The caliper or thickness is one of the important basic physical properties of paper and paperboard. It is depends on refined stock, category of fiber, dryer temperature, load on press section and calendars, moister content, filler etc for a given basis weight. Thickness is related to bulk or dense of paper.
Uniform caliper or thickness is very important for mother roll building up, quality of paper, printing papers, condenser paper, saturating papers etc. If the caliper variant then it could be affect some fundamental properties including the quality of the paper as like bad formation, uneven drying, strength, stiffness, bad mother roll development, optical quality etc. Furthermore cutter machine have to face problem for bad mother roll building up. Caliper is most important for printing press; print quality and press runnability is affected by caliper variation. Hence controlling the caliper is very significant for a papermaker; he is always trying to keep optimum and uniform caliper.
How to increase the caliper of the paper
Caliper is affected by refining of the fiber; well refined or beaten of stock reduce the thickness. In addition consistency in the headbox also effect on it. So a papermaker always should check out the degree SR and consistency of the stock and should be keep it at optimum level.
Press and calendars nip pressure, number of press section, number of calendars and stacks are significant for caliper. If press and calendars load is reduce then increase it. On the other hand, if it is increase than decrease the caliper. Hence it should be used optimum press and calendars load.
Caliper is also affected by ash content or filler. If ash content is reduced then increase the thickness. Using of PCC as filler increased the caliper.
Short fiber pulp such as hard wood or straw pulp can reduce the caliper. Mechanical pulp such as BCTMP increases the caliper.
If first group dryer temperature differs then the caliper also differ. It should be low to increase the caliper.
Moisture content is another parameter for caliper. It should be kept standard level.
The measuring instrument is micrometer for thickness or Caliper of paper and expressed as mili-microns. The distance is taken in perpendicular under a pressure of 1 kg/ cm2.
Dear,
We are producing coated bleached board, and we use BCTMP pulp in filler or body. And caliper reduction of -10 occurs when product is sheet cut from sheeters. Mean to say, when product is produced its caliper like 300 microns, and when its sheet cut, its caliper reduced to 290 microns, would you plz help me out in this case. Thanks.
What’s reason of waveness of duplex board
Why can we have use the ultrazyme, and ultrpure. Chemical in hydrapulper . Give me chemical reason plz.
There are two factors explained. Beating/Refining and Machine adjustment to improve paper or board bulk.
On the other hand there are some artificial method to improve bulk.
1. Expancels are hydrocarbon filled micro-granules, which do expand multi-fold upon heating or drying process. They are incorporated along with furnish. See Akzanobel.
2. There are many chemical inputs, which make fiber dispersion making the paper fluffy. They are well known in tissue making.
After all, improving bulk is kitchen technology like making pakoda with basin and bi-carbonate pinch.
M.G.Panth
There are two factors explained. Beating/Refining and Machine adjustment to improve paper or board bulk.
On the other hand there are some artificial method to improve bulk.
1. Expancels are hydrocarbon filled micro-granules, which do expand multi-fold upon heating or drying process. They are incorporated along with furnish. See Akzanobel.
2. There are many chemical inputs, which make fiber dispersion making the paper fluffy. They are well known in tissue making.
After all, improving bulk is kitchen technology like making pakoda with basin and bi-carbonate pinch.
M.G.Panth