Understanding Paper Making Process: Fiber Orientation & Machine Direction

1. UNIT 1

2. INTRODUCTION OVERVIEW OF PRESENTATION • WHAT IS PAPER? • WHAT IS PAPER MACHINE? • WHAT ARE THE PROBLEM,S OCCUR ON PAPER MACHINE? • ORIENTATION OF FIBER • MACHINE AND CROSS DIRECTION • EFFECT OF WIRE AND FELT SIDE

3. WHAT IS PAPER? • PAPER IS THE WEB OF FIBERS WHICH IS IREGULARLY INTERWOVEN WITH EACH OTHER. • RANDOM NETWORK OF CELLULOSIC FIBER WHICH IS FORM ON PAPER MACHINE.

4. WHAT IS PAPER MACHINE? • PAPER MACHINE IS THE DEVICE ON WHICH OR PAPER GET FORM 0N IT . IN PAPER INDUSTRY PAPER MACHINE IS CALLED HEART OF PAPER INDUSRTY. • ON IT MANY ROLLS AND OTHER INSTRUMENTS LIKE HEADBOX, PRESS PART, DRYERS,CALENDERS,SIZE PRESS ARE PRESENT WHICH HELP TO FORM BETTER QUALITY OF WEB ON IT.

5. PROBLEM OCCUR ON PAPER M/C DURING WEB FORMATION • TWO SIDEDNESS • VARIATIONS IN PAPER M/C CAUSE VARIATIONS IN PAPER PROPERTIES • AFFECT THE APPEARANCE IF DIRT PRESENT IN SURROUNDING OF PAPER M/C • AND MANY MORE

7. ORIENTATION OF FIBER • WHAT IS FIBER? FIBER IS DEFINED AS THE SINGLE HAIR LIKE STRUCTURE WHICH COBINES TO FORM WEB OVER PAPER M/C ON PAPER. • THE GREATER ORIENTATION OF FIBER IN DIRECTION OF TRAVEL OF THE PAPER M/C. • THE GREATER ORIENTATION WHICH RESULT PARTIALLY FROM THE GREATER FIBER ALIGNMENT AND PARTLY FORM THE GREATER TENSION EXERTED ON THE PAPER IN THIS DIRECTION DURING DRYING.

8. CONTINUE • THE ORIENTATION OF FIBER ARE GREATER IN M/C DIRECTION AS COMPARE TO CROSS DIRECTION • ALL THE PROPERTIES EITHER PHYSICAL CHEMICAL OR OPTICAL ARE AFFECTED AND RELATED TO THE ORIENTATION OF THE FIBER. • A NEW METHOD FOR MEASURING THE DEGREE OF FIBER ORIENTATION IS BY X RAY. THIS METHOD IS BASED ON THE FACT THAT THE MAJORITY OF THE FIBRILLS ARE LINNED UP IN THE FIBER DIRECTION AND HENCE PRODUCE AREA IN X RAY DIAGRAM WHICH INDICATE THE POSITION OF FIBER IN PAPER.

9. EFEECT OF WIRE AND FELT SIDE ON PAPER • PAPER HAS 2 SIDES • THE WIRE AND THE FELT SIDE . • THE WIRE SIDE IS THE SIDE OF THE PAPER WHICH IS IN THE CONTACT WITH WIRE AT THE TIME OF THE SHEET FORMATION. • THE OTHER SIDE IS FELT SIDE. WHICH IS NOT IN CONTACT WITH WIRE. • THE WIRE SIDE IS ROUGHER DUE TO PATTERN CAUSED BY WIRE MARKS. • PAPER IS GENERALLY OPEN ON THE WIRE SIDE AND CLOSED OR FINER TEXTURED ON THE FELT SIDE.

10. CONTINUES • ALL THOUGH ALL THE PROPERTIES OF PAPER ARE AFFECTED BY THE FORMATION OF THE FIBER BUT SOME OF THEM ARE • SMOOTHNESS (MORE IN FELT SIDE) • POROSITY (MORE IN WIRE SIDE) • FORMATION (BETTER IN FELT SIDE THAN IN WIRE SIDE) • GLOSS AND BRIGHTNESS (MORE IN FELT SIDE) • INK ABSORBENCY (MORE IN WIRE SIDE)

11. MACHINE DIRECTION AND CROSS DIRECTION • THE DIRECTION OF THE PAPER IN THE DIRECTION OF THE TRAVEL OF THE PAPER MACHINE IS CALLED MACHINE DIRECTION. OR • THE GRAIN DIRECTION IS KNOWN AS MACHINE DIRECTION. • PERPENDICULAR TO THE MACHINE DIRECTION IS KNOWN AS CROSS DIRECTION. • THE PROPERTIES WHICH ARE AFFECTED BY THE MACHINE DIRECTION AND BY THE CROSS DIRECTION ARE AS FOLLOW

12. M/C DIRECTION AND CROSS DIRECTION

13. CONTINUE • TENSILE STRENGTH (GREATER IN THE MACHINE DIRECTION) • FOLDING STRENGTH (GREATER IN M/C DIRECTION) • TEARING STRENGTH (GREATER IN CROSS DIRECTION) • STIFFNESS (GREATER IN THE M/C DIRECTION) • BASIS WEIGHT (GREATER WEIGHT VARIATION OBSERVED IN THE CROSS DIRESS DIRECTION THAN IN MACHINE DIRECTION)

14. UNIT 2

15. BASIS WEIGHT DEFINITION:- The weight of paper per unit area is defined as basis weight. • This can be expressed as weight in grams per square meter (GSM) • This can also be expressed as the pounds per 1000 sq. ft.

