, and afterwards they were exposed to vacuum steaming at different temperatures and for different durations.

Linear density, hairiness, unevenness values, tensile properties and twist liveliness of these yarns were measured before and after vacuum steaming. The results obtained were assessed by means of COSTAT and SPSS statistical analysis programs and variation analysis, and Student–Newman–Keuls tests were carried out at 5% (0.05) level of significance.

The results of this study indicate that the effects of vacuum steaming temperature and duration on tensile properties, unevenness, hairiness and twist liveliness of spun polyester yarns, and tensile properties and twist liveliness of filament polyester yarns, are statistically significant.

Keywords

vacuum steaming tensile hairiness twist liveliness yarn polyester

Synthetic fibers are widely used today in the manufacturing of garments, upholstery fabrics and technical fabrics due to their advantages, such as high tensile values, high abrasion resistance and good fabric handle and low cost. Polyester (PES) fibers, a kind of synthetic fibers, are widely preferred to be used as filament yarns or spun yarns blended with natural fibers because of their properties, such as high tensile, easy-care properties and high fastness values.

Prior to the processes, such as weaving, knitting, dyeing and so on, spun and filament PES yarn twists must be subjected to heat setting in order to increase the yarn resistance against snarling and untwisting. Yarn relaxation occurs after the heat setting process of the yarn twist, thereby making it possible to avoid or minimize the yarn twist liveliness, which is yarn snarling and kinking behavior stemming from the tension in the yarn.

Yarn twist liveliness causes several problems in the subsequent processes, such as weaving, knitting, dyeing and so on. Skewness in woven fabrics, spirality in knitted fabrics, yarn breakages during weaving and knitting processes, bobbin deformation during dyeing, and color variations in the fabrics produced from the dyed yarns are some of these problems (www.welker.de).^1–5

Heat setting and relaxation processes, which are applied to PES and all other kinds of yarns, can be realized by giving certain tension to the twisted yarn wound on the bobbin under conventional storage conditions;⁵ however, this is a long process and does not advance homogeneously. For all these reasons, today these processes are carried out on vacuum steaming machines and are called vacuum steaming processes (www.welker.de).^1,3,6

Vacuum steaming processes that are applied to yarns show differences, depending on the properties that yarns are required to gain. These processes include conditioning performed to moisten the yarn (applied to cotton and natural yarns), relaxation processes carried out to decrease the yarn tension (applied to synthetic and high twist yarns), heat setting performed to fix the twist given to the yarn (applied to filament and spun synthetic yarns) and the pre-shrinking process (applied to the synthetic fibers). Since all these processes are carried out at a low temperature in a vacuum environment, every part of the bobbin is provided with uniform moisture distribution (www.welker.de).^1,3,6

PES yarns have structurally hydrophobic characteristics; that is, they absorb a very small amount of water; however, the changes that occur in the macromolecular structures of the fibers because of the saturated steam and temperature employed during heat setting in a vacuum steaming environment lead to changes in the physical and chemical properties of fibers.⁷ In textile products fibers are not available alone, and since yarns are formed by bringing fibers together and textile surfaces are formed by bringing yarns together, the changes that occur in fibers affect the physical and chemical properties of yarns and fabrics.

The objective of this study is to investigate the changes that occur in the tensile and physical properties of the spun and filament PES yarns after vacuum steaming performed at different temperatures and for different durations.

A review of the studies on vacuum steaming in the textile literature revealed that most of them were concerned with the conditioning of cotton yarns, because moisture brings about positive changes in the tensile properties of cotton yarns.^8–10

Also, the changes that occurred in tensile, physical and dye intake properties of PES/viscose blended and nylon 6 yarns after vacuum steaming were investigated,^6,11 and the effects of vacuum steaming methods on tensile and physical properties of cotton and viscose yarns were studied.¹² In addition, the effect of twist setting on yarn liveliness and 45% wool/55% PES woven fabric skewness was studied.¹³ However, as noted in the literature review, the number of studies about the effects of vacuum steaming on yarn properties is limited, and the studies performed with synthetic yarns are fewer in number; therefore, we think that our study on the changes taking place in the tensile, hairiness, unevenness and twist liveliness properties of spun and filament yarns after vacuum steaming will make a contribution to the literature.

Material and method

In this study, 37 and 20 tex spun PES yarns and 111, 167 and 300 dtex filament PES yarns were used. Twist coefficients of α _t = 38, α _t = 48 and α _t = 67 were used for spun yarns, and twist values of 400, 600 and 800 tpm were used for filament yarns.

The fineness and length of the spun PES fibers used were 1.2 denier and 38 mm respectively. The properties of the PES yarns used and the vacuum steaming process parameters applied to these yarns are given in Table 1.¹

Table 1.

The properties of polyester yarns and vacuum steaming process parameters.¹

Yarn number	Twist	Vacuum steaming temperature (℃)	Vacuum steaming duration (minutes)
37 tex,	α _t = 38,	90℃	40
20 tex	α _t = 48,	100℃	50
(spun yarn)	α _t = 67	110℃	60
111 dtex,	400 turns/meter,	90℃	30
167 dtex,	600 turns/meter,	100℃	45
300 dtex	800 turns/meter	110℃	60
(filament yarn)		120℃

Spun yarns were subjected to vacuum steaming on Obem (Italia), a vacuum steaming machine that works on the direct method and provides 75% vacuuming. Filament yarns were subjected to vacuum steaming on Text Mak-DEMOR, a vacuum steaming machine that runs on the indirect method and provides 75% vacuuming.

