**3. Materials and methods**

#### **3.1. Materials**

In this research, all spunbonded and meltblown nonwoven fabrics were supplied by Mogul Nonwoven Company in Gaziantep/Turkey. Raw material of all layers was polyester with the advantages of availability, flexibility, and commercially success. Spunbonded layers, flat bonded thermally, having a basis weight of 40 gsm, were produced from homocomponent and bicomponent fibers in the diameter of 20–24 μm. Seven different meltblown layers had a basis weight of 50–200 gsm with homocomponent round fibers at the diameter of 5–8 μm. Meltblown nonwovens were bonded thermally at same conditions to form nonstiffer middle layer of multilayer structures. SMS compositions of two different spunbonded layers and seven different meltblown layers were prepared manually, resulting in 14 multilayer nonwoven structures. Layers were arranged loosely, adjacent to each other. Fabric design of multilayer structures has been illustrated in **Figure 3**.

Description of multilayer nonwoven samples is shown in **Table 1**. The thickness of the samples ranged from 1.28 to 1.79 mm. From **Table 1**, the samples were coded as HC and BC according to the change of fiber type in the spunbond layers; sample codes of 1, 2, 3, 4, 5, 6, and 7 defined the changes in basis weight of the meltblown layers. For instance, HC1 designates an SMS type three-layered nonwoven in which the outer spunbonded layers with homocomponent round fibers and a meltblown layer have a basis weight of 50 gsm; BC7 means spunbonded layers with bicomponent fibers and meltblown layer having a basis weight of 200 gsm.

**3.2. Methods**

**Sample ID**

HC Spunbonded layers

1 Meltblown layer

meltblown layer (in basis weight of 125 gsm).

**Type of layer Fiber type Fiber** 

**Table 1.** Sample description and specifications of nonwoven layers.

BC Bicomponent PET/

All measurements were carried out at standard temperature (20 ± 2°C) and relative humidity (65 ± 2%). The thickness of the 10 different samples from each material was measured using a

**Figure 3.** Schematic of multilayer structure and SEM micrographs of spunbonded layers (homocomponent fibers) and

**Fiber cross section Basis weight** 

Homocomponent PET Round 40 0.37 ± 0.07

Homocomponent PET Round 50 0.59 ± 0.09

Bico-round/ sheath-core type **(gsm)**

Acoustic Insulation Behavior of Composite Nonwoven http://dx.doi.org/10.5772/intechopen.80463 47

**Thickness (mm)**

0.35 ± 0.05

**content**

Co-PET

 75 0.60 ± 0.08 100 0.62 ± 0.06 125 0.67 ± 0.07 150 0.84 ± 0.05 175 0.93 ± 0.06 200 1.1 ± 0.04

Air permeability of multilayer nonwovens was obtained by using an SDL Atlas digital air permeability tester (SDL-Atlas Inc., USA). The test were conducted according to NWSP 070.1.R0

standard measuring device according to NWSP 120.6.R0 (15) [16].

In this research, bicomponent fibers, round core/sheath type, in the spunbonded layers have a polyester core with an outer sheath of copolyester. The composition of polymers in core/ sheath type is 90% polyester (PET) core with 230–250°C melting point and 10% copolyester (Co-PET) sheath with 110–140°C melting point.

**Figure 3.** Schematic of multilayer structure and SEM micrographs of spunbonded layers (homocomponent fibers) and meltblown layer (in basis weight of 125 gsm).


**Table 1.** Sample description and specifications of nonwoven layers.

#### **3.2. Methods**

One of the applications in thermal bonding in spunbonded process is producing web consisting of bicomponent fibers. Bicomponent fibers contain two different polymers extruded together from the same spinneret to compose a single fiber cross section. The properties and applications of bicomponent fibers depend on both the properties and distribution of the polymers in the cross-sectional area. Accordingly, typical configurations are side by side, core/sheath, island in the sea, sliced, pie slice, etc. The most commonly used in nonwovens and well-known binding bicomponent fibers is sheath/core type. When a bicomponent nonwoven web is heated sufficiently to melt the sheath, polymer melts and flows to the nearest adjacent fiber and binds the structure. It is recommended that the melting temperature difference between the components should be at least 40°C for proper bonding. Lower bonding temperature is provided by bicomponent fibers than in a typical thermal bonding application. Additionally, with this method, some structural parameters of a nonwoven fabric, such as fabric density, fiber diameter, tortuosity, porosity, etc., will