16. Generally paper is sold on weight basis. Also paper is defined as per unit of area rather than per unit of volume. • The area is more important than volume as paper is used in sheet form.

17. INSTRUMENTS FOR MEASURING BASIS WEIGHT • QUADRANT SCALE a. Quadrant type ( Thwing ) b. Pendulum type ( Schopper ), ( Cady ) c. Lever type ( Toledo )

18. QUADRANT SCALE

19. QUADRANT SCALE • Quadrant scale is a specially graduated scale which give the result directly in gram per meter square. • Sample size of paper is 40*25cm2. • The template size is 20*25 cm2.

20. 2. β-RAYS BASIS WEIGHT GAUGE • It is an interesting new device for measuring the basis weight of paper continuously and automatically in β-rays basis weight gauge. • The paper absorb β-rays in direct proportion to it’s mass so that the response of the detector to the rays passing through the paper is the function of the basis weight. • The paper travel through a measuring head which consist of a β-rays emission chamber below the sheet and an ionization chamber above the sheet that detects the desired weight.

21. Sample conditioning standards • Time = 4 to 12 hr. ( for normal paper ) • Relative Humidity = 50 % • Temperature = 23 ± 5°C For certain treated paper and heavy paperboards may require 24 to 48 hours for conditioning till constant weight is obtained.

22. Basis weight of different grades of paper

23. THICKNESS/CALIPER • Caliper or Thickness For a given basis weight, determines how bulky or dense the paper is. • A well beaten/refined pulp, short fiber pulp such as hard wood or straw pulp, highly filled or loaded paper will show lower thickness for given basis weight. • Thickness or Caliper of paper is measured with a micrometer as the perpendicular distance between two circular plane parallel surfaces under a pressure of 1 kg/

24. Thickness affects nearly every physical, optical & electrical property of paper. It is highly important in case of filling cards which should not exceed the required thickness avoid taking up variable space in filling cabinet. • Thickness is important in case of book paper, since it affect the opacity of paper and amount of impression received on printing press. A typical 80 pound coated book paper will normally caliper about 0.004 inch with a variation of about 0.00025 inch.

25. CALIPER MICROMETER

26. Thickness is factor in the performance of condenser paper, bloating paper, wrapping paper and many other paper grades. • Capacitor paper is made to specification of to 10000’s of an inch ± 11 hundred tolerance. • Craft linear board is sold on the basis of caliper and there for it is important in the mfg. of this grade to maintain maximum caliper consistent with the desired physical properties.

27. Caliper is also very important in folding book board where it is the most important variable affecting thickness. • The thickness gauge tends to ,measure the thickest part of the paper because of the relatively large diameter of the micrometer (1/4 inch). The measured caliper usually higher then the actual caliper because the anvil of the thickness gauge tends to bridge over the high spots of the paper this can result in a substantial difference between measure and true value in the case of rough finish paper board.

28. Burst and bursting strength 1. Burst-- Rupture of the paper is called burst 2. Bursting strength-- Bursting strength of material is defind as the maximum Hydrostatic pressure required to Produced rupture of the material . When a controlled and constantly increased pressure is applied through a rubber diaphragm to a circular area, 30.5 mm dia.

29. 3. Scope-- This method is designed to measure the max. bursting strength of paper and paper product having bursting strength of 50 KPA up to 1200 KPA and in the form of flat sheet of up to 0.6 mm thick. It is not intended for use in testing fiberboard linearboard, hardboard that tend to cut the thin rubber diaphragm of the bursting tester.

30. 4. Unit-- 1. Pounds per square inch 5. APPARATUS-- 1. Mullen Bust tester 2. Caddy 3. Ash croft 4. Schopper Dolen

32. 6. Factor affecting bursting strength 1. Fiber length, inter fiber bonding. 2.increase beating, Increases the bursting strength. 3. Surface sizing affects the bursting strength.

33. 7.Procedure • The specimen should be held b/w two annular clamps under sufficient pressure to minimize slippage. • The sample is clamped b/w the lower clamping plate and pressure cylinder so that before the paper sample is stretched by pressure underneath. • The paper starts to rupture when pressure is applied. • Note the reading at that point when paper is ruptured.