The physical (hairiness, unevenness values) and tensile properties and twist liveliness of the yarns were measured after the yarns were conditioned for 24 hours under standard atmospheric conditioning (20 ± 2℃ and 65% ± 2 humidity). All the measurements were taken before and after vacuum steaming.¹

The measurements of yarn linear density were made according to EN ISO 2060¹⁴ and tensile tests of the yarns were performed using Uster Tensorapid equipment EN ISO 2062.¹⁵ Hairiness values of the yarns were measured through the Uster Tester III equipment at a speed of 400 m/min. Twist liveliness values of the yarns were measured on a Keissokki Kringel Factor Meter. Five measurements of twist liveliness were taken for each yarn and the values obtained were expressed as Kr. Measurements of twist liveliness values of yarns have been made according to instruction manual no. 507-70011 of Kringel Factor Meter testing equipment.¹⁶

The effect of vacuum steaming temperature and time on the physical properties, tensile properties and twist liveliness of the PES yarns were evaluated by means of SPSS and COSTAT statistic programs, using variance analysis and the SNK (Student–Newman–Keuls) test at 5% (0.05) level of significance, five different values being entered for each parameter in the variance analysis.¹

Results and discussion

All the factors affecting physical properties, tensile, hairiness and twist liveliness of spun and filament PES yarns were investigated by means of the tables, which give the SNK test results and percentage changes.

Effects of vacuum steaming on tensile properties of spun polyester yarns

The SNK results given in Table 2 indicate that the effect of the twist coefficient on the yarn tensile property is statistically significant and the average breaking force and breaking tenacity decrease as the twist coefficient increases. It is known that tensile values of yarns increase up to the optimum twist point and begin to decrease after that point.^17–19 The decreases that take place in tensile values of 37 and 20 tex PES yarns with twist coefficient values over α _t = 38 result from using twist values over the optimum points.

Table 2.

Student–Newman–Keuls test results of spun polyester yarns.¹

	Mean breaking force (kN)		Breaking tenacity (N/tex)		Mean elongation at break (%)		Young’s modulus (N/tex)		Work of rupture (J)
Factor	37 tex	20 tex	37 tex	20 tex	37 tex	20 tex	37 tex	20 tex	37 tex	20 tex
Twist coefficient
α _t = 38	0.0146 (3)	0.0074 (3)	0.3833 (3)	0.3611 (3)	0.1568 (1)	0.1407 (1)	3.44 (3)	3.33 (3)	0.5002 (2)	0.2369 (2)
α _t = 48	0.0135 (2)	0.0069 (2)	0.3346 (2)	0.3278 (2)	0.1701 (2)	0.1493 (2)	2.75 (2)	2.88 (2)	0.4968 (2)	0.2304 (2)
α _t = 67	0.0091 (1)	0.0047 (1)	0.2062 (1)	0.1910 (1)	0.2117 (3)	0.1727 (3)	1.50 (1)	1.51 (1)	0.4103 (1)	0.1864 (1)
Vacuum steaming temperature
90℃	0.0122 (1)	0.0063 (1)	0.3074 (1)	0.2906 (1)	0.1780 (1)	0.1514 (1)	2.63 (2)	2.57 (1)(2)	0.4472 (1)	0.2115 (1)
100℃	0.0127 (2)	0.0063 (1)	0.3102 (1)	0.2966 (1)	0.1788 (1)	0.1533 (1)	2.54 (1)	2.63 (2)	0.4793 (2)	0.2143 (1)
110℃	0.0124 (1)(2)	0.0064 (1)	0.3064 (1)	0.2928 (1)	0.1817 (1)	0.1579 (2)	2.52 (1)	2.51 (1)	0.4808 (2)	0.2279 (2)
Vacuum steaming duration (min)
40	0.0127 (2)	0.0063 (1)	0.3109 (2)	0.2953 (2)	0.1823 (2)	0.1559 (2)	2.54 (1)	2.57 (1)	0.4825 (2)	0.2207 (2)
50	0.0125 (2)	0.0066 (2)	0.3135 (2)	0.3004 (2)	0.1789 (2)(1)	0.1592 (2)	2.59 (1)	2.59 (1)	0.4693 (2)(1)	0.2292 (2)
60	0.0121 (1)	0.0062 (1)	0.3000 (1)	0.2841 (1)	0.1773 (1)	0.1476 (1)	2.56 (1)	2.56 (1)	0.4555 (1)	0.2037 (1)

The values 1, 2, 3 in parentheses denote the effect of twist values, vacuum steaming temperature and vacuum steaming duration on the breaking load of the yarn, breaking tensile of yarn, breaking elongation of the yarn, Young’s modulus of the yarn and work of rupture of the yarn (3 denotes the highest rank and 1 the lowest rank).

Table 3 gives percentage changes in tensile properties of 37 and 20 tex PES yarns after vacuum steaming, and shows that tensile properties of 20 tex PES yarns increase while tensile values of 37 tex yarns decrease. The work of rupture values obtained indicate that the work of rupture values of 20 tex increase up to 112%; however, 37 tex yarns do not show such high increases. From this finding, it can be inferred that the vacuum steaming has given better results in thin yarns in terms of tensile values.

Table 3.

Changes in tensile properties of the spun polyester yarns after vacuum steaming (%).¹

