Determination of Factors Affecting the Quality of Sized Cotton Yarn Using Screening Experimental Method

ABSTRACT

This research examines screening of the factors affecting cotton-sized yarn gain strength, elongation, stretch, size pick-up, and yarn abrasion resistance. The factors considered in this research are sizing machine parameters like sizing machine speed, squeezing roller pressure, warp yarn tension of various sizing machine zones, warp yarn twist, and viscosity of the size paste. Taguchi design with Minitab software has been used to design and analyze the results of the experiments. The study revealed that viscosity, yarn twist, sizing machine speed, and wet tension affected sized yarn gain strength significantly. Viscosity has maximum contribution to gain strength (34.57%) compared to other factors and has a positive effect on the gain strength of the sized yarn. For stretch percentage and the loss elongation of sized yarn, the wet tension is the most significant factor with 50.30% and 52.13% contribution respectively. Moreover, for the size pick-up and yarn abrasion resistance of sized yarn, the speed of the sizing machine is the most effective parameter with 44.45% and 56.29% contribution, respectively. The screening experimental result revealed the most significant factor that must be further optimized using response surface methods of experimental design.

摘要

本研究筛选了影响棉浆纱增强、伸长率、拉伸度、上浆率和耐磨性的因素. 本研究考虑的因素是浆纱机参数，如浆纱机速度、挤压辊压力、各浆纱机区域的经纱张力、经纱捻度和浆糊的粘度. 使用田口设计的Minitab软件对实验结果进行了设计和分析. 研究表明，粘度、纱线捻度、浆纱机转速和湿张力对浆纱增强有显著影响. 与其他因素相比，粘度对增强的贡献最大（34.57%），并且对上浆纱的增强有积极影响. 对于浆纱的拉伸率和损耗伸长率，湿张力是最显著的因素，其贡献率分别为50.30%和52.13%. 此外，对于上浆纱的上浆性能和耐磨性，浆纱机的速度是最有效的参数，其贡献率分别为44.45%和56.29%. 筛选实验结果揭示了最重要的因素，必须使用实验设计的响应面方法进行进一步优化.

KEYWORDS:

• Sized yarn quality
• screening experiment
• Taguchi design
• tension
• sizing machine parameters
• signal to noise ratio

关键词:

• 上浆纱线质量
• 筛选实验
• 田口设计
• 紧张
• 上浆机参数
• 信噪比

Introduction

In weaving process, warp yarns, which are prepared as warp beams, are subjected to a variety of forces. Warp yarns are passed over the back rest, then drawn through drop wires and healed eyes, causing friction. Furthermore, the reed’s beat up forces exerts friction to the yarn and the yarn becomes abraded. To minimize excessive breakage of warp yarns during weaving, warp threads should be sized to acquire strength and improve friction resistance qualities (Özdemir 2018). Sizing is done to achieve good yarns and reliability characteristics such as enhanced yarn quality, increased weaving efficiency, and a smooth fabric surface. Weaving is made more difficult by improper, inadequate, and excessive size. The yarn specifications used in the warp yarn define the number of size pick. Correct sizing ingredient selection, and improved process control in warp yarn sizing result in the optimum performance for sized yarns quality. Controlling the size process enhances the yarn’s abrasion resistance, strengthens the warp yarn, and reduces the hairiness of the warp yarn. It also Improves warp yarn smoothness, tenacity, and fatigue resistance to withstand the pressures of the weaving process improving the efficiency of weaving machines and ensuring optimum fabric quality in weaving (Gandhi 2020). The warp yarn is pulled taut in sizing. This tension causes some stretch in the yarn, reducing elongation after sizing. This is a disadvantage of the sizing process.

Warp yarn sizing procedures are grouped into four types based on their application methods: traditional wet sizing, solvent sizing, cold sizing, and hot melt sizing. A typical conventional sizing machine comprises five main components: a creel zone, a size zone with size box/es, a drying zone, a leasing/splitting zone, and a headstock zone. Controlling each zone of the size machine will decide the process’s quality and productivity. Size concentration, viscosity, weight and pressure of the squeeze rollers, temperature of the size box, throughput speed of the warp through the box, and warp sheet tension are the main factors that influence the quality of a good-sized yarn (Devare et al. 2016). Controlling these parameters, as well as improving the size pick, has a substantial impact on warp breakage and sizing cost.

Further analysis revealed that the sized yarn quality issue is caused by a range of sizing machine parameters, viscosity, yarn count, yarn twist, methods of spinning and other yarn quality parameters.

The level of yarn twist affects size pick-up because yarn with a lower level of twist is more open and absorbs more size than yarn with a higher level of twist. Kovaevi and Gordo (2009) studied the influence of yarn twist level on size pick-up, abrasion resistance, and the breaking force of yarn. According to the findings, the degree of twist affects size pick-up, abrasion resistance, and breaking force. Thus, yarn characteristics have a direct impact on the selection of sizing liquor recipes; for example, low-twist and coarse-count yarn could require a different size mixture than highly twisted and fine-count yarn for the characteristics that are required (Gandhi 2020).

