**2. Material and method**

246 Thermoplastic Elastomers

The main characteristics and properties of melt-blown nonwovens can be summarised as

Generally fibres with circular in cross-section but it can also be variable in some cases

 Variable fiber length over a broad range depending from a few millimeters to several hundred centimeters (Dahiya et al., 2004; Duran&Perincek, 2010; Dutton, 2008)

Meltblowing is a unique system since the process generates a fine fiber not available to the other nonwoven processes. Because the micro-denier fiber (less than 0.1 denier per filament) is not really available as a nonwoven fibrous raw material, the meltblown process, which can produce such a fiber, opens new vistas of products and applications. (Dahiya et al., 2004) Microfiber nonwovens produced via meltblowing technique are suitable to be used as thermal insulators, filtration media, oil absorbents, battery separators, medical area, wipes, apparel, laminates and many other applications. (Duran&Perincek, 2010, Dutton, 2008) Meltblown nonwovens find extensive use especially in absorbent cloths and wipes; oil absorption; and filtration for liquids, gas and air. Also, very important end uses of meltblowns include sanitary applications such as hygiene and incontinence products for babies, adults and feminine hygiene. The application areas of meltblown nonwovens can be summarised as follows: (Dahiya et al.,

Filtration media: surgical face mask filter media, liquid and gaseous filtration, cartridge

Oil adsorbents: sorbents to pick up oil from the surface of water, such as encountered in

Apparel: thermal insulation, disposable industrial apparel and substrate for synthetic

Electronic Specialities: liner fabrics in computer floppy disks, battery separators and as

Manufacture of tents and elastomeric nonwoven fabrics which have the same

appearance as continuous filament spunbonded products

 Medical fabrics: disposable gown and drape market and sterilization wrap segment Sanitary products: feminine sanitary napkin, disposable adult incontinence absorbent

an accidental oil spill and for mats in machine shops and in industrial plants

variable, ranging from circular to a flat configuration and other variations

follows:

2004)

products

leather

Hot melt adhesives

insulation in capacitors

 Low porosity Good absorbency

 Random fiber orientation. Lower to moderate web strength

Generally high opacity and a high cover factor

Good insulation and filtration characteristics

High surface area due to microfibers

Fibers with smooth surface texture

filters, clean room filters and others

 Fiber diameter in the range of 0.5 - 30 m, typically 2-7 m Basis weight in the range of 8-350 g/m2, typically 20-200 g/m2

> In this chapter, the results of a study about polypropylene microfibre meltblown nonwovens were covered. Aspects related to the production phase, properties of the materials produced and application areas were discussed. In the content of this study, effect of some production parameters namely die air pressure, collector drum speed, collector vacuum and extruder pressure on the physical properties of the web structure such as thickness, basis weight, air permeability, tensile properties, surface friction and fiber diameter were investigated.

> As raw material, PP with 1100 melt flow rate (MFR), 0.75 g/cm3 density and 335 F melting point was used. The main production settings namely; extruder temperatures, die temperature, air temperature (the air fed to the spinerette to spin the fibers), die hole diameter and die-to-collector distance were given in Table 1.


Table 1. Main production settings and their values used in experiments

The sample codes and production parameters of the PP melt blown nonwovens investigated in this study can be seen in Table 2.

The produced samples were characterized for thickness, basis weight, air permeability, fiber diameter and tensile properties.

Investigation of the Production Parameters and

**3. Results and discussions** 

nonwoven webs were investigated.

**3.1 Thickness** 

Physical Characteristics of Polypropylene Meltblown Nonwovens 249

In this study, influence of some crucial production parameters namely die air pressure, extruder pressure, collector drum speed, and collector vacuum on the thickness, basis weight, air permeability, fiber diameter and tensile properties of polypropylene meltblown

The results obtained from the thickness measurements were presented in Figure 1. The statistical analysis have shown that thickness of polypropylene meltblown nonwovens were effected mostly by the drum speed and the collector vacuum. An increase in the drum speed and an increase in the vacuum caused a decrease in the thickness. In other words, thicker surfaces were obtained with lower collector drum speeds and lover vacuum values. The

highest values were obtained with 10 ft/min drum speed and %15 vacuum.

Fig. 1. Thickness values of polypropylene meltblown nonwovens

lowest results were obtained with 20 ft/min as 0,0197 cm.

results were obtained with 60 ft/min as 0,0254 cm.

Statistical analyses also proved that the drum speed and collector vacuum on the thickness of meltblown nonwovens were statistically significant. The results of the tests between subgroups were shown in Table 3 and Table 4. As it can be seen in Table 3 and Figure 1, as a general trend the thickness increased with decreasing collector drum speed. Even though the thicknesses of the samples produced with 30 ft/min which were 0,0278 cm on average are slightly higher than the ones produced with 20 ft/min which were 0,0197 cm, the main trend did not change. The highest results were obtained with 10 ft/min as 0,0789 cm and the

As it can be seen in Table 4 and Figure 1, the effect of collector vacuum on the thickness was found to be statistically significant and the thickness increased with decreasing collector vacuum. The highest thickness results were obtained with 15% as 0,0602 cm and the lowest


Table 2. Sample codes and production parameters of PP nonwovens

Thickness was tested by using SDL Thickness Gauge according to TS 7128 EN ISO 5084 standard, with 20 cm2 measurement area under 200 g weight. Air permeability test was performed by using FX 3300 Air Permeability test device according to TS 391 EN ISO 9237 standard, with 20 cm2 measurement area and 100 Pa air pressure. Fiber diameter was measured by using Leica DM EP light microscope with 400 zoom. Tensile properties were tested according to TS EN ISO 13934-1 standard by using Zwick Z010 Universal tensile strength with 200 mm measurement distance and 100 mm/min measurement speed.

The results were evaluated statistically by using SPSS software. To evaluate the differences between the subgroups in the collector drum speed, the collector vacuum and the die air pressure Student-Newman-Kleus test were performed. For the investigation of the effect of the extruder pressure 2-Tailed Pearson Correlation tests were performed.
