Fabric finishing techniques

Fabric finishing processes are designed essentially to ensure that the fabric will (a) remain dimensionally stable during use, (b) provide effective cake release during the cleaning cycle, (c) meet the fabric s designed air permeability (a control parameter widely used in the industry) and (d) be protected, as far as possible, from any chemical conditions that may be encountered in the filter. 

It is well known that most synthetic fibres and continuous filament yams will to a greater or lesser extent shrink when exposed (in unrestrained state) to high temperatures. In addition, due to tensions imposed on fibres and yams during processing, further shrinkage is to be expected due to relaxation 

The relatively harsh surface created by the singeing process can be made smoother through the heat and pressure of a calendering process. The heated bowl in this operation is normally of chrome-plated steel composition, whereas the second bowl, which applies the pressure, usually comprises a somewhat softer material so as not to crush the fabric when the pressure 

The calendering process also increases the density of the fabric (especially needle felts) the pore size is reduced and dust penetration into the body of the needle felt thus restricted. In practice, the polymer type largely dictates the surface temperature of the heated bowl whilst the pressure, which may be up to 300 da N m and speed are adjusted to achieve the desired density and air permeability. 

A surface treatment that is not engaged for improved cake release purposes is the raising or napping process. This is usually applied to satin weave fabrics made with staple-spun fibres in the weft, and is designed to enhance particle collection efficiency by teasing the fibres of the staple-spun yam into a pile or nap. It will thus be appreciated that the treatment is normally applied to the reverse side of the fabric i.e. the side that does not collect the dust cake. 

---

Another fire-related problem that has seen some research effort is that of smolder resistance of upholstery and bedding fabrics. Finishing techniques have been developed to make cotton smolder-resistant (152—156), but the use of synthetic barrier fabrics appears to provide a degree of protection. Work also has provided a means of producing cotton fabrics that have both smooth-dry and flame-retardant performance (150,151). In this case, the appHcation of FR treatment should be performed first, and DP treatment should be modified to accommodate the presence of the FR polymer on the fabric. 

To build an efficient and compact microreactor, the fabrication technique must allow for three-dimensional structures and the use of the appropriate materials, and the technique should be low cost. Since reactants and products must flow in and out of the device, traditional standard thin film techniques are not suitable for the reactor framework. However, thin film techniques are very useful for integration, surface preparation, sensor integration, and finishing or packaging. Fortunately, traditional thin film techniques can be modified for microreactor fabrication other techniques, which will be discussed below, are also available. 

Silicones and flnorocarbon polymers cannot easily be stripped off, especially when they are crosslinked. As it is the natnre of repellent finishes to reduce adhesion, there are problems with backcoating and laminating of fabrics finished by padding flnorochemicals. One solntion is the one side application of the repellents by nip-padding, spray, foam or sqneegee techniques. 

The cotton fabrics were treated using conventional padding and foam-finishing techniques by United Merchants and Manufacturers. The two finishing agents used have the tradenames of Valrez 2i)8 and Valrez ULF. Valrez 2kB is dimethyloldihydroxyethyleneurea (DMDHEU) with the following structure ... 

Also, polymer parts, whether film and sheeting or rigid products, can be postfinished in a number of ways. Some companies within the polymers industry specialize in various finishing techniques. On the other hand, finishing, decorating, and assembly of the polymer end product can be done in-house by the processor or fabricator. 

Special characterization methods are required to access the effective transfer of the SME to a specific application. Evaluation techniques were developed for woven cotton fabrics finished with SMPs [79]. For characterizing shape-memory fabrics a shape-memory coefficient (5%) was introduced. In the experiment a test specimen was folded and compressed under controlled conditions of time and applied force to create a folded wrinkle. The samples were then immersed in water with a defined temperature to release the shape recovery process and later dried. The determination of this coefficient was based on the obtained average crease recovery angles of a series of samples ... 

Microcapsules can be applied on any fabric (woven, knitted, nonwoven or garments). The substrate may be wool, silk, cotton, flax, or synthetic fibers such as polyamide or polyester, or mixtures. Most of the microcapsules can be appHed using conventional finishing techniques without altering the feel and color of colored fabrics or printed patterns. Microcapsules can also be applied during the rinse cycle of a washing machine. 

---