Another characteristic in the sizing process that must be controlled is the viscosity of a size paste. It indicates its resistance to the flow. The concentration (solid content) and temperature of the size paste have the greatest influence on its viscosity. The higher the concentration, the higher the viscosity. The viscosity of a size paste decreases as the temperature rises. The paste’s viscosity generally increases the wet pick-up by the warp sheet. It also controls the extent to which size paste penetrates the yarn structure. If greater penetration is desired, the viscosity should be reduced, and vice versa. Higher viscosity may be recommended for bulky yarns since penetration is relatively easier for bulky yarns (Singh and Verma 2016).

The wet pick-up of the warp sheet is also affected by the speed of sizing. According to some researchers, sizing machine speed has a substantial impact on size pick%, which grows as sizing machine speed increases, while others claim that higher sizing machine speed leads to low pick up%. Higher speeds minimize the yarn’s residence time in the past, which could reduce wet pick-up. The other benefit of increased speed is that it minimizes the squeezing time of the yarn, which should boost wet pick-up (Singh and Verma 2016). According to Jia and Zhang (2010), the speed of the sizing machine determines the penetration and coating rate while all other sizing technology factors remain constant. When the size machine’s speed is high, the penetration rate is low and the coating rate is high; the outcome is adversarial. Jia and Zhang (2010) investigated the relation between coating rate (thickness of film) and squeezing pressure using Elastohydrodynamic lubrication theory. Equation 1(1) $\mathrm{H}=\mathrm{K}\ast [(\mathit{\eta }\ast \mathrm{V})0.7/(\mathrm{F}/\mathrm{L})0.13],$(1) expresses the relationship between the coating rate (film thickness) and the squeezing pressure.

(1) $\mathrm{H}=\mathrm{K}\ast [(\mathit{\eta }\ast \mathrm{V})0.7/(\mathrm{F}/\mathrm{L})0.13],$(1)

where H is the thickness of the film (the amount of coating), K is the coefficient of the elastic modulus of the squeezing roller, η is the size solution viscosity, V is the squeezing roller rotation speed, F: squeezing roller pressure, and L: squeezing roller width covered by yarn. Equation 1(1) $\mathrm{H}=\mathrm{K}\ast [(\mathit{\eta }\ast \mathrm{V})0.7/(\mathrm{F}/\mathrm{L})0.13],$(1) indicates that increasing the squeezing roller pressure increases yarn penetration while decreasing the coating rate while keeping all other parameters constant. On the contrary, the result will be an opponent.

Stretch is one of key parameter which must be controlled for good quality of the yarn. In the process of sizing, yarns receive a stretch between the creel and size box, between the size box and drying cylinders, between the drying cylinders and draw rolls, and between the draw rolls and final beam. During sizing the stretch in the creel zone (i.e. between the creel and size box), wet zone (i.e. between the size box and drying cylinders) & leasing zone (drying cylinders and draw rolls) are mainly responsible for loss in elongation. If stretch in different zones is not effectively regulated, it will increase warp breaks throughout the weaving process, reducing loom performance (Devare et al. 2016). Net stretch must be kept under control to protect the flexibility of the sized yarn. In the case of cotton yarn, for example, the net stretch should not exceed 1.5%. Applying uniform tension across the entire length of the beam and along the beam buildup is critical for better-sized warp quality. Uniform stretch is a direct result of uniform tension, which may be precisely regulated if the yarn property is known (Singh and Verma 2016).

In this research, screening experimental method is used to identify the most significant factor affecting the quality of sized yarn. Screening designs are an efficient way to evaluate a large number of process or design parameters (factors) in a limited number of experimental runs or trials (i.e. with limited resources and budget (Antony 2023).

This study altered size machine parameters such as sizing machine speed, squeezing roller pressure, creel zone warp yarn tension, wet zone warp yarn tension, leasing zone warp yarn tension, and twist level of 100% cotton rotor spun yarn. The key factors impacting sized yarn’s gain strength, size pick up, abrasion resistance, elongation, and stretch qualities are subsequently screened. The relative impact of each factors on the responses were not investigated so far to the best of researcher’s knowledge.

Material and method

Materials

The input material for this study was 16Ne, 100% cotton carded rotor spun yarn with two distinct twist values of 860 and 920 TPM. The yarn was spun on a Rieter rotor spinning machine (Rieter R923) at Bahir Dar Textile Share Company. All other input parameters were held constant during the yarn sample’s manufacturer. Table 1 shows unsized yarn properties used for sizing. The twist factor is also stated in the metric count system.

Table 1. Unsized cotton rotor spun yarn properties for 16Ne.