	Vacuum steaming conditions		Changes at tensile properties of yarns (%)
			Mean breaking force		Breaking tenacity		Mean elongation at break		Young’s modulus		Work of rupture
Twist coefficient	Temperature (℃)	Duration (min)	37 tex	20 tex	37 tex	20 tex	37 tex	20 tex	37 tex	20 tex	37 tex	20 tex
α _t = 38	90	40	−0.76	24.27	1.36	25.19	4.00	24.05	−6.22	−1.00	4.28	40.83
		50	−2.97	24.63	3.53	24.74	2.45	22.56	13.88	−10.52	−0.85	40.25
		60	2.01	23.09	−2.51	30.57	3.95	25.57	−13.98	0.24	7.69	40.34
	100	40	9.68	13.34	11.05	25.74	14.61	15.34	−5.96	−2.14	23.17	21.04
		50	−6.97	19.88	−11.16	28.74	2.59	17.80	−3.32	−0.27	−4.98	29.11
		60	3.16	22.11	2.24	34.43	1.79	27.12	−3.97	5.27	12.46	39.47
	110	40	−9.04	25.71	−12.35	31.86	1.06	25.15	−5.28	−2.29	−5.47	42.71
		50	−5.34	63.32	−13.59	60.83	11.34	65.43	−23.16	−12.80	4.63	112.58
		60	7.00	23.97	13.05	28.71	19.66	26.88	−1.48	9.42	18.04	39.62
α _t = 48	90	40	−3.54	20.89	−4.83	34.63	2.76	21.65	−12.66	−3.86	−0.46	35.08
		50	−6.02	42.45	−0.26	48.84	0.79	34.87	−6.96	6.02	−2.76	63.09
		60	−0.58	−37.07	0.06	−31.20	6.06	−17.07	−8.70	17.88	6.16	−47.49
	100	40	−3.20	21.01	−5.70	37.94	7.64	21.52	−5.86	10.05	3.59	32.98
		50	−10.77	13.06	−12.83	18.96	−0.25	21.82	−6.58	2.49	−8.77	26.09
		60	8.15	16.30	−1.78	14.18	16.09	22.82	−32.25	−9.68	15.82	33.85
	110	40	−0.15	29.65	−5.49	30.61	2.16	34.14	−13.60	−9.70	10.10	54.88
		50	−0.15	9.71	−1.71	19.03	12.47	18.90	1.86	3.93	14.40	20.91
		60	4.88	37.24	13.00	44.25	16.68	39.12	−2.25	−7.41	22.37	61.06
α _t = 67	90	40	−10.52	56.67	−10.74	54.15	−21.58	13.31	−3.11	−12.58	−12.61	64.57
		50	−2.54	27.98	2.39	17.96	10.29	13.57	−4.80	−10.14	10.02	42.91
		60	3.18	19.26	1.53	12.49	5.49	9.11	0.00	1.24	12.33	21.60
	100	40	−13.48	27.92	−8.38	14.37	−4.33	19.40	5.11	−8.46	−10.58	41.01
		50	1.41	13.25	8.44	6.35	−0.77	18.58	0.42	−5.82	10.05	18.01
		60	−4.88	12.06	−7.09	5.61	−18.44	21.19	−6.47	−13.07	−22.94	24.54
	110	40	−0.85	13.34	−16.52	6.19	−24.34	24.95	−29.51	−17.13	−4.62	31.75
		50	−1.01	9.24	10.71	2.83	−10.27	14.14	8.23	−22.09	4.38	25.02
		60	−4.40	16.04	−0.81	4.40	−9.00	28.97	−3.75	−8.84	0.83	37.29

Raising the vacuum steaming temperature from 90℃ to 110℃ is not statistically significant for 37 and 20 tex yarns in terms of breaking tenacity, mean breaking force and mean elongation at break values, but it is statistically significant in terms of elasticity modulus and work of rupture values (Table 2). The elasticity modulus, which indicates the resistance of yarns against elongation, has decreased because of raised temperature and humidities, which is an expected consequence.²⁰ Increasing the temperature has not provided spun yarns with any advantages in terms of tensile values, but it has increased their work of rupture values, which indicate their performances in the subsequent production stages.

According to the SNK test results given in Table 2, the best results in terms of work of rupture values for 37 and 20 tex yarns have been obtained at 100℃ and 110℃, respectively, indicating that the temperature to be applied to should be increased as the yarn gets thinner.

When Table 2 is analyzed, it is seen that the duration of vacuum steaming has a statistically significant effect on breaking tenacity, mean breaking force and work of rupture of spun PES yarns. Tensile values of 37 tex PES yarns reach the highest level after vacuum steaming for 40 and 50 minutes, and the highest values for 20 tex yarns are obtained after vacuum steaming for 50 minutes. Increasing the duration to 60 minutes has brought about no positive effects on tensile properties of either yarns. It has been found that a 50-minute vacuum steaming is sufficient for both yarns in terms of tensile properties.

Increases are observed in tensile values of thin yarns after vacuum steaming as the temperature and duration increase, and we think that this is because the existing high unevenness values of thin yarns²¹ decrease after vacuum steaming processes. It is known that the strength of a yarn is determined by the weakest place; thus, an increase in the unevenness would cause the yarn to exhibit lower strength.²¹

Effects of vacuum steaming on unevenness properties of spun PES yarns (Um, CVm) (mean linear irregularity, coefficient of variation of the yarn mass)

When the SNK test results given in Table 4 are analyzed, it is seen that the effects of twist coefficient, vacuum steaming temperature and duration on yarn unevenness values are statistically significant. Unevenness values increase as the twist coefficients increase.²¹

Table 4.

Student–Newman–Keuls test results of spun polyester yarns.¹

Factor	Um		CVm		Hairiness		Twist liveliness
Factor	37 tex	20 tex	37 tex	20 tex	37 tex	20 tex	37 tex	20 tex
Twist coefficient
α _t = 38	7.77 (1)	9.49 (1)	9.76 (1)	12.01 (1)	5.65 (3)	4.81 (3)	2.03 (1)	2.14 (1)
α _t = 48	8.03 (2)	9.50 (1)	10.11 (2)	12.40 (2)	4.78 (2)	4.15 (2)	2.29 (2)	2.22 (2)
α _t = 67	8.20 (3)	9.83 (2)	10.55 (3)	12.97 (3)	4.66 (1)	3.70 (1)	3.00 (3)	2.99 (3)
Vacuum steaming temperature
90℃	7.73 (1)	9.43 (1)	9.87 (1)	11.88 (1)	5.12 (2)	4.25 (2)	3.04 (3)	3.13 (3)
100℃	8.22 (3)	9.72 (2)	10.43 (3)	12.31 (2)	4.97 (1)	4.23 (2)	2.39 (2)	2.26 (2)
110℃	8.04 (2)	9.66 (2)	10.10 (2)	12.19 (2)	4.99 (1)	4.18 (1)	1.90 (1)	1.96 (1)
Vacuum steaming duration
40 min	7.90 (1)	9.48 (1)	9.87 (1)	11.97 (1)	5.06 (2)	4.24 (2)	2.43 (1)	2.35 (1)
50 min	7.96 (1)	9.44 (1)	10.43 (3)	11.90 (1)	5.07 (2)	4.18 (1)	2.39 (1)	2.53 (2)
60 min	8.13 (2)	9.90 (2)	10.10 (2)	12.51 (2)	4.95 (1)	4.24 (2)	2.50 (2)	2.47 (2)

The values 1, 2, 3 in parentheses denote the effect of twist values, vacuum steaming temperature and vacuum steaming duration on the Um value of the yarn, CVm of yarn, hairiness of the yarn and twist liveliness of the yarn (3 denotes the highest rank and 1 the lowest rank).

