**3. Experimental**

**Figure 8.** Composition of Baby Diaper [41]

The advantages of super absorbent fibers [41] are as follows:

the liquid in [41].

20 Non-woven Fabrics

user.

Superabsorbent material was first produced in the early 1970s in Japan and USA. It was introduced into baby diapers in the early 1980s and later that decade into adult incontinence pads. By the early 1990s, superabsorbent material had become widely used in disposable baby diapers/nappies and incontinence products [41]. The use of superabsorbent materials in fiber form has now become a commercial reality. The majority of superabsorbent material available for today's absorbent hygiene products market is sold in granular form; some superabsorbent material is also available as a fiber. The granular material is a polymer made up of millions of identical units of sodium acrylate formed into a chain fence like structure. These are then linked to make the material into a three dimensional network. In their dry state, the long polymer chains are coiled. When they absorb liquid, they uncoil and the network expands. The liquid is then stored in the spaces in the molecular network and the material forms a gel which locks

**1. They help keep the skin dry.** This is done by drawing the liquid away from the skin and absorbing and retaining it in the core of the product. This creates greater comfort for the

**2. They help protect against skin irritation in diaper users by reducing skin wetness.** If skin becomes too wet, it is more vulnerable to irritation because the natural balance of the

**3. They help prevent the spread of infections.** The containment of fluid in the superab‐ sorbent core reduces leakage. It also reduces the risk of urine mixing with other material

skin, which helps protect against harmful bacteria, can be compromised.

This chapter focuses on the effects of fiber type, applied force, mass per unit area, contact surface, and fabric direction on the friction behavior of % PP and PES spunbond nonwoven fabrics. These samples have been used in medical packages, aprons, cleaning cloths, make up cleaning pads, protective cloths, wet towels, and home textiles. Therefore, it is important to evaluate friction behavior of nonwoven fabrics. Spunbonded nonwoven fabric samples (100 % polypropylene (PP) and polyester (PES)) were tested. While evaluating samples, Textile-Test Methods For Nonwoven-Part 3: Determination of Tensile Strength and Elongation and Textile-Test Methods For Nonwoven-Part 2: Determination of Fabric Thickness, ISO 9073-2, 1995 standards are used under standard test conditions. Some of the physical characteristics of nonwoven fabrics are given in Table 6. Before friction tests, a digital stereo microscope connected to computer (Figure 9) is used to examine surface view of samples [42].


**Table 6.** Physical properties of nonwoven fabrics

Frictional properties of nonwoven fabrics have been tested by using horizontal working principle device. This device is named as "horizontal platform experiment device." The mechanism is developed which is shown in Figure 10 by designing and extra changes upon conventional universal tensile tester in order to perform friction experiments. The designed and manufactured device consists of anti friction rollers (3,4), non-stretch yarn (5), a sled (6), and a sled bed (7). A non-stretch yarn (5) is passed through rollers (3,4) to upper carrier claw **Weight (g/m<sup>2</sup>**

nonwoven fabrics are given in Table 5. Before friction tests, a digital stereo microscope

**<sup>12</sup>** Polypropylene (PP) 0.10 23.0 11.0 40.0 40.0

**<sup>17</sup>** Polypropylene (PP) 0.11 45.0 40.0 65.0 65.0

Polyester (PES) 0.07 20.0 10.0 15.0 19.0

Polyester (PES) 0.09 30.0 14.0 18.0 21.0

Polyester (PES) 0.75 114.0 150.5 45.3 21.4

**Tensile Strength (N/5 cm)** 

**MD CD MD CD** 

**Elongation (%)** 

connected to computer (Figure 9) is used to examine surface view of samples [42].

**(mm)** 

**Table 5.** Physical properties of nonwoven fabrics

**) Raw Material Thickness** 

**Figure 9.** Microscope Views of Nonwoven Fabrics: (a) 12 g/m2

(c, 40×) (d, 40×)

Polypropylene, (b) 12 g/m2

Polyester, (c) 100 g/m2 Polypropylene, (d) 100 g/m2 Polyester **Figure 9.** Microscope Views of Nonwoven Fabrics: (a) 12 g/m2 Polypropylene, (b) 12 g/m2 Polyester, (c) 100 g/m2 Poly‐ propylene, (d) 100 g/m2 Polyester

(1) of tensile tester. Fastening the sample to the circular sled (6) made of circular 50mm diameter Delrin material is ensured by using a clip in proper dimensions. Nonwoven fabric (10) sample which is covered on sled (6) is lay out in the same direction (MD and CD) with horizontal platform [42]. 24

Sled bed (7) is designed with the aim of stretching the fabric (10) on experiment table (8) so as to hold it stable and to prevent slipping, curling, twisting, or folding during the experiment. While the upper carrier claw (1) of developed device is moving at a specific speed, it also pulls Delrin sled (6), and as a result, a friction occurs between two surfaces. At the same time, the load changes stemming from fabric surface structure created during the movement are perceived by load cell (2) and created in graphical and numerical values by the computer (42).