Yarn twist (TPM)	U (%)	Strength (cN/Tex)	Elongation at break (%)	Abrasion resistance (no of cycles)	Dry weight (g/100 m)
860	13.23	7.54	6.782	11.8	3.44
920	11.12	7.95	4.552	12.0	3.58

Methods

The research was conducted by varying sizing machine parameters such as viscosity of size paste (12 second and 15 second), twist of the warp yarn (860 TPM and 920 TPM), speed of sizing machine (35 mpm and 55 mpm), squeezing pressure of sizing machine (14 KN and 17 KN), creel zonal warp yarn tension (440 N and 510 N), wet zonal warp yarn tension (340 N and 420 N), and leasing zonal warp yarn tension (1310 N and 1460 N).The dependent variables are gain strength, elongation, stretch, size pick-up and abrasion resistance of the warp yarn. After selection of factors that affect the quality of sized yarn the upper and lower level of the factors were determined based on literatures survey, sizing machine manual, and current working condition of the sizing machine. A Karl Mayer-Rotal SRL-SMR-SP sizing machine was used to make samples of the sized yarn at Bahir Dar Textile Share Company. The sized yarn samples were conditioned at a relative humidity of 65 ± 2 and a temperature of 20 ± 2 for 24 hours. Ten replicates were taken for all studied yarn properties.

Experimental design and procedure using taguchi method

When there are multiple elements influencing the process, the Taguchi design requires the fewest number of experimental runs. As a result, this strategy saves time and manpower by analyzing the significant parameters in terms of their main effects rather than the interaction effects between the factors (Zhu et al. 2018). Orthogonal array experiments were used to identify and investigate the impact of process factors on machine or system performance (Karna and Sahai 2012). According to Hou et al. (2007a), Orthogonal Array (OA) specified numbers in a matrix with rows and columns.

Selections of orthogonal array and assigning the independent variables to each column

The L8 OA Taguchi design was chosen for this study. Viscosity (X1), twist level (X2), sizing machine speed (X3), squeezing roller pressure (X4), creel zonal warp yarn tension (X5), wet zonal warp yarn tension (X6), and leasing zonal warp yarn tension (X7) were all considered to be process parameters of sized yarn quality. Each factor was dealt with two levels. Minitab 20 software was used to design and analyze the experiments. The experimental set up of the seven factors each at two levels are shown in Table 3.

Table 2. S/N formula’s for the analysis of the experimental result (Freddi et al. 2019).

Cases	S/N ratio formulas	Use when the goal is to
Smaller is the better	$\mathit{S}/\mathit{N}=-10\mathit{lo}{g}_{10}1/\mathit{n}\sum _{\mathit{i}=1}^n{y}^2\mathit{i}$	Minimize the response
Nominal is the better	$\mathit{S}/\mathit{N}=-10{log}_{10}\frac{{\bar{\mathrm{y}}}^2}{S^2}$ $\mathit{where}:\bar{Y}=\frac{1}{n}\sum _{\mathit{i}=1}^n\mathit{yi}$ $S^2=\frac{1}{\mathit{n}-1}\sum _i^n{\left(yi-\bar{\mathrm{y}}\right)}^2$	Target the response and you want to base S/N ratio on means and standard deviations
Larger is the better	$\mathit{S}/\mathit{N}=-10\mathit{lo}{g}_{10}1/\mathit{n}\sum _{\mathit{i}=1}^{n}1/y^2\mathit{i}$	Maximize the response

Table 3. Experimental runs and average test results for each response.

L8(2^7) Orthogonal Array
Exp. run	Independent variables or factors							Response variables
	X1	X2	X3	X4	X5	X6	X7	Avg. Gain strength	Avg. Loss elongation	Size pick-up	Yarn abrasion resistance	Yarn stretch
	Sec	TPM	MPM	KN	N	N	N	%	%	%	No cycles	%
1	12	860	35	14	440	340	1310	34.74	18.88	11.42	20.0	1.1
2	12	860	35	17	510	420	1460	28.13	29.67	7.35	19.3	1.8
3	12	920	55	14	440	420	1460	14.22	22.75	11.45	13.0	1.6
4	12	920	55	17	510	340	1310	23.87	23.24	10.31	18.2	1.5
5	15	860	55	14	510	340	1460	31.15	22.92	16.37	15.2	1.4
6	15	860	55	17	440	420	1310	38.34	27.88	14.36	16.5	1.8
7	15	920	35	14	510	420	1310	30.43	24.165	9.72	18.1	1.4
8	15	920	35	17	440	340	1460	38.10	17.95	9.97	24.0	1.3

Characterizations of dependent variables/responses

Gain strength and loss of elongation

A universal tensile strength tester was used to examine the tensile properties of sized and unsized yarn. For each experiment, 10 replicates were taken, and the average value was used for analysis. The tensile strength and elongation properties of sized and unsized yarn were tested using ISO 2062 universal tensile strength tester (STATIMAT ME + tensile tester) (ISO 2062– 2062–2013). The gauge length and speed used were 500 mm and 300 mm/min respectively. To find the amount of gain strength and loss elongation due to the sizing process, equation 2(2) $\mathit{Gain}\mathit{strength}=\left(\frac{\mathit{sized}\mathit{yarn}\mathit{strength}-\mathit{unsized}\mathit{yarn}\mathit{strength}}{\mathit{unsized}\mathit{yarn}\mathit{strength}}\right)100$(2) & 3(3) $\mathit{Loss}\mathit{elongation}\mathrm{\%}=\left(\frac{\mathit{unsized}\mathit{yarn}\mathit{elongation}-\mathit{sized}\mathit{yarn}\mathit{elongation}}{\mathit{unsized}\mathit{sized}\mathit{yarn}\mathit{elongation}}\right)100$(3) were used (Wu et al. 2021).

