Nonwoven fabrics uniformity

The nonwoven fabric uniformity is originally defined as the fabric mass per unit area (or fabric density) distribution in the fabric structure. The basic statistic terms of fabric mass uniformity in nonwoven industries are the standard deviation (measured parameters (eg, fabric weight, fabric thickness, fabric density, optical levels, rays absorption amounts, grey level intensity of images, etc.) as follows ... 

Other reinforcements that may be used in the substrate layers of decorative laminates and throughout the stmcture of industrial laminates are woven fabrics of glass or canvas and nonwoven fabrics of various polymeric monofilaments such as polyester, nylon, or carbon fibers. Woven and nonwoven fabrics tend to be much stronger than paper and have much more uniform strength throughout the x—y plane. They greatly enhance properties of laminates such as impact and tear strength. 

Adhesives and Sealants. Most industrial adhesives contain surface active components and additives, and air entrainment during their mechanical appHcation can significantly reduce joint strength. Defoamers are usually formulated into adhesives to protect users against such difficulties. Additional benefits, such as improved uniformity of products, increased throughput and reduced labor costs can also result from the use of defoamers during adhesive appHcation. The footwear and nonwoven fabric industries are extensive users of defoamers in this way. 

Not only surface fibres are coated with metal (fig 2a), but also the nonwoven fabrics internal fibres (fig. 2b) and areas between fibres (fig. 2c). Similar crystallization are observable for zinc layers deposited on polypropylene film (fig. 3). A layer obtained in that manner characterises with large sp>eafic surface area, which disperses electromagnetic field and increases shielding coefficient SE at the same time. Cross-section of such compwsite is presented in Fig. 4. It comes to one s attention that metaUic layers on fibre surface are solid and uniform. Best composites characterise with SE 60 dB, which not only stems from low surface resistivity, but also from expanded surface of metaUic layers (fig. 5). 

Boettcher and Schilde note that the use of recycled fiber in the manufacture of nonwoven fabrics is expected to continue increasing. However, a serious problem is the lack of uniform quality of the recycled fiber. They refer in particular to improperly opened fibers and to too much variability in fiber length. They suggest that the development of an effective device for separating long and short fibers would contribute towards the growth in this aspect of the business. 

The structure and properties of a nonwoven fabric are determined by, in addition to the properties of the constituent fibres and bonding materials, the stmctural architecture of fibres, bonding segment structure, and their distributions. The methods for the measurement of the key structural parameters of nonwoven fabrics discussed in this section include fabric thickness, mass per unit area, fabric density, fabric uniformity fabric porosity, pore size and pore size distribution, fibre orientation distribution, bonding segment structure, and their distributions. 

Nonwoven fabric mass per unit area, bulk density, and fabric uniformity... 

The fabric uniformity is anisotropic, ie, the uniformity is different in different directions in fabric structures, notably, in machine direction (MD) and cross direction (CD). The ratio of the index of dispersion was roughly used to represent the anisotropy of uniformity. The local anisotropy of nonwoven fabrics mass uniformity has also been defined by Scharcanski and Dodson in terms of local dominant orientations of fabric weight. 

With optical light measurement method, the nonwovens are evaluated for uniformity on optical electronic method, which screens the nonwoven to register 32 different shades of grey. The intensity of the points in the different shades of grey provides a measure of the uniformity. A statistical analysis of the optical transparency and the fabric uniformity is then produced. This method is suitable for nonwovens in the weight range of 10—50 gsm. When the optical light measurement... 

Nonwoven fabric filters could be designed as uniform and homogeneous stmctures as a filtrahon element they are also frequently engineered into composite stmcture, gradient stmcture, and layered stmctures with the help of combined nonwoven technologies. 

Roller materials are supplied to the inner side of the resin under the driving force provided by the rotation of the screw of the TSE. If nonwoven fabric of considerable length is used, a pellet of uniform composition will be manufactured by continuous mnning. 

Nonwoven fabrics are another form of fiber assemblage, but they are less regular and uniform in structure than woven fabrics. A qualitative evaluation of nonwoven samples has been shown using a special stain (Pylam Products Co., Tempe, AZ) to identify fibers including polyester, rayon, wood pulp, and polypropylene as well as various blends and bonding points and binder distribution [50]. A spray spun nonwoven is shown in side view (Fig. 5.10A) on an SEM stub, and a surface view (Fig. 5.10B) shows the fabric has a range... 

As the new century began, we saw new beginnings in spunbond processes and products. New techniques are being developed to improve uniformity and barrier properties of spunbond fabrics to allow spunbond to compete successfully with carded thermal bonded nonwovens. Fabrics from new polymers and polymer combinations are poised to enter the market. Tactile as well as tensile properties are being improved to the point where even apparel applications may be considered as a future market (Anon., 2011). Several of these trends are described in the following paragraphs. 

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