All nonwoven samples were conditioned according to ISO139 before tests, and tests were performed in the standard atmosphere of 20±2°C temperature, and 65±5% relative humidity.

(1. Upper Carrier Claw, 2. Load Cell, 3,4. Anti fiction Roller, 5. Non-stretch Yarn, 6. Sled, 7. Sled Bed, 8. Experiment Table, 9. Sponge, 10. Fabric, 11. Computer)

**Figure 10.** Horizontal Platform Experiment Device [42,43]

Design Expert 6.01 statistical package program is used to analyze data obtained by experi‐ mental works according to variance analysis at *α = 0.05* significance. Obtained analysis of variance (ANOVA) table is summarized in the following section, where *p value* less than 0.05 means that mentioned assessed factor has significant impact. Regression models were formed to define the relationship between independent variables (mass per unit area, fiber type, applied force, contact surface, and fabric direction), and response variables (static and kinetic friction coefficient).

While conducting statistical analysis, fiber type, contact surface, and fabric direction were accepted as categorical, whereas fabric mass per unit area and applied force were accepted as numerical factors. The frictional behavior of samples was used to analyze the general factorial design. The analysis of variance, lack of fit tests, and residual analysis were performed to select the proper model for the friction behavior.

#### **3.1. Results and discussion**

(1) of tensile tester. Fastening the sample to the circular sled (6) made of circular 50mm diameter Delrin material is ensured by using a clip in proper dimensions. Nonwoven fabric (10) sample which is covered on sled (6) is lay out in the same direction (MD and CD) with horizontal

**Figure 9.** Microscope Views of Nonwoven Fabrics: (a) 12 g/m2

**Figure 9.** Microscope Views of Nonwoven Fabrics: (a) 12 g/m2

Polyester

Polypropylene, (d) 100 g/m2

(c, 40×) (d, 40×)

Polyester

Polypropylene, (b) 12 g/m2

Polypropylene, (b) 12 g/m2 Polyester, (c) 100 g/m2 Poly‐

(a, 40×) (b, 40×)

nonwoven fabrics are given in Table 5. Before friction tests, a digital stereo microscope

**<sup>12</sup>** Polypropylene (PP) 0.10 23.0 11.0 40.0 40.0

**<sup>17</sup>** Polypropylene (PP) 0.11 45.0 40.0 65.0 65.0

**<sup>100</sup>**Polypropylene (PP) 0.49 200.0 163.0 70.0 71.0

Polyester (PES) 0.07 20.0 10.0 15.0 19.0

Polyester (PES) 0.09 30.0 14.0 18.0 21.0

Polyester (PES) 0.75 114.0 150.5 45.3 21.4

**Tensile Strength (N/5 cm)** 

**MD CD MD CD** 

**Elongation (%)** 

connected to computer (Figure 9) is used to examine surface view of samples [42].

**(mm)** 

**Table 5.** Physical properties of nonwoven fabrics

**) Raw Material Thickness** 

**Weight (g/m<sup>2</sup>**

22 Non-woven Fabrics

Sled bed (7) is designed with the aim of stretching the fabric (10) on experiment table (8) so as to hold it stable and to prevent slipping, curling, twisting, or folding during the experiment. While the upper carrier claw (1) of developed device is moving at a specific speed, it also pulls Delrin sled (6), and as a result, a friction occurs between two surfaces. At the same time, the load changes stemming from fabric surface structure created during the movement are perceived by load cell (2) and created in graphical and numerical values by the computer (42).

24

All nonwoven samples were conditioned according to ISO139 before tests, and tests were performed in the standard atmosphere of 20±2°C temperature, and 65±5% relative humidity.

platform [42].

Polyester, (c) 100 g/m2

propylene, (d) 100 g/m2

Friction tests were conducted under five loads (7.4, 10.2, 14.5, 17.3, and 20.2 N) and from three points of the fabric for machine direction (MD) and cross direction (CD) of samples and under three friction environment (fabric-abrasive wool fabric, wood, and metal). At the end of friction tests, the highest value for the movement at its start was accepted as static friction resistance, whereas the average of values read thereafter were accepted as kinetic friction resistance. Attention was paid to ensure that the sample attached to Delrin part which was placed on horizontal platform was slightly strained and rubbed to different parts of the fabric. Figures obtained using the test results of friction behavior of nonwoven fabric obtained in the tests are given Figures 11-14 [42].

In Figures 11 and 12, the change against applied force (load) of static friction forces obtained as a result of friction tests conducted at machine direction (MD) and cross direction (CD) under three friction platforms of 100% PP- and PES-based nonwoven surfaces of three weights is shown [42].