34. 8. Uses of bursting strength-- 1. It is quite important in bag papers. 2. It is important in wrapping papers. 9. Burst factor-- Burst strength in gm/cm² per Substance in gm/m²

35. 10. Density Density related to the porosity, rigidity, hardness strength of the paper. Unit= kg/m³ Density formula ( Basis wt. In GSM/Thickness in cm)0.0001001 Relation between density and sheet property Clark found that burst and tensile strength are linearly perportional to density. Density greaterly effect the optical properties. Inc.beating has no effect on tensile strength. Filler Increase The density but Decrease the strength

36. 11.Factor affecting density 1.Density which is obtained as the ratio of weight the thickness before paper furnished to remove surface irregularities 2.In the case of box board there is a true Density with increase in caliper

37. PAPER PROPERTIES A PRESENTATION ON POROSITY AND FORMATION

38. Porosity • In the following presentation paper porosity actually means air permeability. • A measure of the extent to which a paper surface will allow the penetration of a gas or liquid, such as air or ink, through its surface. The nature of paper is such that the bonding of the paper fibers produces many tiny air passages through out the paper, which can either be completely submerged in the paper.

39. Porosity can be measured in the laboratory or online on the paper machine. • In the following, the measurements are air flow values like in Bendsten (ml/min) or time values for a constant air volume like in Gurley(s). • Notice that a smaller number in seconds means a higher air flow and porosity. • sizing ,coating ,calendaring and super calendaring all also work to seal and/or compress surface fibers, reducing the paper's porosity.

40. If the air-permeability of the paper is too high (i.e. low Gurley Densometer value).Papermakers know intuitively that they can solve this problem by greatly increasing the basis weight.

41. Online Porosity:- • The latest online porosity analyzer has a strong and durable structure avoiding mechanical damages during machine breaks. The sensing element is specially coated to minimize friction, dusting and dirt build-up on the web contacting surface.

42. Unit :- • The units of porosity is ml/min. Instruments:- • Bend ten smoothness and porosity tester. • Gurley densometer. • Williams tester. • Permeometer

43. MEASUREMENT:- • In routine paper testing porosity is generally measured by the resistance of paper sample of given dimension to the passage of air under standardized condition of pressure, temperature, and relative humidity. This resistance is measured by Gurley or SPS tester. • This tester measured the time of flow of the standard volume of air (usually 100cc) through a standard area (usually 1sq. in.) of the paper under uniform light pressure. • Air is forced through the paper by pressure resulting from the weight of the inner cylinder floating freely in an outer cylinder partly filled with light oil

44. In densometer paper is clamped on the top of the inner cylinder, whereas the paper is clamped on the base of the SPS tester on the top of a perforated plate. • The instruments are equipped with an elastic rubber (Thiokol) gasket to prevent air leakage laterally across the surface of paper. • This gasket is a part of the densometer but must be inserted in the SPS tester when porosity test are being made. The moveable inner cylinder is graduated in units of 50ml, the volume air transmitted is read on the gage. • The time for the passages 100cc of air is taken after the cylinder has been released and attained a steady downward movement. The apparatus should be tested periodically for leakage by testing smooth, non – porous material such as metal foil: leakage exceed 10ml of air per hour.

45. POROSITY OF VARIOUS GRADES OF PAPER

46. Importance of Porosity • Porosity is a paper property of direct importance in writing printing paper, since it is a factor in absorption of ink. • It is definitely related to oil resistance and hence is an important property of grease an proof and oil resistance paper. • Porosity is an extremely important property of saturating papers. • Porosity is very important in bag papers, filter paper. • It is an important property of coating of a raw stock for pigmented coated papers where it affects the adhesion of adhesive.

47. Fig:-Bendsten Smoothness And Porosity tester

48. Formation:- • The manner in which the fibers of a sheet of paper or board are distributed, disposed and intermixed to constitute the sheet. • Formation is an indicator of how uniformly the fibers and fillers are distributed in the sheet. • Formation plays an important role as most of the paper properties • These will affect properties like caliper, opacity, strength etc. Paper formation also affects the coating capabilities and printing characteristics of the paper.

49. Paper formation also affects the coating capabilities and printing characteristics of the paper. • A poorly formed sheet will exhibit more dot gain and a mottled appearance when printed. • There is no standard method or unit to express formation • However when holding paper up to alight source, a well formed sheet appears uniform while a poorly formed sheet has clumps of fibers giving a cloudy look. • It is physical property of paper. • Formation is affected by the transparency of the paper since in general the more transparent the paper, the more readily poor formation shows up. for ex. Waxpaper generally appear more poorly formed than the same paper.

50. MEASUREMENT OF FORMATION:- • An instrument consisting of a photo electric cell which scans the under Neath side of the paper. • While a small beam of control intensity is projected on the upper surface of the paper the paper is moved at high velocity through the tester. • So that the amplitude and frequency of variation in transmitted light can be measured by the photoelectric cell.