Nonwoven fabrics mechanical properties

Nonwoven fabric properties and performance include nonwoven fabric mechanical properties (tensile, compression, bending, and stiffness) gaseous and liquid permeability, water vapour transmission rate (WVTR), liquid barrier properties, sound absorption properties, and dielectric properties. 

Sony s Introduction of the rechargeable lithium-ion battery in the early 1990s precipitated a need for new separators that provided not only good mechanical and electrical properties but also added safety through a thermal shutdown mechanism. Although a variety of separators (e.g., cellulose, nonwoven fabric, etc.) have been used in different type of batteries, various studies on separators for lithium-ion batteries have been pursued in past few years as separators for lithium-ion batteries require different characteristics than separators used in conventional batteries. 

Nonwovens The textile and paper industries are based on the two oldest (wet and dry) processes. Manufacturers of nonwovens for plastics draw on both. With the wet, there are basically two types namely the Fourdrinier and cylinder machine types that have been modified. In addition, two basic types exist for the process formation of the web and application of the bonding agent or system where mechanical carding of fibers is used. The particular equipment and method of operation to be used, with their many modifications, is influenced by desired requirements such as mechanical properties, softness, surface condition, tenacity, etc. There are certain t) es of so-called nonwoven fabric that are directly formed from short or chopped fiber as well as continuous filaments. They are produced by loosely compressing together fibers, yarns, rovings, etc. with or without a scrim cloth carrier assembled by mechanical, chemical, thermal, or solvent methods. Products of this type include melted and spun-bonded fabrics. 

Hwang Y J, Mccord M G, An J S, Kang B C and Park S W (2005), Effects of helium atmospheric pressure plasma treatment on low-stress mechanical properties of polypropylene nonwoven fabrics , Textile Research Journal, 75,771-778. 

Although the mechanical properties of constituent yams (fibres) are important for balhstic protection, the construction of fabrics can also have a significant effect on balhstic performance. Both nonwoven and woven fabric stmctures of various types with or without resin matrices have been used for ballistic applications. Typical nonwoven fabrics are felts , which are constmcted by randomly orienting and mechanically interlocking the fibres in a form of a web. In contrast, woven fabrics are constmcted through interlacing warp and weft yams. 

The basic concept employed in making a nonwoven fabric is to transform fiber-based materials into two-dimensional sheet structures with fabric-like properties. These are flexibility, porosity, and mechanical integrity. Their manufacturing processes can be split into four groups dry-laid webs, extrusion-formed webs, wet-laid webs, and web-bonding. 

After a fiber or yam is produced, it is then fabricated into a textile stmcture in order to obtain the desired form, shape, and mechanical properties for a medical device. There are four alternative types of textile stmctures that are typically used for medical devices. They include wovens, knits, braids, and nonwovens. Each stmcture has its own advantages and disadvantages. For example, woven fabrics are usually stronger and more dimensionally stable and can be fabricated with lower porosities, but are stiffer, less flexible, and more difficult to handle. Knits, on the other hand, have higher permeability and flexibility compared to woven fabrics, but may dilate after implantation. Braids have high longitudinal tensile properties, but can be unstable when subjected to torsional loads. Thus, the type of textile stmcture should be carefully selected when designing the biotextile device, and the medical application and the site of implantation should be taken into account. 

Yarns and fabrics are assemblages of fibers which have commercial application in the textile industry. The fabrics include those formed by weaving and also nonwovens. The geometry of the fabric, as well as the chemical composition of the polymer, influences mechanical properties and applications. The SEM is useful for evaluating (1) construction, (2) coverage, (3) uniformity, (4) surface structure and (5) effects of wear. 

The physical, chemical, and mechanical properties of nonwoven fabrics used in various industrial applications depend on the nonwoven fabric stmcture and the properties of its constituent materials. The changes of nonwoven fabric properties will entirely depend on the alteration of the nonwoven structural parameters if the component materials are kept unchanged. The testing methods (standard or nonstandard) to characterise the nonwoven structural parameters, properties, and performance of a few typical nonwoven products are discussed in this chapter part of such discussions and the relationship between nonwoven structure, properties, and performance could also be found elsewhere. ... 

The anisotropy of nonwoven structures can be characterised by using the anisotropy of FOD functions. It has been shown by many researchers that the anisotropy of nonwoven structures influences the anisotropy of mechanical and physical behaviour of the nonwoven fabrics, and FOD plays an important role among them. The anisotropies of these mechanical and physical properties include tensile properties, bending properties, anisotropy of thermal insulation properties, acoustic absorptions, dielectric properties, and directional permeabilities. 

The mechanical properties of nonwoven fabrics are determined by the properties of fabric constituents and the structural arrangement of these components. Among the important aspects of fibre morphology are fibre orientation, fibre curl and thickness. Their changes can affect the mechanical behaviour and failure mechanisms. These parameters can also be varied and controlled more easily during manufacture to improve fabric design and performance (Adanur Liao, 1999). 

Adanur, S., Liao, T. (1998). Computer simulation of mechanical properties of nonwoven geotextiles in soil-fabric interaction. Textile Research Journal, 68(3), 155—162. 

Currently, the top sheet of a disposable diaper is usually made from a hydrophilic nonwoven fabric. These nonwoven fabrics are broadly defined as sheet or web stractures bonded together by entangled fibres or filaments, and by perforating films mechanically, thermally, or chemically to form flat, porous sheets that are made directly from separate fibre or from molten plastic or plastic film. Therefore, the mechanical and smface properties of the hygienic nonwoven fabrics used as the top sheet of disposable diapers are important for the health and comfort of the skin (Hong, Kim, Kang, 2005). 

Li-ion cells use thin (10 to 30 /u,m), microporous films to electrically isolate the positive and negative electrodes. To date, all commercially available liquid electrolyte cells use micro-porous polyolefin materials as they provide excellent mechanical properties, chemical stability and acceptable cost. Nonwoven materials have also been developed but have not been widely accepted, in part due to the difficulty in fabricating thin materials with uniform, high strength. ... 

---