Paper. Standards & Measurements. sappi

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1 Paper Standards & Measurements sappi

2 Sappi is committed to helping printers and graphic designers use paper in the best possible way. So we share our knowledge with customers, providing them with samples, specifications, ideas, technical information and a complete range of brochures. Find out more on our unique web site

3 Paper Standards & Measurements Content l Introduction 3 ll Paper Specification 4 Basis weight 4 Thickness / Caliper 4 Specific volume 4 Relative humidity 4 Vl Absorption 11 Water absorption Cobb 11 Oil absorption Cobb-Unger 11 Ink absorption / Set-off 11 Water absorption Drop test (Prüfbau) 11 Ink repellence IGT 12 Contact angle measurement 12 Penetration Dynamic Analyzer (PDA) 12 III Optical Properties 5 Gloss 5 ISO-Brightness 5 CIE-Whiteness 6 Shade (colour) 6 Opacity 6 Metamerism 6 Fluorescence 6 Yellowing 6 VlI Others 13 ph value 13 Ash content 13 Mottle test 13 Ink rub resistance 14 Cracking test 14 VIIl List of Standards and Measures 15 IV Surface Properties 7 PPS roughness 7 Smoothness 7 Surface roughness (laser profile) 7 Picking resistance 7 IGT 7 Prüfbau 7 IX Concluding remarks 16 X Table of recommended units 17 XI Table of conversion factors 18 V Strengths 8 Tensile strength and breaking length 8 Elongation (stretch at break) 8 Tearing resistance 8 Residual strength 9 Bursting strength 9 Stiffness (rigidity) 9 Scott Bond 10 Blister test 10 1

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5 l Introduction This brochure is a small summary of the very extensive publications of DIN and ISO standards. It has been produced to help explain the most important standards and units without complicated mathematical formulas and with simple words. The paper properties are arranged into different groups, so that the emphasis in the requirements of the paper becomes clear. Therefore some overlaps cannot be avoided. 3

6 ll Paper Specification A paper specification is a list of characteristics with appropriate measured values, which the paper has to fulfill. The measured values are indicated with their tolerances. A specification is necessary, since this shows the requirements of the customer and forms the basis, that always the same paper is supplied. In order to come to a specification, one must know the intended purpose and the requirements of the paper. Discussions with the customer or consumer are the correct way to co-ordinate the requirements of the paper and the possibilities in paper production. Basis weight ISO 536 The weight in g/m 2 is understood by the basis weight of a paper under conditioned circumstances. The entire mass is the sum of fibrous materials, fillers, process materials and water. The picture above shows the most important optical and physical characteristics, in so-called Datasheets are listed. These can request or with your personal partner receive you at any time in the Internet. Relative humidity Tappi 502 The relative humidity indicates how many percent of the maximum possible water vapour portion, at a certain temperature is actually in the air (i.e. between the sheets of a stack or the windings of a reel). Thickness / Caliper ISO 534 The thickness of a paper is measured between two even plates, which are adjustable with a defined pressure. Because of the compressibility and the inhomogeneity several measurements have to be carried out and the results averaged. The thickness of a paper is dependent on grammage and specific volume. Specific volume ISO 534 The thickness is expressed in micrometers (μm). To compare the thickness of papers with different basis weights, the specific volume is used. This is the thickness to which the basis weight of 100 g/m 2 refers. This calculation is carried out according to the formula: Thickness (μm) divided by the basis weight is the specific volume (cm 3 /g). L&W Micrometer 4

