Fabrication punching

Within the plane of a nonwoven material, the fibers may be either completely isotropic or there may be a preferred fiber orientation or alignment usually with respect to a machine or processing direction. In the case of thicker dry-laid nonwovens, fiber orientation may be randomized in the third dimension, ie, that dimension which is perpendicular to the plane of the fabric, by a process known as needle-punching (7). This process serves to bind the fibers in the nonwoven by mechanical interlocking. 

Typical textile fibers used, for example, in a needle-punched filter fabric, are a blend of 3.3- and 6.6-dtex (3- and 6-denier) polyester staple. These fibers are - 5 cm long, have diameters ranging from 18 to 25 pm, mass-per-unit-length or linear density values ranging from - 350 to 650 mg per 1000 m, and length-to-width ratios in the order of 1000 to 1. 

The basic elements of a needle-punch machine, or needle loom, are illustrated ia Figure 7 and consist of a web-feeding mechanism, a needle beam with a needle board and needles (ranging ia number from 500 to 7500 per meter of machine width), a stripper plate, a bed plate, and a fabric take-up mechanism. 

Principle appHcations of needle-punched nonwovens for the 1990s include automotive, apparel components, blankets, carpeting, carpet pa dding, coating substrates, filtration, furniture, geotextiles, insulation, roofing substrates, and wall coverings. In 1990, the production of needle-punched fabric was estimated to approach 91,000 t and 606 million square meters (15). 

Fig. 2. Typical stress—strain curves of nonwoven fabrics, where (—) is woven (-), thermally bonded nonwoven and (-), needle-punched...

Geotextiles. Nonwoven fabrics have played an important part in the development of geotextile appHcations. Both needle-punch fabrics... 

Spunbonded fabrics have a relatively small percentage of the coated fabric market which is dominated by other nonwovens. Needle-punched nonwovens offer more of the bulk and resiHency required for functionaHty in automotive and furniture seating. 

Nonwoven fabrics are generally described by the method of production, eg, needle-punched or spun-bonded (120). ASTM D1117 discusses various physical properties to be deterrnined for nonwoven fabrics and the standard procedures used. 

There are many completely automated computer-controUed exhaust dyehouses. Some firms have a no-add procedure in the dyehouse by which the dyer loads the fabric or yam, weighs the dye, punches a button, and lets the computer take over the entire process. This procedure ensures a constant dyeing cycle and the only variables are the dye index of the fiber or the quaHty of the dyestuff. 

Pollutant Loading Typical inlet concentrations to cartridge collectors are 1 to 23 grams per cubic meter (g/m ) (0.5 to 10 grains per cubic foot (gr/ft )). Cartridge filters, which utilize synthetic, nonwoven media such as needle punched felts fabricated of polyester or Nomex, are able to handle inlet concentrations up to 57 g/m (25 gr/ft ). 

The fabrication of all trays may be punched or drilled (more expensive) with 1410 holes, and those in the lower section have blank strips placed over the inlet and outlet edge rows until approximately 1223 holes are left open in the top section above the feed tray. 

Tungsten sheets or rods can readily be fabricated by bending, spinning, flow turning, punching, stamping and riveting, provided that work is carried out... 

Some ductile plastics, such as PC and ABS, can be fabricated like metals with punching and cold-forming techniques. These processing techniques are analogous to the hardness tests in that a rigid indentor is pressed into a sheet of a less-rigid plastic. 

The specimen has no specified size. Specimens for this test may consist of any standard fabricated test specimen or cut/punch pieces of sheet or machined sample. Specimens are mounted outdoors on racks slanted at 45° and facing south. It is recommended that concurrent exposure be carried out in many varied climates to obtain the broadest, most representative total body of data. Sample specimens are kept indoors as controls and for comparison. Reports of weathering describe all changes noted, areas of exposure, and period of time. 

Tools include dies, molds, mandrel, jigs, fixtures, punch dies, etc. for shaping and fabricating parts (Tables 8-13 and 8-14). 

In nonwoven geotextiles, the fibers are much thinner but far more numerous. The various types are needle-punched, resin-bond, and melt-bond. All contain a labyrinth of randomly oriented fibers that cross one another so that there is no direct line of flow. The fabric must have enough open space to allow liquid to pass through, while simultaneously retaining any upstream movement of particles. The needle-punched nonwoven type is very commonly used as a filter material. 

A sharp tool used in punching out special shapes of rubber or rubbered fabric or used in... 

As shown in Figures 1.36(a) and 1.36(b), the glycine nitrate process-derived powder is highly porous. The pore size ranges from tens of nanometers to several micrometers. The powder is thus named as foam powder, which shows extremely low fill densities of less than 1/100 of the theoretical density value. The low fill density makes it possible to prepare thin films of doped ceria by dry pressing, in which the films are processed by means of punches in a hardened metal die. Figures 1.36(c) and 1.36(d) show a cross-sectional view of an 8 /tm-thick GDC film fabricated by dry pressing. 

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