The percentage changes of spun yarns given in Table 5 show that Um and CVm values of the yarns with the twist coefficient of α _t = 67 have decreased as far as 44.18% and 62.41%, respectively, after vacuum steaming, that is, vacuum steaming at the appropriate temperature and for appropriate duration, especially in cases where yarns with high twist numbers are used, decreases the unevenness value of the yarn, which is an important quality parameter during the postproduction stages and the sale of the yarn. High unevenness values, especially for the high twist yarns (α _t = 67), decrease after vacuum steaming. This is ascribed to a reduction in the yarn snarling, which is interpreted as a yarn fault (unevenness) during the Uster test.¹²

Table 5.

Changes in physical properties of the spun polyester yarns after vacuum steaming (%).¹

Twist coefficient	Vacuum steaming conditions		Changes at physical properties of yarns (%)
	Temperature (℃)	Duration (min)	Um		CVm		Hairiness		Twist liveliness
	Temperature (℃)	Duration (min)	37 tex	20 tex	37 tex	20 tex	37 tex	20 tex	37 tex	20 tex
α _t = 38	90	40	0.13	−0.32	0.11	−1.27	−7.73	13.15	−57.26	−63.98
		50	−1.60	3.32	−1.27	2.98	−6.18	16.31	−70.37	−45.40
		60	0.84	2.66	1.25	1.59	−12.22	3.95	−68.77	−66.27
	100	40	2.96	2.58	3.73	3.38	−9.33	13.42	−68.00	−66.46
		50	2.27	4.04	2.55	1.53	−9.28	5.09	−72.43	−69.14
		60	22.66	0.32	22.35	0.59	−13.60	−5.46	−72.68	−77.13
	110	40	−0.53	3.45	−0.11	3.51	−5.64	13.35	−77.53	−80.90
		50	2.31	2.36	1.53	3.04	−10.55	5.38	−76.99	−77.45
		60	3.30	0.39	1.60	−0.23	−9.98	7.71	−76.82	−60.12
α _t = 48	90	40	−12.04	−13.97	−32.43	−28.80	−4.23	0.00	−58.22	−65.90
		50	−4.95	−5.85	−21.36	−21.05	−4.26	11.76	−52.22	−52.87
		60	−7.53	−8.05	−27.06	−23.69	−8.24	6.06	−57.63	−54.20
	100	40	−1.52	−5.53	−19.22	−20.73	−8.96	10.67	−74.59	−70.61
		50	−14.47	−10.23	−32.93	−23.49	−13.57	0.87	−68.89	−68.91
		60	−9.45	−3.72	−28.60	−17.50	−8.91	3.15	−69.53	−70.85
	110	40	−8.60	−7.86	−25.62	−23.93	−12.01	1.59	−78.81	−78.17
		50	−8.76	−11.62	−30.52	−26.00	−8.83	8.99	−80.23	−75.37
		60	−5.37	−3.40	−28.43	−17.45	−9.96	3.60	−72.22	−70.52
α _t = 67	90	40	−38.16	−31.25	−55.27	−51.60	−8.97	13.26	−56.50	−45.07
		50	−32.98	−27.45	−52.91	−49.17	−11.93	17.13	−60.49	−57.60
		60	−37.82	−27.21	−57.66	−48.99	−7.05	14.18	−49.21	−46.30
	100	40	−38.52	−31.62	−57.00	−52.47	−9.62	10.54	−60.10	−57.84
		50	−36.95	−35.87	−56.74	−54.23	−9.81	13.29	−61.40	−62.13
		60	−43.57	−34.91	−59.42	−54.17	−10.33	17.95	−61.39	−65.95
	110	40	−37.00	−31.25	−55.08	−51.59	−13.12	12.29	−75.37	−73.33
		50	−40.95	−32.46	−58.25	−51.44	−12.76	10.71	−68.37	−66.03
		60	−44.18	−33.38	−62.41	−48.21	−11.54	9.26	−67.00	−65.33

When the effects of vacuum steaming temperature and duration are investigated, it is seen that the lowest results are obtained after vacuum steaming at 90℃ for 40 minutes. Increasing vacuum steaming temperature and duration has provided no advantage for either yarn numbers.

Effects of vacuum steaming on hairiness properties of spun polyester yarns

According to the SNK test results given in Table 4, the effects of twist coefficient, vacuum steaming temperature and duration on hairiness values of spun PES yarns are statistically significant.

In this study, it has been noted that hairiness values of 37 and 20 tex yarns decrease as their twist coefficients increase, and it is known that hairiness decreases as the number of yarn twists increases.^21–23

Yarn hairiness is associated with the number of fiber ends that protrude from the yarn surface, and the changes that occur in the diameter and mechanical properties of the fiber directly or indirectly influence mechanical and physical properties of yarns and end use characteristics of textile materials.^7,12,21,24 The normal forces between the yarns and fibers within the yarn and frictional locking between the fibers will be reduced in proportion to the vacuum steaming. This will cause a change in the mechanical properties, thus leading to changes in yarn physical properties, such as yarn hairiness. In this study, it is seen that vacuum steaming at 100℃ for 60 minutes and 110℃ for 50 minutes gives the best results for 37 and 20 tex PES yarns, respectively, in terms of hairiness.²⁵

Effects of vacuum steaming on twist liveliness of spun polyester yarns

The SNK test results given in Table 4 indicate that the effects of the twist coefficient, vacuum steaming temperature and duration on twist liveliness values of spun PES yarns are statistically significant.

As the twist coefficients increase, the tension in the yarn increases during the twisting process, and this increased tension increases yarn twist liveliness values (Table 4).²

As can be seen in Table 4, twist liveliness values of spun PES yarns decrease as vacuum steaming temperature and duration increase. Percentage changes given in Table 5 show that the twist liveliness values of 37 and 20 tex PES yarns have decreased from between 45.07% and 80.90%.