7 lii Optical Properties The first impression of a paper is its colour, its whiteness and its gloss. The appearance of the paper is of course important when it is sold, but the optical properties are also important when the paper is printed on. In order to be able to manufacture paper with the right optical properties, pulp and coating raw materials, paper technologists must have access to good measurement methods. The optical characteristics of the paper are affected by the measurement of reflection, absorption or transmission of light which strikes a sheet of paper. Whiteness and shade of the paper do not have direct influence on the printability but have an influence on the printed result. Colour printed on bright white underground results in another impression than printed on other white undergrounds. ISO-Brightness ISO 2470 The brightness is a measure for the reflection of blue light of the paper expressed in a percentage in comparison with an ultimate reference brightness standard (IR3 standard). There are three brightness values for fluorescent papers: ISO-brightness under C-light, D65-brightness under D65 light and brightness with fluorescence eliminated. The higher the brightness value, the brighter the paper is. Papers with optical whitening agents show a peak in the blue reflection. This addition of blue reflection causes the sample to appear whiter to the observer and gives higher ISO-brightness and D65-brightness values. The ultraviolet energy level of the illumination must be adjusted using a fluorescent calibration standard. The ISO standard used for the colour management in the graphic arts industry provides a colour-correct reproduction with the consideration of the paper type. Gloss ISO (DIN) ISO (Tappi) A calendered, coated or varnished paper has a high proportion of direct reflection, which is commonly called gloss. Gloss is an important characteristic in the production of coated papers. The gloss makes paper look elegant and the property is therefore important for advertising print. Gloss is measured with special instruments where the sample is illuminated with parallel light at a certain incidental angle. Fixed optical geometries, incidental and reflection angles of 75, 60 or 20 degrees, are usually used. A specific geometry and angle is used, based on paper quality and gloss level. The following gloss standards are common: DIN 45 or 75 and Tappi 75 or 20. DIN standard and/or low angle are used for (ultra) high gloss levels. Gloss can also be measured on a printed area and is called print gloss. L&W Gloss Tester 5

8 CIE-Whiteness ISO 2470 Whiteness is a subjectively perceived property. Most people consider that it increases when the material has a slightly blue tone. It is thus clear that whiteness in some way is an aspect of colour perception, and that any measurement of whiteness must be based on colour management. Yellowing DIN 6167 Degree of yellowing / discolouration of paper exposed to daylight or heat, after a specified period of time. A test piece is exposed for a specified time to UV light or heat. Colour measurements at specific time intervals describe the yellowing / discolouration. The degree of yellowing is expressed in a yellowing number. Shade (colour) ISO 5631 Shade of a paper is the colour of a paper. The colour is described as blue, green, yellow or red or as a mixture of these colours. The colour can be described according to intensity and saturation. There are several different systems in use, but most common for the paper industry is the CIE L* a* b*. Opacity ISO 2471 The opacity is a measurement for the light transparency degree of the paper, expressed in a percentage in relation to the reflected light. Paper which lets a lot of light through is transparent; paper which lets less light through is opaque. The higher the value, the more opaque the paper is. Metamerism Metamerism is the condition in which two colours can appear identical under certain light sources but exhibit clear differences in other light sources. This occurs because the reflective/reflection curves of the metameric colours are not the same/alike over the whole spectrum. Fluorescence If a colour becomes more optically intensive under a certain light source it is due to the effect of fluorescence. This occurs when parts of the incident light are reflected in other wavelengths. The impact of fluorescence is shown by the optical brighteners used in many papers as they convert UV light into visible light. Elrepho 6