When these figures are examined, it can be observed that when the force in normal direction (vertical direction) applied on the sample increased, static friction coefficient values tended to decrease. The result for this effect is interpreted to be the more uniform fabric surface created by fabric friction interaction as load increased, as a result of which friction coefficient tended to decrease [42].

When the impact of fiber type on friction coefficient is viewed, it can be seen that friction coefficient values of polypropylene (PP)-based nonwoven fabrics had much lower values than those of polyester (PES)-based samples. This is believed to have been caused by the fact that polypropylene-based samples had a tougher surface. As the surface is smoother, less force is required for sliding action so as to move when compared to polyester-based nonwoven fabrics, in which case friction coefficient values were measured much lower [42].

In addition, we can see that fabric mass per unit area has a significant impact on friction values. As the fiber orientation of nonwoven fabrics with low weight is not smooth, they showed fluctuations in behaviors, and it has been seen that they had higher friction coefficient. However, it has been found out that as weight increases, friction coefficient values started to decrease as fiber orientation on nonwoven fabric surface was more stabile. When one looks at microscope views in Figure 9a and 9b belonging to fabric samples, it can be seen that fiber orientation distributed irregularly, and that as fabric weight increased (Figure 9c and 9d), surface smoothness deteriorated. This structure of the used samples helps us in understanding the obtained findings [42].

When these figures are examined, it can be observed that kinetic friction coefficient values in CD direction of samples at different friction surfaces (abrasive wool fabric, wood and metal) are slightly higher when compared to MD direction. The reason for this result can be the fact that fiber orientation in CD direction is more preventive for friction movement in the formation of samples [42].

When each load group of same type of sample is examined in itself, it can be observed that as the force in applied normal direction (vertical direction) increases, kinetic friction coefficient values tend to decrease. The result for this effect is interpreted to be the more uniform fabric surface created by fabric friction interaction as load increased, as a result of which friction coefficient tended to decrease [42].

**Figure 11.** MD Static Friction Coefficient

tests, the highest value for the movement at its start was accepted as static friction resistance, whereas the average of values read thereafter were accepted as kinetic friction resistance. Attention was paid to ensure that the sample attached to Delrin part which was placed on horizontal platform was slightly strained and rubbed to different parts of the fabric. Figures obtained using the test results of friction behavior of nonwoven fabric obtained in the tests are

In Figures 11 and 12, the change against applied force (load) of static friction forces obtained as a result of friction tests conducted at machine direction (MD) and cross direction (CD) under three friction platforms of 100% PP- and PES-based nonwoven surfaces of three weights is

When these figures are examined, it can be observed that when the force in normal direction (vertical direction) applied on the sample increased, static friction coefficient values tended to decrease. The result for this effect is interpreted to be the more uniform fabric surface created by fabric friction interaction as load increased, as a result of which friction coefficient tended

When the impact of fiber type on friction coefficient is viewed, it can be seen that friction coefficient values of polypropylene (PP)-based nonwoven fabrics had much lower values than those of polyester (PES)-based samples. This is believed to have been caused by the fact that polypropylene-based samples had a tougher surface. As the surface is smoother, less force is required for sliding action so as to move when compared to polyester-based nonwoven fabrics,

In addition, we can see that fabric mass per unit area has a significant impact on friction values. As the fiber orientation of nonwoven fabrics with low weight is not smooth, they showed fluctuations in behaviors, and it has been seen that they had higher friction coefficient. However, it has been found out that as weight increases, friction coefficient values started to decrease as fiber orientation on nonwoven fabric surface was more stabile. When one looks at microscope views in Figure 9a and 9b belonging to fabric samples, it can be seen that fiber orientation distributed irregularly, and that as fabric weight increased (Figure 9c and 9d), surface smoothness deteriorated. This structure of the used samples helps us in understanding

When these figures are examined, it can be observed that kinetic friction coefficient values in CD direction of samples at different friction surfaces (abrasive wool fabric, wood and metal) are slightly higher when compared to MD direction. The reason for this result can be the fact that fiber orientation in CD direction is more preventive for friction movement in the formation

When each load group of same type of sample is examined in itself, it can be observed that as the force in applied normal direction (vertical direction) increases, kinetic friction coefficient values tend to decrease. The result for this effect is interpreted to be the more uniform fabric surface created by fabric friction interaction as load increased, as a result of which friction

in which case friction coefficient values were measured much lower [42].

given Figures 11-14 [42].

shown [42].

24 Non-woven Fabrics

to decrease [42].

the obtained findings [42].

coefficient tended to decrease [42].

of samples [42].