Tensions that occur during the spinning create tensions inside the yarns, which result in untwisting, kinking and snarling of the yarns during unwinding. This situation is called twist liveliness of the yarn, and all the snarls that occur cause yarn breakages, skewness problems in woven fabrics and spirality problems in knitted fabrics during the subsequent processes, which decrease the quality of the fabrics (www.welker.de).^2,3,4,5

All the processes that employ moisture and temperature, such as heat setting, conditioning, shrinking, relaxation and vacuum steaming, are frequently used in order to eliminate or minimize the tension that occurs in textile materials at various stages of production. In this study, decreases from between 45.07% and 80.90% have been obtained in twist liveliness values by applying vacuum steaming at different temperatures and for different durations. These decreases in the twist liveliness values minimize the problems arising from high twist liveliness values, as a result of which higher quality production can be achieved.

Effects of vacuum steaming on tensile properties of filament polyester yarns

The SNK test results given in Table 6 show that the effects of yarn number, twist coefficient, vacuum steaming temperature and duration on the yarn tensile properties are statistically significant. Also, the analysis of the SNK test results given in Table 6 indicates that the mean breaking force, breaking tenacity, mean elongation at break and work of rupture of yarns increase as the yarn gets thicker. The increase observed in the tensile property of the yarn is expected because the load required to break the yarn increases as the yarn gets thicker.

Table 6.

Student–Newman–Keuls test results of filament polyester yarns.¹

Factor	Mean breaking force (cN)	Breaking tenacity (cN/tex)	Mean elongation at break (%)	Work of rupture (cN.cm)	Twist liveliness (Kr)
Yarn linear density (denier)
111 dtex	452.384 (1)	32.1108 (1)	35.7139 (1)	5326.47 (1)	0.3056 (1)
167dtex	611.231 (2)	33.8299 (2)	41.5002 (2)	8359.30 (2)	0.3533 (2)
300 dtex	1082.206 (3)	37.4209 (3)	45.1031 (3)	16,179.03 (3)	0.3894 (3)
Turns per meter
400 turns/meter	728.994 (3)	35.4299 (3)	39.7114 (1)	9980.82 (1)	0.2667 (1)
600 turns/meter	714.279 (2)	34.5435 (2)	40.5624 (2)	9897.62 (1)	0.3694 (2)
800 turns/meter	702.547 (1)	33.3882 (1)	42.0434 (3)	9986.36 (1)	0.4122 (3)
Vacuum steaming temperature (℃)
90℃	716.302 (2)	34.7651 (3)	40.2160 (1)	9972.53 (2)	0.4104 (3)
100℃	705.373 (1)	34.1247 (1)	40.1039 (1)	9736.10 (1)	0.2067 (1)
110℃	718.815 (2)(3)	34.5101 (2)	41.7944 (3)	10,215.40 (3)	0.3585 (2)
120℃	720.604 (3)	34.4156 (2)	40.9754 (2)	9895.70 (2)	0.4222 (3)
Vacuum steaming duration (min)
30 min	714.750 (2)	34.5253 (2)	40.6513 (1)	9925.02 (1)	0.3700 (2)
45 min	709.128 (1)	34.0879 (1)	41.0697 (2)	9927.47 (1)	0.3122 (1)
60 min	721.943 (3)	34.7484 (3)	40.5963 (1)	10,012.31 (1)	0.3661 (2)

The values 1, 2, 3 in parentheses denote the effect of twist values, vacuum steaming temperature and vacuum steaming duration on the breaking load of the yarn, breaking tensile of yarn, breaking elongation of the yarn, work of rupture of the yarn and twist liveliness of the yarn (3 denotes the highest rank and 1 the lowest rank).

When the effect of the number of yarn twists on the yarn tensile is taken into consideration (Table 6), it is seen that as the twist value increases and the mean breaking force and breaking tenacity decrease, but mean elongation at break increases. The increased number of yarn twists brings about no change in the work of rupture values of the yarns. Breaking tenacity of filament yarn is expected to decrease as its twisting value increases, because twisting is not necessary for the attainment of tensile strength; however, it is necessary for the achievement of satisfactory resistance to abrasion, fatigue or other types of damage associated with stresses.^1,2,6,26 In addition, with increasing twist count, mean elongation at break values also rise because when the yarn is twisted under tension, it is likely that most of this tension will be borne by stretching of the outer filaments in order to accommodate them more easily in longer paths near the outside of the twisted structure. If the filaments have good elastic recovery, then on removing the tension in the yarn, the outer filaments will contract and the center filaments will buckle. When this happens, the breaking extension of the yarn will increase.^2,6

When the effect of vacuum steaming temperature on the tensile properties of filament PES yarns has been investigated, it can be seen that the highest tensile values have been obtained after vacuum steaming at 90℃. The mechanical properties of yarns or fibers depend on polymer structure and the microstructural properties, as well as thermal treatments applied on yarns.^6,27 The effects of vacuum steaming, a kind of thermal treatment, are associated with a change in the crystalline morphology of the fiber. Therefore, as a result of vacuum steaming, very small, imperfect or irregular crystallites, which are present in crystal lattice of PES yarn (synthetic yarn), are likely to melt at a temperature much below the real melting points and larger, more perfect or more regular crystals are likely to grow.^1,6,28 Besides, when water is used during these thermal treatments (for example vacuum steaming), the melting temperature can fall significantly depending on the chemical energy of the water used in vacuum steaming.^6,29 Consequently, breaking tenacity of the PES yarns is expected to rise up to a temperature determined by the condition of the thermal process and later on it is expected to fall down to the normal level. In this study, maximum breaking tenacity values have been obtained after vacuum steaming at 90℃.

From the results concerning the effect of vacuum steaming duration on the yarn tensile properties in Table 6, it can be seen that the highest breaking tenacity, mean breaking force and work of rupture values have been obtained after vacuum steaming for 60 minutes.