9 IV Surface Properties Paper is a surface product, its surface determines the visual impression and the feel. Beyond that, printing techniques, converting techniques and application determine the characteristics of the paper surface. PPS roughness ISO The geometric form of a paper surface is defined as deviation from the ideal dead level. The more the surface approaches the ideal level, the smoother the paper is. The measuring method (PPS) is based on the measurement of the air leakage between the paper surface and an even measuring head. In case of the PPS roughness, the depth of the pores is measured by a defined circle. The higher the measured value is, the rougher the paper surface is. Smoothness ISO 879/-2/3 und ISO 5627 Definition and measuring method are comparable with those used for roughness. Depending upon measuring technology either the time is measured in which a certain amount of air is used (Bekk and Gurley) or airspeed is measured under a constant pressure (Bendtsen or Sheffield). Apart from the air flow measurement principles there is also the optical smoothness measurement according to FOGRA and IGT method for determination of print smoothness. Picking resistance The picking resistance of a paper is the strength of the paper surface (Z-direction). In the offset printing process there are forces on the paper surface caused by splitting of the ink (tack) and adhesion forces of the blankets. Individual fibers, coating particles or whole surface areas can be pulled out. The picking resistance can be determined according to different methods: IGT ISO 3783 The IGT and Prüfbau picking tests show rather good correlations with picking demands in the offset printing process. The principle of the test methods is to simulate as much as possible the print conditions. With the IGT method oils with different viscosity are used in combination with accelerated speed. The selection of a combination of oil and speed is dependent on the kind of paper (LWC, WFC etc.). Prüfbau With the Prüfbau-test special test inks or commercial inks can be used to perform a picking test. It is also possible to pre-wet the paper with fountain water to determine the wet pick. The adjustable parameters such as pressure, speed, printing roller and time interval must be taken from the test provisions and be tuned with the respective type of paper and its application. Surface roughness (laser profile) By use of a laser profile device it is possible to make a 3D topographical roughness profile of the paper surface. Every component s surface has some form of texture which varies according to its structure. These surfaces can be broken down into three main categories: Surface roughness, Waviness and Form. With this measurement it is possible to analyze defects of the paper surface related to the paper machine. Prüfbau 7

10 V Strengths The strength of paper plays an important role during production but especially at converting of the paper. The strength is in many cases also important for the use of paper. A paper, which is produced as a reel is subject to a tensile force in linear direction, a paper which is produced as a sheet is subject usually to a tensile force in transverse direction. Depending on the forces on the paper there are test methods, which can objectively determine if the paper s strength is sufficient for these demands (forces). Tearing Tester Tensile strength and breaking length ISO The testing of the paper on tensile strength takes place via tear test under a defined increasing force. The measured tensile strength value is the quotient of the force (N) at the moment of break and the width of the test strip. The tensile strength index is the quotient of the tensile strength and the grammage (g/m 2 ) of the paper. Tearing resistance ISO 1974 The mean force required to continue the tearing of an initial cut in a single sheet of paper is expressed as the internal tearing resistance. If the initial slit is made in the machine direction, the result is given as machine direction tearing resistance and similarly for the cross machine direction. The breaking force (N) and the grammage are the basis for calculating the breaking length. The breaking length is the length of a strip of paper with a defined width, when, freely suspended, it tears due to its own weight. Elongation (stretch at break) ISO The elongation at rupture defines the stretch of a paper in percentage (%) at the time of tearing in relation to the unloaded length. The elongation at rupture is simultaneously measured with the breaking force. From the breaking force and elongation graph the elasticity module can be calculated. This elasticity module is related to the dimensional stability of the paper in different printing and converting processes. Tensile Tester 8

11 Residual strength FOGRA Residual strength is an important characteristic for web offset papers. In web offset the paper is printed, heated and folded. During this process the paper should have a specific residual strength to prevent web breaks and breaks on the fold. Under standardized circumstances a paper is heated and folded. Directly afterwards the tensile strength of the test piece is determined. A general method for residual strength is the FOGRA method. With this method the residual strength of the paper should be higher than a minimum value of 0.67 kn/m. Bursting strength ISO 2758 The bursting strength is expressed as the maximum uniformly distributed pressure, applied at right angles to its surface that a single sample piece can withstand under test conditions. The Burst index is the bursting strength divided by the grammage. Bursting Strength Tester Stiffness (rigidity) ISO 5628 The stiffness is an important characteristic of the paper, because it has substantial influence on the runability properties during the printing process and on the requirements for converting (folding, creasing etc.). Stiffness is defined as resistance against bending in the elastic area of the paper. Beside grammage and thickness there are other items which have influence on the stiffness, such as choice of raw materials, refining degree of the fibers, quality and amount of filler and moisture content. The extent of the bend follows the laws of mechanics, which means the paper is not damaged when stretched on the outside and compressed on the inside. There are different methods available to determine the stiffness but the most used method in the paper industry is the 2-points load method. With this method the force needed to bend a rectangular test piece to a specified angle is measured. The stiffness in machine direction and cross direction are the key factors. 9