**Figure 12.** CD Static Friction Coefficient In Figures 13 and 14, the change against applied force (load) of kinetic friction forces obtained as a result of friction tests conducted at machine direction (MD) and cross direction (CD) under three friction platforms of 100% PP- and PES-based nonwoven surfaces of three weights is shown [42].

When we look at the impact of different friction environments on friction behavior, the lowest friction coefficient values were witnessed in fabric-metal friction environment, and the highest friction coefficient values were obtained in abrasive wool fabric friction environment. As metal surface is more smooth and slippery compared to wooden and abrasive wool fabric, it is observed that metal showed smaller resistance to friction, hence lower values for friction of metal in this interaction. In addition, in fabric-abrasive fabric friction environment, as a result of the tests applied in both machine and cross directions, higher kinetic friction coefficient values were measured, especially in 17 g/m2 mass per unit area nonwoven fabric sample, compared to other samples. This is interpreted to have been caused by irregular distribution of fiber orientation in samples with low weight [42].

As a result of friction tests realized under fabric wooden friction environment, kinetic friction coefficient values were higher for polyester-based samples (especially 100 g/m2 ) as weight of surface structure in both machine and cross directions increased and gained a softer structure. As for polypropylene-based samples, on the other hand, as mass per unit area increased, surface structure became smoother and therefore friction coefficient tended to decrease [42].

In fabric-metal friction environment, as mass per unit area increased, friction coefficient values for both samples tended to increase as well, which is interpreted to have been caused by the softening of surface [42].

**Figure 13.** MD Kinetic Friction Coefficient

The statistical analyses show that the best fitting model is the quadratic model for spunbond nonwoven fabrics (Tables 7 and 8).

**Figure 14.** CD Kinetic Friction Coefficient

When we look at the impact of different friction environments on friction behavior, the lowest friction coefficient values were witnessed in fabric-metal friction environment, and the highest friction coefficient values were obtained in abrasive wool fabric friction environment. As metal surface is more smooth and slippery compared to wooden and abrasive wool fabric, it is observed that metal showed smaller resistance to friction, hence lower values for friction of metal in this interaction. In addition, in fabric-abrasive fabric friction environment, as a result of the tests applied in both machine and cross directions, higher kinetic friction coefficient

compared to other samples. This is interpreted to have been caused by irregular distribution

As a result of friction tests realized under fabric wooden friction environment, kinetic friction

surface structure in both machine and cross directions increased and gained a softer structure. As for polypropylene-based samples, on the other hand, as mass per unit area increased, surface structure became smoother and therefore friction coefficient tended to decrease [42].

In fabric-metal friction environment, as mass per unit area increased, friction coefficient values for both samples tended to increase as well, which is interpreted to have been caused by the

The statistical analyses show that the best fitting model is the quadratic model for spunbond

coefficient values were higher for polyester-based samples (especially 100 g/m2

mass per unit area nonwoven fabric sample,

) as weight of

values were measured, especially in 17 g/m2

softening of surface [42].

26 Non-woven Fabrics

**Figure 13.** MD Kinetic Friction Coefficient

nonwoven fabrics (Tables 7 and 8).

of fiber orientation in samples with low weight [42].


**Table 7.** Model summary statistics (static)

ANOVA results for friction coefficient of nonwoven fabric samples are given in Table 9. When ANOVA table is examined, it can be seen that weight, fiber type, applied force, and contact surface of nonwoven fabrics have significant impact on friction coefficient values, whereas fabric direction showed no significant impact. In addition, according to the table, the R2 value of the model turned out to be some 0.86. In this case, terms in the model can explain the model at 86% ratio. This case shows that the model created for friction coefficient can express with rather high accuracy the relation between independent variables and dependent variable and that experimental work results were acceptable as accurate [42].


**Table 8.** Model summary statistics (kinetic)


**Table 9.** ANOVA table

The regression equation of the quadratic model for spunbond nonwoven sample is as follows;

Static Friction Coefficient = 0.24 + 0.00364×A - 0.019×B-0.015×C + 0.045×D + 0.003×E - 0.001931×AC - 0.023×AD + 0.005×BD - 0.16×A2

Kinetic Friction Coefficient = 0.24 + 0.004678×A - 0.017×B - 0.013×C + 0.047×D - 0.004×E + 0.00012×AC - 0.022×AD + 0.0060×BD - 0.17×A2

According to model performance values, the correlation coefficient between predicted and observed air permeability values is 0.85, indicating a strong predictive capacity of the regres‐ sion model for spunbond nonwoven samples.

**Figure 15.** Normal Plot of Residual Coefficient of Friction Values: (a) Static and (b) Kinetic

Figure 15 gives normal distribution graph of residuals for quadratic model. As can be seen from the figure, no problems are observed in normal distribution in the chosen model. This analysis also supports the conformity of chosen model.