The changes in yarn tensile properties after vacuum steaming are given in Table 7 and the analysis of these indicates that increases take place in mean breaking force, mean elongation at break and especially work of rupture values of the yarns twisted with 600 and 800 turns per meter. Increases of as much as 80% take place after vacuum steaming, especially in the work of rapture values of yarns twisted with 800 turns per meter, because vacuum steaming carried out at an appropriate temperature and for an appropriate duration decreases the tension resulting from high twist.

Table 7.

Changes in tensile properties of the polyester filament yarns after vacuum steaming (%).¹

Turns per meter	Vacuum steaming conditions		Mean breaking force			Breaking tenacity			Mean elongation at break			Work of rupture
Turns per meter	Temperature (℃)	Duration (min)	111 dtex	167 dtex	300 dtex	111 dtex	167 dtex	300 dtex	111 dtex	167 dtex	300 dtex	111 dtex	167 dtex	300 dtex
400	90	30	−1.61	−4.39	1.57	−5.44	−9.18	−3.27	16.15	8.88	16.38	5.42	−1.62	11.33
		45	−1.52	−1.38	3.32	−5.76	−5.92	−1.66	16.12	6.77	18.99	5.05	0.42	15.33
		60	3.56	−0.92	4.70	−1.25	−11.08	0.72	30.04	11.39	12.95	24.72	4.53	12.53
	100	30	−0.64	0.45	0.28	−5.96	−4.44	−3.33	9.94	6.13	3.82	−1.34	1.43	−1.27
		45	−6.63	−4.36	0.55	−11.22	−10.09	−3.96	10.12	8.83	10.45	−8.46	−2.31	4.47
		60	−1.26	−5.48	1.48	−6.46	−10.17	−3.85	19.13	−0.75	16.82	6.97	−11.84	12.27
	110	30	0.35	−1.19	3.41	−6.28	−6.48	−2.78	19.92	7.01	11.27	7.41	−0.88	7.07
		45	−0.33	−1.10	−2.12	−7.91	−6.96	−9.01	39.77	15.68	16.64	22.24	7.05	7.87
		60	2.76	3.50	6.00	−3.54	−2.09	0.00	24.55	10.93	14.22	14.34	8.34	13.60
	120	30	−0.40	−0.94	0.74	−8.85	−8.25	−5.83	24.34	8.53	8.18	9.95	−0.18	1.07
		45	2.05	−0.32	0.18	−4.54	−7.12	−6.40	37.87	14.48	12.36	25.97	6.43	4.53
		60	4.70	0.65	2.77	−2.52	−6.48	−3.53	30.40	11.89	0.93	23.04	5.23	−3.07
600	90	30	8.69	−2.13	5.89	4.19	−6.17	−1.89	29.09	3.02	31.50	31.01	−3.76	24.69
		45	5.86	−3.52	10.59	1.00	−9.02	4.91	31.11	13.68	24.21	28.58	3.04	26.31
		60	0.52	0.98	9.49	−4.35	−4.68	1.86	9.78	15.30	26.44	3.00	10.12	25.23
	100	30	7.95	2.77	7.99	2.38	−1.80	0.50	32.47	15.11	31.64	31.20	11.79	29.08
		45	4.72	−3.35	5.39	0.32	−9.38	−1.77	32.61	12.31	21.27	27.14	1.51	15.38
		60	7.38	−1.20	5.89	1.24	−6.45	−0.99	32.36	12.09	20.06	31.03	4.05	23.08
	110	30	6.38	−1.14	8.29	0.05	−6.48	−0.71	25.80	8.48	33.62	21.00	−0.69	29.92
		45	7.64	−2.56	8.49	1.40	−8.22	0.53	34.74	12.15	28.64	31.51	1.56	25.69
		60	10.56	1.77	9.39	4.16	−3.79	1.86	32.03	5.18	21.16	32.97	0.75	19.85
	120	30	9.83	−0.80	5.69	3.03	−7.03	−3.32	40.34	8.61	30.71	38.80	0.62	25.46
		45	4.98	1.48	7.89	−2.24	−5.62	−2.42	28.80	9.77	31.95	20.18	4.17	26.00
		60	9.97	0.20	6.59	2.57	−6.37	−1.30	33.97	14.49	13.16	33.12	6.95	7.85
800	90	30	6.83	5.58	7.74	1.18	0.96	3.75	67.77	25.40	38.86	61.41	23.59	41.41
		45	6.42	2.15	5.82	1.21	−2.27	1.61	55.91	26.62	31.12	49.09	19.80	31.42
		60	7.03	5.13	7.84	1.10	−0.48	3.46	62.71	35.15	34.12	56.94	30.90	37.15
	100	30	7.03	4.73	3.80	0.11	−0.24	−2.37	69.89	28.49	34.36	62.94	24.86	31.08
		45	6.38	7.07	4.51	0.66	2.00	−0.92	67.86	33.11	38.26	65.41	32.22	35.94
		60	4.81	2.34	4.51	−1.40	−2.84	−0.92	60.92	32.77	38.26	50.10	25.13	35.94
	110	30	6.35	5.70	3.70	−1.48	−0.75	−3.29	57.56	38.64	43.78	47.00	33.33	38.37
		45	8.06	1.39	2.69	−0.30	−5.08	−4.51	74.11	32.33	52.35	63.95	22.18	45.23
		60	11.24	4.56	10.27	1.89	−2.18	4.02	90.90	38.11	48.91	84.96	32.54	54.86
	120	30	11.65	6.97	7.34	2.66	−0.12	0.23	84.55	37.61	37.72	80.90	31.69	37.24
		45	9.34	1.99	7.54	0.55	−4.69	1.25	63.08	29.46	36.64	54.70	20.16	36.81
		60	10.64	7.66	9.97	1.81	0.06	3.16	77.01	33.77	39.34	72.64	30.64	42.62

Effects of vacuum steaming on twist liveliness values of filament polyester yarns

The SNK test results given in Table 6 indicate that yarn number, the number of twists, vacuum steaming temperature and vacuum steaming duration have a statistically significant effect on yarn twist liveliness values.