(2) $\mathit{Gain}\mathit{strength}=\left(\frac{\mathit{sized}\mathit{yarn}\mathit{strength}-\mathit{unsized}\mathit{yarn}\mathit{strength}}{\mathit{unsized}\mathit{yarn}\mathit{strength}}\right)100$(2)

(3) $\mathit{Loss}\mathit{elongation}\mathrm{\%}=\left(\frac{\mathit{unsized}\mathit{yarn}\mathit{elongation}-\mathit{sized}\mathit{yarn}\mathit{elongation}}{\mathit{unsized}\mathit{sized}\mathit{yarn}\mathit{elongation}}\right)100$(3)

Stretch percentage

In the Karl-Mayer Rotal-SRL sizing machine, the stretch percentage is clearly shown on the control panel. Therefore, the value of sized yarn stretch% was obtained directly from the control panel for each experiment.

Yarn size pick-up

The gravimetric test and the desizing test are the two procedures for assessing size pick-up%. In this study, the size pick-up percentage was determined using the gravimetric test method. This approach is used to calculate the amount of size pick-up. However, there is no standard for it. The gravimetric method involves the following steps: drying the yarn samples to absolute dryness before sizing, weighing, air-conditioning, sizing, drying yarn samples to absolute dryness after sizing, and final weighing.

The dry weight of sized and unsized yarn was assessed in this study using an ETADRY (moisture testing oven) machine in accordance with ISO 6741. The steps were as follows: The initial 100-meter length of yarn was measured and weighted to determine its mass. The weighted samples were then placed in the canister that had been opened. Close the drying chamber lids, turn on the oven, and let it run for around 20 minutes at 105 ± 5°C. After that, turn off the oven and reweight the samples. Weighting was repeated at 5-minute intervals until there was no progressive weight change in the sample more than 0.05%. The final weight was reported as the sample’s dry weight. The amount of size pickup was determined using the formula stated in equation 4(4) $\mathit{size}\mathit{pick}\mathit{up}\mathrm{\%}=\left(\frac{\mathit{sized}\mathit{yarn}\mathit{dry}\mathit{weight}-\mathit{unsized}\mathit{yarn}\mathit{dry}\mathit{weight}}{\mathit{unsized}\mathit{yarn}\mathit{dry}\mathit{weight}}\right)100$(4) (Wu et al. 2021).

(4) $\mathit{size}\mathit{pick}\mathit{up}\mathrm{\%}=\left(\frac{\mathit{sized}\mathit{yarn}\mathit{dry}\mathit{weight}-\mathit{unsized}\mathit{yarn}\mathit{dry}\mathit{weight}}{\mathit{unsized}\mathit{yarn}\mathit{dry}\mathit{weight}}\right)100$(4)

Sized yarn abrasion resistance

The instrument is made up of two reciprocating bars, one of which is composed of hardened steel and the other with typical abrading substance. Yarns are threaded from the fixed holder to the flexible holder and clipped on. When the yarn breaks, the flexible holder collapses because the initial tension extended on each strand is 0.5. And the number of rubs for that specific sample was recorded in terms of cycles.

Analyzing of experimental data

Size pick up, yarn gain strength, abrasion resistance, stretch and elongation are measured. The outcome of the OA experiment is then analyzed to discover how much impact each component or parameter can contribute. The OA data are analyzed using an analysis of variance (ANOVA). The signal-to-noise (S/N) ratio was employed by taking parameter values into account for desired quality response and variation from the mean line. The signal-to-noise ratio was calculated and analyzed in three cases, depending on the criteria used for optimization of the quality characteristic as seen in Table 2.

Where y_i denotes the nth observation of the response variable, and ȳ²denotes the square of the mean and s² the variance of the observations of the replicated response values, n denotes the number of trials for the experiment. After determining the S/N ratio for each response, the rank was calculated by subtracting the minimum value from the maximum value or the converse based on the criteria required to optimize the response in each column, and the most effective input parameter was determined. When the parameter values are far from the mean line, then it is significant. The contribution values (%) were determined using the ANOVA table’s sum of squares values. The higher is this value on the output of the parameter, the more effective it is regarded to be at that rate.

