- Calender
:"This article is about a device for smoothing paper. For the method of timekeeping, see
calendar . A calender (or kalandar) is also an order ofdervishes in Turkey and Persia."The calender is a series of hard pressure rollers at the end of apapermaking process (on-line). Those that are used separate from the process (off-line) are also called "supercalenders". The purpose of a calender is to smooth out thepaper forprinting andwriting on it, and to increase the gloss on the surface.The word “calender” itself is a derivation of the word "kylindros", the Greek word for “cylinder”. [http://www.merriam-webster.com/dictionary/calender Merriam-Webster definition] ]
In the past, the paper sheets were worked on with a polished
hammer or pressed between polishedmetal sheets in a press. With the continuously operating paper machine it became part of the process of rolling the paper (in this case also called [http://glossary.ippaper.com/default.asp?req=glossary/term/2525&catitemid= web paper] ). The pressure between the rollers, the "nip pressure", can be reduced by heating the rolls and/or moistening the paper surface. This helps to keep the bulk and the stiffness of the web paper which is beneficial for its later use.Modern calenders have "hard" heated rollers made from chilled
cast iron orsteel , and “soft” rollers coated withpolymeric composites. This widens the working nip and distributes the specific pressure on the paper more evenly.Other materials
Calenders can also be applied to materials other than paper when a smooth, flat surface is desirable, such as cotton, linens, silks, and various man-made fabrics and polymers such as
vinyl and ABS polymer sheets, and to a lesser extentHDPE ,Polypropylene andPolystyrene .
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