From Figure 1, it can be seen that the thicker the filament PES yarns get, the higher their twist liveliness values are. As the yarns with the same twist coefficient get thicker, the torque generated in them during twisting increases. Thus, tensions capable of producing kinks and snarls in yarns are greater.^2,20,30

Figure 1.

Average twist liveliness values for filament polyester yarns before vacuum steaming.¹

The diagrams in Figure 1 show that, as the number of turns/meter of filament PES yarns increase, their twist liveliness values increase as well. The lowest values are obtained at 400 turns per meter, whereas the highest ones are obtained at 800 turns per meter. Since the yarn tension rises as the twist coefficient of the yarn increases, twist liveliness of the yarns is expected to increase. Hence, as the amount of twist in filament yarns increases, the twist liveliness values of these yarns increase as well.⁷

According to Table 6, vacuum steaming performed at 100℃ gives the most optimum results for the filament PES yarns in terms of twist liveliness values, thereby avoiding or minimizing twist liveliness-related problems during the subsequent processes. The effects of vacuum steaming, a kind of thermal treatment, are associated with a change in the crystalline morphology of the fiber.^6,7,27,28 Therefore, as a result of vacuum steaming, twist liveliness values of filament PES yarns increase when the temperature is increased over 100℃ due to the changes taking place in the internal structure of fibers.

When the effect of vacuum steaming duration is taken into consideration (Tables 6), subjecting filament PES yarns to vacuum steaming for 45 minutes is seen to be sufficient in terms of low twist liveliness values. Vacuum steaming for 60 minutes has not provided any advantages for PES yarns.

As can be seen from Table 8, twist liveliness values of filament PES yarns have decreased from between 85.52% and 100% after vacuum steaming processes due to the fact that the role of the twisting in filament yarns is different from that in the spun yarns. When a number of filaments in a continuous strand are twisted, radial forces develop, which in turn affect the relative position of the filaments in the yarn structure, leading to a close packing of all filaments in a given cross-section. Thus, the insertion of twist in yarns affects, in addition to tensile properties, the diameter and specific volume (in other words, softness or hardness) of yarns. The change in fiber packing in turn determines the cover of a fabric and such other properties as warmth, crease recovery, permeability and various other related characteristics.¹⁸ Besides, a large part of the twisting tension in filament yarns is taken up in stretching the outer filaments to acommodate them more easily along the longer paths near the surface of the twisted yarn. After releasing the tension in the yarn, the outer filaments will contract, causing the center filaments to buckle. For these reasons, the tension that occurs during twisting causes different effects on filament yarns compared to spun yarns, and the decreases observed after vacuum steaming in the twist liveliness values of filament yarns are higher than those observed in the twist liveliness values of spun yarns.

Table 8.

Changes in twist liveliness of the filament polyester yarns after vacuum steaming.¹

Turns/ meter	Vacuum steaming temp. (℃)	Vacuum steaming duration (min)	Changes in Kr value (%)
Turns/ meter	Vacuum steaming temp. (℃)	Vacuum steaming duration (min)	111 dtex	167 dtex	300 dtex
400	90℃	30	−92.79	−95.97	−88.89
		45	−90.99	−92.74	−90.37
		60	−91.89	−93.55	−96.30
	100℃	30	−95.50	−95.97	−95.56
		45	−95.50	−95.97	−100.00
		60	−92.79	−100.00	−100.00
	110℃	30	−96.40	−96.77	−88.15
		45	−95.50	−95.16	−93.33
		60	−95.50	−94.35	−95.56
	120℃	30	−94.59	−91.94	−94.81
		45	−95.50	−95.97	−96.30
		60	−95.50	−94.35	−91.11
600	90℃	30	−96.06	−91.91	−96.61
		45	−90.55	−86.76	−95.25
		60	−96.06	−93.38	−89.83
	100℃	30	−92.91	−97.06	−93.90
		45	−96.06	−96.32	−96.61
		60	−94.49	−95.59	−94.92
	110℃	30	−92.13	−97.06	−95.93
		45	−93.70	−96.32	−91.86
		60	−88.98	−89.71	−91.19
	120℃	30	−94.49	−86.76	−91.86
		45	−96.06	−96.32	−87.80
		60	−92.13	−91.18	−90.51
800	90℃	30	−94.62	−91.72	−91.19
		45	−90.00	−93.79	−92.45
		60	−93.85	−88.97	−89.31
	100℃	30	−96.92	−95.86	−93.08
		45	−95.38	−96.55	−96.23
		60	−100.00	−95.17	−96.86
	110℃	30	−92.31	−92.41	−91.82
		45	−93.85	−91.72	−96.23
		60	−92.31	−93.79	−91.19
	120℃	30	−88.46	−86.21	−89.31
		45	−95.38	−92.41	−96.86
		60	−88.46	−85.52	−92.45

Conclusion

The following results have been obtained from this study, which aims to investigate the effects of vacuum steaming on the tensile, physical properties of spun and filament yarns we have used.

Increases in tensile properties of 20 tex PES yarns occur, while decreases in tensile values of 37 tex yarns take place after vacuum steaming, that is, vacuum steaming has given better results in thin yarns in terms of tensile values.

Increasing the temperature has not provided spun yarns with any advantages in terms of tensile values, but it has increased their work of rupture values, which indicate their performances in the subsequent production stages.

Tensile values of 37 tex PES yarns reach the highest level after vacuum steaming for 40 minutes, while the highest values for 20 tex yarns are obtained after vacuum steaming for 50 minutes, which indicates that vacuum steaming durations need to be increased in order to obtain high tensile values in thin yarns.

It is seen that the lowest unevenness values of spun PES yarns are obtained after vacuum steaming at 90℃ for 40 minutes. Increasing vacuum steaming temperature and duration has provided no advantage for spun PES yarns in terms of unevenness, but in particular unevenness values of spun PES yarns with a high twist coefficient (α _t = 6 7) have decreased as far as 44.18% (Um) and 62.41% (CVm) after vacuum steaming.