Result and discussion

Evaluation of impact of independent variables on the sized yarn properties

Impact of independent variables on gain strength of sized yarn

The average test results for eight experimental runs of gain strength of sized yarns are shown in Table 3. The average results are then converted into signal to noise (S/N) to find the main effects for signal-to-noise ratio and means. The signal-to-noise ratio for the gain strength of the sized yarn was calculated based on the criteria that larger is better because the goal is to maximize the gain strength of the sized yarn. The ANOVA of the S/N ratio of gain strength is shown in Table 4, and the percentage contribution of each factor to the gain strength of the yarn is also calculated. The bigger value indicates the highest effect of the factor on the response. The viscosity of the size paste has the highest value followed by yarn twist level, sizing machine speed, wet zonal yarn tension, squeezing pressure, leasing zonal yarn tension. Whereas creel tension has the least effect for gain strength of sized yarn.

Table 4. Analysis of variance for signal to noise (S/N) ratio of gain strength.

Source	DF	Seq SS	Adj SS	Adj MS	% contribution
Viscosity	1	19.25	19.25	19.25	34.57%
Yarn twist	1	11.14	11.14	11.14	20.01%
Speed	1	9.96	9.96	9.96	17.88%
Squeezing pressure	1	5.15	5.15	5.15	9.26%
Creel tension	1	0.14	0.14	0.14	0.27%
Wet tension	1	5.25	5.25	5.25	9.43%
Leasing tension	1	4.77	4.77	4.77	8.58%
Residual Error	0	*	*	*
Total	7	55.69			100%

The effect of each sizing process parameter on the S/N ratio is calculated at different levels since the experiment is orthogonal.

Figure 1 presents the main effect of sizing process parameters on gain strength of sized yarn. As shown in the figure, an increase in gain strength of the sized yarn was observed with an increase in the viscosity of the paste and squeezing pressure. This is because high viscosity level allows for high take-up of the paste. This higher size pick-up leads to a higher size add-on of sized yarns; the more size add-on, the better the anchoring of fibers together and reduces inter fiber slippage. Therefore, this enhances gain strength of sized yarn. This is also supported by (Zhu, Zheng, and Li 2013).

Figure 1. Main effect plots of each factor on gain strength of sized yarn.

The second most effective factor for gain strength is yarn twist level. The gain strength of sized yarn is sensitive to variation in the level of yarn twist. From the graph in Figure 1, it is shown that the main effect of yarn twist level has an inverse relation with the gain strength of sized yarn. Highly twisted yarn is more compacted and resists size pick-up and reduces the penetration of sizing material into the yarn structure (Kovačević and Penava 2004). These also reduce the gain strength of sized yarn; therefore, the gain strength of the sized yarn reduces with the increase in yarn twist level.

The speed of the sizing machine ranked as the third parameter to influence the strength of sized yarn. The gain strength of the sized yarn reduced as the sizing speed increased, as indicated in Figure 1.

The high squeezing pressure allows more penetration of size paste within the yarn structure. This also enhances better inter-fiber binding and better anchorage of the size film and give the yarn a higher packing density or compactness. Therefore, it improves the strength of sized yarn; this is also in agreement with (Maatoug, Ladhari, and Sakli 2007a). The gain strength is not much affected by the squeezing roller pressure level change since the yarn used for this experiment is a coarser count. The size paste is also easily penetrated with low squeezing pressure for coarser yarns.

Tension zones, such as wet zonal yarn tension (WT), creel zonal tension (CT), and leasing zonal tension (LT), have an inverse effect on sized yarn strength, as shown in Figure 1. This is because yarn with a high wet tension has greater stretch and generates more fiber slippage in the yarn structure. This results in a decrease in gain strength and it is also supported by (Salama et al. 2021). Tension applied in the leasing zone and creel zone was ranked as six and seven, respectively, and did not have much effect on gain strength of the sized yarn. Because the increase in yarn length and the creation of fiber slippage in the dry state is less than in the wet state, leasing zonal tension variation has least influence on the gain strength of the yarn.

Impact of independent variables on loss elongation of sized yarn

The analysis of the signal-to-noise ratio and ANOVA were done to determine the rank of each input factor and their percentage contribution to the loss elongation of sized yarn.

The S/N ratio for loss elongation was analyzed based on the principle that the smaller the better since the goal of sizing is to minimize the loss elongation of sized yarn.

As illustrated in Figure 2, the loss of elongation of sized yarn increased with the rise in wet tension, creel tension, squeezing pressure, and speed of the sizing machine. However, a decreasing trend of loss elongation was observed with the rise of yarn twist level; the viscosity of the paste and leasing tension did not show deviation from the mean line and had the least effect on the loss elongation of the sized yarn.

Figure 2. Main effect plots of factors on loss elongation (a) and stretch% (b) of sized yarn.

When the amount of wet tension is increased, loss elongation deviates significantly from the mean line, and it accounts for the biggest contribution (52.13%) of the identified independent variables. This is owing to the fact that when the yarn is in a stretch position in the wet state, fiber to fiber attachment in the yarn structure became low, resulting in free movements of fiber and excessive elongation of the yarn in the wet state. The greater the yarn stretch, the larger the yarn elongation loss. It is also agreed with the previous study by (Devare et al. 2016).