In this research, all spunbonded and meltblown nonwoven fabrics were supplied by Mogul Nonwoven Company in Gaziantep/Turkey. Raw material of all layers was polyester with the advantages of availability, flexibility, and commercially success. Spunbonded layers, flat bonded thermally, having a basis weight of 40 gsm, were produced from homocomponent and bicomponent fibers in the diameter of 20–24 μm. Seven different meltblown layers had a basis weight of 50–200 gsm with homocomponent round fibers at the diameter of 5–8 μm. Meltblown nonwovens were bonded thermally at same conditions to form nonstiffer middle layer of multilayer structures. SMS compositions of two different spunbonded layers and seven different meltblown layers were prepared manually, resulting in 14 multilayer nonwoven structures. Layers were arranged loosely, adjacent to each other. Fabric design of multi-

Description of multilayer nonwoven samples is shown in **Table 1**. The thickness of the samples ranged from 1.28 to 1.79 mm. From **Table 1**, the samples were coded as HC and BC according to the change of fiber type in the spunbond layers; sample codes of 1, 2, 3, 4, 5, 6, and 7 defined the changes in basis weight of the meltblown layers. For instance, HC1 designates an SMS type three-layered nonwoven in which the outer spunbonded layers with homocomponent round fibers and a meltblown layer have a basis weight of 50 gsm; BC7 means spunbonded layers with bicomponent fibers and meltblown layer having a basis weight of 200 gsm.

In this research, bicomponent fibers, round core/sheath type, in the spunbonded layers have a polyester core with an outer sheath of copolyester. The composition of polymers in core/ sheath type is 90% polyester (PET) core with 230–250°C melting point and 10% copolyester

be affected [15, 20].

46 Engineered Fabrics

**3.1. Materials**

**3. Materials and methods**

layer structures has been illustrated in **Figure 3**.

(Co-PET) sheath with 110–140°C melting point.

All measurements were carried out at standard temperature (20 ± 2°C) and relative humidity (65 ± 2%). The thickness of the 10 different samples from each material was measured using a standard measuring device according to NWSP 120.6.R0 (15) [16].

Air permeability of multilayer nonwovens was obtained by using an SDL Atlas digital air permeability tester (SDL-Atlas Inc., USA). The test were conducted according to NWSP 070.1.R0 (15) [17]. The measurements were done on five different samples from each material by applying 200 Pa pressure through a 20 cm<sup>2</sup> test area. The reported results are the averages of the five measurements.

**4. Experimental results and discussion**

are more resistant to air flow than the HC samples.

resulted with lower air permeabilities.

**Figure 5.** Air permeability of nonwoven samples.

Air permeabilities of nonwoven samples are presented in **Figure 5**, respectively, for increasing basis weights of multilayer nonwovens. As seen in **Figure 5**, the air permeabilities of the nonwoven samples with bicomponent fibers are lower than the air permeabilities of the nonwoven samples with homocomponent fibers. For each range of basis weight, BC samples

Acoustic Insulation Behavior of Composite Nonwoven http://dx.doi.org/10.5772/intechopen.80463 49

Air permeability is expressed as the ratio of air flow between the two surfaces of the fabric. The speed of the air flow passing vertically from a given area is measured by the pressure difference within the measuring area of the fabric. The degree of air permeability is one of the major affecting parameters of thermal and acoustic insulation capabilities of nonwoven

Co-PET polymer with low melting temperature in nonwoven samples containing bicomponent fibers melts during the thermal bonding and provides the binding by spreading to the fibers around the web. This attribute limits the cross sectional and connection between fibers, and when considering that it affects the fiber roughness, the decrease in pore diameters is determined by the pore size measurements. When the relationship between air permeability and pore structure is evaluated, it is thought that this will increase air flow resistance and create a decrease in air permeability values. This indicates that bicomponent structures restricted the size of air passages, so that air permeability decreased. At higher basis weights of the fabrics, the increase in the number of fibers creates more spaces and a longer tortuous path through which the air must flow. Thus fabric structure becomes more resistant to air flow

fabrics. Higher air permeability results in higher sound absorption [21–23].

**4.1. Air permeability**

Sound absorption coefficients of multilayer nonwovens were measured according to ISO 10534-2 [18]. Nonwoven samples were cut into 100 and 29 mm diameters for the measurement of large and small tubes. Sound absorption coefficients of three samples (two replications from each material) were obtained by using a Brüel and Kjær impedance tube kit (**Figure 4**).

The capillary flow porometer (Porous Materials Inc., USA) has been successfully used to evaluate pore structures of multilayer nonwovens. Determination of porosity of samples according to ISO 15901-1 standard, 5 samples were prepared at 0.03 cm and determined by taking the average of the measurement values [19].

In statistical analysis, Design Expert Analysis of Variance (ANOVA) software (Stat-Ease, Inc., USA) was achieved. The effect of independent parameters, basis weight (A) and fiber type (B) on the dependent parameters of air permeability, mean pore diameter, and sound absorption has been examined with the analysis of variance at significance level of p value less than 0.05.

**Figure 4.** Impedance tubes for the two microphone transfer function methods: (a) large tube for 0.5–6.4 kHz and (b) small tube for 0.5–1.6 kHz.