The highest tensile values of filament PES yarns have been obtained after vacuum steaming at 90℃. The highest breaking tenacity, mean breaking force and work of rupture values of filament PES yarns have been obtained after vacuum steaming for 60 minutes.

Vacuum steaming performed at 100℃ for 45 minutes gives the most optimum results for the filament PES yarns in terms of twist liveliness values, thereby avoiding or minimizing twist liveliness-related problems during the subsequent processes.

Twist liveliness values of filament PES yarns have decreased from between 85.52% and 100% after vacuum steaming processes, but twist liveliness values of 37 and 20 tex PES yarns have decreased from between 45.07% and 80.90% after vacuum steaming. The tension that occurs during twisting causes different effects on filament yarns compared to spun yarns, and the decreases observed after vacuum steaming in the twist liveliness values of filament yarns are higher than those observed in the twist liveliness values of spun yarns.

Today in textile plants, very high temperatures and long durations are employed on steaming machines without considering properties of yarns, which causes unnecessary damage to the yarns and increases the energy cost. All these problems can be avoided by analyzing all the properties of the yarns (number, tensile, unevenness, hairiness, twist) before vacuum steaming, and preparing recipes for the temperature and duration to be applied to in the laboratory environment according to the optimum values required for these properties.

Footnotes

Funding

This work was supported by Apolteks Textile San. Tic. A.Ş and Epiriler Textile san. Tic. A.Ş.

References

Ş ardağ, S. A. Study about vacuum steaming processes of yarns and their effects on yarn properties. Doctorate Thesis, Uludağ University, Bursa, 2008, pp.1,95,105–109,158–160,192–194.

Hearle

JWS

Grosberg

Backer

. Structural mechanics of fibres, yarns, and fabrics, New York: Wiley-Interscience, 1977, pp. 31,32,64,69,235–31,32,64,69,235.

Portrait Xorella AG catalog. 2003.

Klein W. Man made fibres and their processing. Short spun spinning series. Volume 6, Manchester, UK: The Textile Institute, 1994, pp.12–13, 38–39.

Usenko V. Processing of man-made fibres. Translated from the Russian by Chernyshova N. Moscow: MIR Publishers, 1979, pp.178–189.

Ş ardağ

Kanik

Özdemir

. The effect of vacuum steaming processes on physical and dyeability properties of polyamide 6 yarns. Text Res J 2010; 80: 1531–1539.

Warner

. Fibre science, Upper Saddle River, NJ: Prentice-Hall Inc, 1995, pp. 270–270.

Arindam B. Influence of conditioning on cotton yarn properties. Indian Text J (A selective CD version of India’s No 1 textile monthly) 2005; 116: 1–5.

Toggweiler

Gleich

Wanger

. Improved quality with contexxor conditioned cotton yarn. Melliand English 1995; 9: 154–155.

10.

Ş ardağ

Özdemir

Kanik

. The effects of vacuum steaming process parameters on tensile properties of cotton and viscose yarns. Tekstil ve Konfeksiyon 2011; 21: 343–348.

11.

Ş ardağ

Özdemir

Kara

. The effects of heat setting on the properties of polyester/ viscose blended yarns. Fibres Text East Eur 2007; 15: 50–53.

12.

Ş ardağ

Özdemir

. The effects of tandem and conventional vacuum steaming methods on the properties of yarns. Text Res J 2012; 82: 183–194.

13.

Yazdi AA. Woven fabric skewness and yarn twist. In: proceedings of the 2nd international Istanbul textile congress, 2004, pp.1–7 (CD-ROM).

14.

EN ISO 2060:1995. Textiles – yarn from packages – determination of linear density (mass per unit length) by the skein method.

15.

EN ISO 2062:1995. Textiles – yarn from packages – determination of single end breaking force and elongation at break.

16.

Kringel Factor Meter Instruction Manual Book. Keisokki Kogyo Co. Ltd, 507–70011, 2007, pp.1–2.

17.

Adanur

. Wellington Sears handbook of industrial textiles, Lancaster – Basel: Technomic Publishing Co. Inc, 1995, pp. 589–589.

18.

Goswami

Martindale

Scardino

. Textile yarns, Canada: Wiley-Interscience Publication, John Wiley & Sons, New York, London, Sydney, Toronto, printed in the United States of America, 1977, pp. 184–184.

19.

Joseph Marjory

. Essentials of textiles, Northridge, CA: California State University, 1976, pp. 12,40,143–12,40,143.

20.

Morton

Hearle

JWS

. Physical properties of textile fibres, Manchester: Textile Institute and Heinemann, 1975, pp. 127,292–127,292.

21.

Goswami

Martindale

Scardino

. Textile yarns, Toronto: Wiley- Interscience, 1977, pp. 25,97,111,172,173,202,221–25,97,111,172,173,202,221.

22.

Barella

. Yarn hairiness. Text Progr 1983; 13: 1–61.

23.

Barella

. Yarn hairiness of yarns. Text Progr 1993; 24: 1–49.

24.

Bona

. Physical methods of product and process control. Textile quality 1994, pp. 290–290.

25.

Hearle

JWS

Miles

LWC

. The setting of fibres and fabrics, Watford: Merrow Publishing Co. Ltd, 1971, pp. 175–175.

26.

Treloar

LRG

Riding

. Theory of the stress–strain properties of filament yarns. J Text Inst 1963; 54: 13,55–13,55.

27.

Vasanthan

. Effect of heat setting temperatures on tensile mechanical properties of polyamide fibres. Text Res J 2004; 74: 545–550.

28.

Statton WO. The setting of fibres and fabrics, synthetic fibres: structure and setting. Watford, England: Merrow Technical Library, 1971, pp.15,63–65,96,117–120.

29.

Tarakcıoglu

. Textile finishing and machinery III, Izmir: Aracılar Matbaa, 1986, pp. 414–416,464–465.

30.

Hunter

Cotton spinning technology. In: Gordon

Hsieh

Y-L

(eds). Cotton: Science and technology, Cambridge: The Textile Institute, Woodhead Publishing Limited, 2007, pp. 270,272–270,272.