However, the leasing tension and viscosity have no substantial effect on the sized yarn’s loss of elongation. Their contribution to loss elongation is 0.24% and 0.27% respectively (Table 5). This is because the stretch after the drying zone is not greater since the yarn recovers the majority of its original length; it is only used to obtain clean threads in the splitting zone without thread breaking. Previous works (Devare et al. 2016; Salama et al. 2021) provide support for this investigation.

Table 5. Analysis of variance for signal to noise (S/N) ration of loss elongation.

Source	DF	Seq SS	Adj SS	Adj MS	% contribution
Viscosity	1	0.04	0.041	0.041	0.27%
Yarn twist level	1	1.86	1.86	1.869	12.11%
Speed	1	1.02	1.025	1.025	6.63%
squeezing pressure	1	1.30	1.30	1.30	8.45%
Creel tension	1	3.12	3.12	3.12	20.17%
Wet tension	1	8.05	8.05	8.05	52.13%
Leasing tension	1	0.04	0.04	0.04	0.24%
Residual Error	0	*	*	*	100%
Total	7	15.44

Figure 3 depicts the effect of changing the twist level on lost elongation. The contribution percentage is 12.11%. When the level of yarn twist was reduced, the loss elongation of sized yarn raises Under all sizing settings, the largest size pick-up is obtained with the lowest twist level, and the lowest with the highest twist level, and this also agreed upon (Kovačević and Gordoš 2009). Obtaining a high size pick results in a more compacted structure in the sized yarn and does not allow free movement of fiber or fiber slippage in the yarn structure, according to Lord (2003). Whereas for high-twisted yarn, the size pick was dropped as it prevented sized particles from penetrating into the yarn structure (Kovačević and Gordoš 2009).

Figure 3. Main effect plots of each factor on size pick up% (a) and abrasion resistance (b) of warp yarn.

The squeezing pressure has an effect on the loss elongation of sized yarn. It contributes 8.45% among the selected independent factors. When the squeezing pressure varied from low to high levels, the loss of elongation of the sized yarn increased, as seen in Figure 2. This is because high squeezing pressure compresses the yarn structure, increasing its compactness and packing density, which increases cohesion and decreases fiber mobility and inter-fiber slippage. This reduces the elongation at break of the yarn, and the elongation loss becomes significant which is also agreed with the previous work by (Maatoug, Ladhari, and Sakli 2007b).

The speed of the sizing machine contributes 6.6% to loss elongation. When it increased, the loss elongation also increased. At the high speed of the sizing machine, higher size pick-up will result in higher size add-on of sized yarns; the more size add-on, the better the anchoring of fibers together and the reduction of inter-fiber slippage. This reduced the elongation of sized yarn and increased the loss of elongation in sized yarn. This investigation is supported by the idea of (Ayele and Abay 2023; Maatoug, Ladhari, and Sakli 2007b).

Impact of independent variables on stretch percentage of sized yarn

Table 6 shows the analysis of variance for the S/N ratio of eight experimental results of stretch percentage. Then the %-Contribution values for each sizing machine input parameter on stretch were calculated using the sum of squares values in Table 6. Among the seven factors, wet tension has the highest percentage contribution value of 50.30% followed by the squeezing roller pressure (23.65%). The speed of the sizing machine ranked third with 17.31% contribution and the fourth is creel tension, with 4.06% contribution. Leasing zone tension, yarn twist and viscosity contributed 3.46%, 1.14% and 0.08%, respectively.

Table 6. Analysis of variance for signal to noise (S/N) ratio of stretch%.

Source	DF	Seq SS	Adj SS	Adj MS	% contribution
Viscosity	1	0.01	0.012	0.012	0.08%
Yarn twist	1	0.17	0.167	0.167	1.14%
Speed	1	2.53	2.53	2.53	17.31%
Squeezing pressure	1	3.45	3.45	3.45	23.65%
Creel tension	1	0.59	0.59	0.59	4.06
Wet tension	1	7.34	7.34	7.34	50.30%
Leasing tension	1	0.50	0.51	0.51	3.46%
Residual Error	0	*	*	*
Total	7	14.60			100%

As shown in Figure 2, the stretch percentage of sized yarn increases with the rise in wet tension, squeezing roller pressure, sizing machine speed, creel zone yarn tension, and leasing zone yarn tension. However, it decreases with the rise of yarn twist level. The viscosity of the paste did not show a significant deviation from the mean line and had the least effect on the stretch percentage of sized yarn.

When the wet zone yarn tension level is changed, the stretch% of sized yarn deviates significantly from the mean line. Figure 2b shows how the stretch of the sized yarn grew dramatically when the wet zonal yarn tension increased from low to high. The reason for this is that when the yarn was in a stretch position in the wet state, fiber to fiber attachment in the yarn structure became low, resulting in free fiber movement and excessive wet yarn elongation. The aforementioned idea is compatible with the earlier investigation of (Narkhedkar, Kadole, and Patil 2014). When the level of squeezing pressure varied from low to high, the stretch of the sized yarn increased, as seen in Figure 2.

