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Polymer Technology
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
Calendering is the squeezing or extruding of a material between pairs of corotating parallel rollers to form films and sheets. It can be used to mix and form slightly melted matrix material into impregnated composite tapes. Sheets of material can be combined with sheets of impregnated paper and fiber woven and nonwoven mats forming laminar composite materials. Certain rubber material and textiles can also be processed using calendering. Calendering is can be employed in conjunction with other processing techniques such as extrusion in the formation of films from extruded material. It is also used to coat, seal, laminate, sandwich, finish, and emboss.
Finishing Processes and Recent Developments
Published in Asis Patnaik, Sweta Patnaik, Fibres to Smart Textiles, 2019
Andrew D. Hewitt, Andrew J. Hebden
Calendering is a finishing process where a fabric passes between two or more rollers (sometimes referred to as ‘bowls’) under set temperature and pressure conditions in order to alter its properties such as handle, surface texture and appearance. The number of rollers, roller design, roller speed, moisture, temperature and pressure can be varied to suit various fabrics and desired finishes. Calendering a fabric tends to reduce the thickness and air permeability, and increase the opacity, smoothness and lustre.
Finishing
Published in Michael Hann, Textile Design, 2020
Heat and/or pressure can be applied to cloths in order to improve their performance or appearance. Mechanical finishes include calendering, embossing and napping. Calendering involves passing cloth (full width), between heated pressure rollers, flattening the yarn, making the cloth softer and increasing its lustre. In the process known as frictional calendering a speed differential operates between the two rollers to impart a shiny, glossy, chintz-type surface finish. Embossing employs heat and pressure by passing cloth (typically a nonwoven cloth) between a heated engraved roller and a roller of softer material. Commonly, embossing is on light‑weight cloth where a logo of some kind is imparted. Embossing can give a seeming raised-surface effect, caused by passing a cloth under pressure between heated rollers, each with an embossed surface. With napping, traditionally applied to woollen cloth, but more widely applied to other cloth types by the mid-twentieth century, the fibre is raised by passing the cloth between rollers covered by hooked metallic needles. Examples include velvet- and flannelette-type cloths. A similar raised result is what is known as peach-skin finish applied to finely woven microfibre cloths. Brushing can remove loose fibres from a cloth’s surface, but the term ‘brushed’ cloth is used commonly where surface fibres are brushed or raised to give a nap surface with a soft handle. Sanforising, used mainly on cotton cloths, is a controlled mechanical shrinkage, without chemical applications, involving passing the cloth with the addition of steam between a series of belts and cylinders. Flocking (or flock printing, mentioned previously in section 7.4) is a process which involves either applying an adhesive to parts of a cloth’s surface and sprinkling short fibres over those parts or allowing the short fibres to adhere to the cloth’s surface through imposing an electrostatic charge; the former could be considered as a chemical finishing process and the latter as a mechanical finishing process. Shearing (also referred to as cropping) is a cutting process aimed at removing extra protruding fibres from a cloth’s surface. During cloth formation, high levels of stress are applied, and these build up and are held in the cloth. Compacting aims to accommodate these inbuilt stresses by releasing them in a controlled way and ensuring a stable or compact structure for future use. Compacting permits the cutting and application of the cloth to an end use without the possibility of further shrinkage during subsequent laundering. The sanforising process (mentioned above) is an example of a compacting procedure.
Evolution in the surface modification of textiles: a review
Published in Textile Progress, 2018
Ayoub Nadi, Aicha Boukhriss, Aziz Bentis, Ezzoubeir Jabrane, Said Gmouh
Lustre, smoothness and other surface effects on fabric are usually achieved by calendering. The fabric is inserted between heavy rollers varying in hardness, surface speed and temperature to achieve the desired, consistent fabric surface effects. Variations of calendering include embossing, schreinerizing and frictional calendering. Embossing is the production of a fabric pattern in relief by passing the fabric through a calender containing a rigid, heated and engraved metal roller and a soft or elastic roller. Schreinerizing is the technique for producing a lustrous fabric by passing it through rollers, one of which is engraved with very fine lines at an angle to the fabric being processed. In frictional calendering, fabrics are passed through a calender in which a rigid, highly polished and heated metal roller rotates at a higher surface speed than a soft roller to produce glazed or lustrous surface effects.