When the speed of the sizing machine increased, the stretch of the yarn also increased, as shown in Figure 2.

The twist level of warp yarn has less effect on the stretch of sized yarn because of the dual effect on the stretch of sized yarn. Low twisted yarn allows size material to penetrate into the yarn structure; this reduces inter-fiber slippage and reduces the stretch of sized yarn. On the other hand, high-twist yarn by itself is tightly plied and tends to be more elastic and stretch-resistant. The viscosity of size paste has no significant effect on the stretch of sized yarn.

Impact of independent variables on yarn size pick percentage

The size-pick of sized yarn was determined by the dry weight difference between sized samples and unsized yarn. Table 7 shows the analysis of variance for signal-to-noise (S/N) ratio of size pick-up%.

Table 7. Analysis of variance for signal to noise (S/N) ration of size pick- up (%).

Source	DF	Seq SS	Adj SS	Adj MS	% contribution
Viscosity	1	6.54	6.54	6.54	20.46
Twist	1	2.80	2.80	2.80	8.77
Speed	1	14.20	14.20	14.20	44.45
Squeezing p	1	3.99	3.99	3.99	12.51
CT	1	1.83	1.83	1.83	5.71
WT	1	2.28	2.28	2.28	7.15
LT	1	0.30	0.30	0.30	0.95
Residual error	0	*	*	*
Total	7	31.9516			100

The main effect plot for the mean of sizing parameters on yarn size pick up percentage is shown in Figure 3. The rise of viscosity and sizing machine speed increased the size pick of sized yarn. However, decreasing trend of size pick up was observed with the rise of wet tension, creel tension and squeezing pressure. The leasing tension did not show deviation from the mean line and has least effect on size pick of warp yarn.

As shown in Table 7, the sizing machine speed is the most significant factor, accounting for 44.45% for the size pick-up change of sized yarn. The size pick-up of the yarn rose as the sizing machine speed increased from low to high, as illustrated in Figure 3. This is due to the shorter squeezing period and reduced squeezing effect at higher speeds, which results in less size material removal from the yarn (Fernando and Jayawardana 2015; Turukmane, Gulhane, and Patil 2019). Increasing size pick-up with less squeezing time has a dominant effect over the waiting time of yarn in the size box; this is supported by previous work of (Ayele and Abay 2023).

The second most effective factor to influence the size pick of the warp yarn was the viscosity of the size paste; it contributed 20.46%. When the viscosity of the size paste increased, the size-pick of the warp yarn increased. This is due to the fact that when the viscosity of size solution increases, it will be easier for size solution to cover the surface of yarn when the yarn goes through size solution. Therefore, the coating rate of the yarn will be higher and the penetration rate will be low. This idea is also supported by (Jia and Zhang, 2010).

The contribution of squeezing roller pressure to the size pick-up variation of warp yarn is 12.51% and ranks as the third most affecting factor. This implies that the size pick-up of warp yarn is sensitive to the level change in squeezing roller pressure. As the squeezing roller pressure increased, the size pick-up of the warp sheet was reduced. This is because increased squeezing pressure allows for better penetration of size within the yarn structure while saturating with a little amount of size material and reducing the yarn’s absorptive capacity. In addition, high squeezing pressure removes excessive size material from the yarn, and this is supported by the former study (Ayele and Abay 2023; Kovačević and Gordoš 2009).

The wet zonal yarn tension contributes 7.15% to the size pick-up of the warp sheet. As the tension in the wet zone increase the size pick-up of the yarn decrease. This is due to the fact that, the length of the yarn in the wet state after sizing increase to some extent due to tension and as a result of this the amount of size material per unit length was reduced. The creel tension has less effect on the size pick-up of sized yarn. It contributes 5.71% to the size pick-up of the warp sheet. The increase in yarn tension during sizing reduced the size pick of the yarn for both creel zonal and wet zonal yarn tensions, as shown in Figure 3.

The yarn twist level effect for size pick-up of the warp yarn was ranked fourth, and it contributes 8.77% among the selected independent parameters. The relationship is shown in Figure 3. When the yarn twist level increase, the size pick-up decreased, and when the twist level decreases, the size pick-up of the yarn increases. The reason behind this is that high-twisted yarn has higher compactness, and packing density which doesn’t allow it to take more size material and penetrate too much size material easily unless the residence time is increased, This idea is agreement with (Turukmane, Gulhane, and Patil 2019).

Figure 3 shows that, sizing machine speed, viscosity of the paste, squeezing pressure, yarn twist level, possess variations with respect to the mean line. Whereas, wet tension and creel tension showed less deviation from the mean value. The leasing tension has almost no deviation from the mean line.

Impact of independent variables on yarn abrasion resistance

The analyses were done with the goal of the larger is better. The percent contribution of each independent variable to the yarn abrasion resistance of sized yarn was also determined in Table 8.

Table 8. ANOVA for signal to noise (S/N) ratio of yarn abrasion resistance.

Source	DF	Seq SS	Adj SS	Adj MS	% contribution
Viscosity	1	0.29	0.29	0.29	1.62%
Yarn twist	1	0.03	0.03	0.03	0.19%
Speed	1	10.17	10.17	10.17	56.29%
Squeezing pressure	1	4.17	4.17	4.17	23.07%
Creel tension	1	0.04	0.04	0.04	0.21%
Wet tension	1	3.08	3.08	3.08	17.08%
Leasing tension	1	0.28	0.28	0.28	1.54%
Residual Error	0	*	*	*
Total	7	18.08			100%

Table 8 shows that the most effective parameter was the speed of sizing machine, which contributes about 56.29% for abrasion resistance of sized yarn followed by squeezing roller pressure (23.07%), wet zone yarn tension (17.08%), viscosity (1.62%), leasing tension (1.54%), creel tension (0.21%) and twist level (0.21%). The graph in Figure 3 presents the main effect of sizing process parameters on the abrasion resistance of sized yarn.

As illustrated in the graph, an increase in the yarn abrasion resistance of sized yarn was observed with an increase in squeezing pressure, viscosity of size paste, and yarn twist level. However, a decreasing trend of sized yarn abrasion resistance was observed with the rise of sizing machine speed, wet tension, leasing tension, and creel tension.

The graph in Figure 3 demonstrates that as the sizing speed rose, the abrasion resistance of the yarn dropped. This is owing to the fact that at high sizing machine speeds, there is less squeezing time, which results in a high coating on the yarn surface, but the penetration rate is lowered. When the yarn is rubbed with the abrading material, the size material on the yarn surface is readily removed, which is also consistent with (Ayele and Abay 2023; Jia and Zhang, 2010). On the other hand as the squeezing roller pressure increased, the yarn’s abrasion resistance increased. This is because as the squeezing pressure increase penetration rate increase and provides better inter-fiber binding which improves the abrasion resistance of sized yarn, and it is also agreed with (Ayele and Abay 2023; Maatoug, Ladhari, and Sakli 2007b).

Furthermore, as the wet zonal yarn tension increased, so did the yarn abrasion resistance. The reason for this is, while the tension in the wet zone increase the yarn stretches highly and its length increased and the size material is shifted from the inner to the outside surface of the yarn. As a result, the yarn surface became easily rubbed, and the yarn breaks with the fewest number of cycles during abrading.

The results of the experiments also revealed that when viscosity of the size paste increased, the yarn’s abrasion resistance also increased. When the leasing yarn tension increased, the yarn abrasion resistance decreased. At high leasing tension the frictional contact between the sized yarn and the leasing rod increased, this will remove the size material from the yarn surface and leads to reduction in the abrasion resistance of the yarn. The creel zone yarn tension and yarn twist have a negligible effect on the abrasion resistance of the sized yarn.

Conclusion

The use of the proper sizing ingredients and improved process control in the sizing process result in the greatest performance of sized yarns. The problem associated with the sized yarn quality is caused by a variety of sizing machine settings, size paste recipe preparation and yarn properties.

The result of this study showed that gain strength of sized yarn is highly influenced by the viscosity of sized paste. It has 34.57% contribution and has positive effect on gain strength of sized yarn. For stretch percentage and the loss elongation of sized yarn the wet tension is the most significant factor to be controlled during processing and they have about 50.30% and 52.13% contribution for loss of elongation and stretch respectively. In general the tensile properties of sized yarns were affected by the wet zone warp yarn tension severely followed by viscosity of the size paste. On the other hand, speed of sizing machine affected the size pick up and abrasion resistance of the sized warp yarn dominantly than the other factors involved in this research with percentage contribution of 44.45% and 56.29% respectively.

Furthermore, the impact of factors involved in sizing process of cotton warp yarns on the major quality parameters of sized yarn is identified and ranked according to their effect on the quality parameters of sized yarn. Future work will entails optimization of the three or four most significant factors obtained in this research using response surface methodology to attain the best sized yarn properties in all aspects.

Authors’ contribution

Author1: Andinet Habtamu

Data collection, designing the experiment, conducting the experiment, and analysis of data.

Author 2: Million Ayele

Conception or design, writing the manuscript, and final approval of the version to be published.

Ethical approval

The content of this research doesn’t involve human or animal use.

Highlights

• The study reveals that the quality of sized yarn is influenced by various factors, including sizing machine settings, recipe preparation, and yarn properties.

• Viscosity of sized paste significantly influences gain strength, while wet tension is the most significant factor affecting stretch percentage and loss elongation.

• Speed of sizing machine is the dominant factor affecting size pick percentage and yarn abrasion resistance.

• The viscosity of size paste, yarn twists level, and wet tensions are the most influential factors to control in the sizing process.

Acknowledgments

The authors would like to acknowledge the Ethiopian Institute of Textile and Fashion Technology, Bahir Dar University, Bahir Dar, Ethiopia for the support of this project.

Disclosure statement

No potential conflict of interest was reported by the author(s).