12 Scott-Bond Tappi T 569 ZDT Tappi T 541 Internal bond strength (paper s strength in its thickness direction) is an important characteristic during printing and converting processes. Internal bond strength is the maximum load that single ply or multiple paper or boxboard can withstand when loaded with a force directed at right angles to the surface of the sample material. The paper s ability to withstand these forces depends on factors such as choice of pulp, degree of beating and refining, paper machine settings and choice of additives. The Z-directional tensile and Scott Bond tests are different methods. The ZD-tensile measures the maximum force to split the sample at a low standardized test speed perpendicular to the test surface. The Scott Bond method measures the energy needed to split the sample at a speed several thousand times higher. Internal bond is related to several phenomena during printing and converting such as delaminating, blistering, creasability etc. Blister test Scott-Bond Tester With the Blister test the drying section of a HSWO printing press is simulated. The blister oil test has proven to be a good test to determine the blister resistance in practice. The paper is put in an oil bath with a specific temperature and the water located in the paper evaporates, just as happens in the drying section of the HSWO printing press. Blistering can occur if the temperature is too high, the internal bond too low or the vapour permeability too low. Printed areas with a high coverage of ink ( %) are more sensitive for blistering. Papers used for HSWO should show no blistering at a temperature of C or F. 10

13 Vl Absorption Oil absorption Cobb-Unger FOGRA Types of paper for offset printing should have a certain absorption to give the ink a good adhesion and to store the fountain water (temporarily). The absorption level should not be so high that printing ink and fountain water show through the paper. The absorption is an important property of the paper during the printing process and is a crucial factor for paper-ink-fountain water interaction studies. Water absorption Cobb ISO 535 Dependent on the intended purpose, different measuring methods for the determination of the water absorption ability were developed. An old method is with the help of a pulling feather/spring to apply a coloured ink on the paper with a specific increasing width and observe if the ink spreads out or shows through. With the ink swimming test the measure of gluing is likewise tested. Both testing methods are limited to printing and writing papers. For papers which are printed in offset the absorption is often determined with the Cobb test. The water absorption is determined by measuring the amount of water, which is taken up by the paper within a specific time. The Cobb test gives only reliable values, if the paper is not fully soaked through with water. The Cobb test can also be used for the measurement of oil absorption instead of water and is called the Cobb-Unger. Ink absorption / Set-off The set-off of paper describes the absorption of ink on the paper. The speed of absorption is determined by the time that the ink needs to penetrate into the paper. For the offset process this property is very important. An absorption which is too slow, may result in smearing because the ink does not dry fast enough. An absorption which is too fast, may result in a reduction of the dry ink properties. The set-off of paper can be measured with a test printing machine like Prüfbau or IGT. A sample is printed with a standard ink. After several time intervals, a part of the printed sample is countered against a blank counter sheet of the same paper (top on bottom in order to simulate a pile). The density of the transferred ink of each area on the counter sheet is measured and plotted against time. The shorter the time from high ink transfer to no ink transfer of the counter sheet the faster the set-off. Water absorption Drop test (Prüfbau) The drop test is carried out using the Prüfbau printing machine. A drop of a defined Isopropylalcohol solution is applied to the paper sample by means of a micro-pipette and the paper is immediately printed with an ink. The ink densities in the pre-wetted and dry printed areas are measured. The ink density in the pre-wetted area is expressed as a percentage of the ink density in the dry printed area. The higher the value, the lower is the ink repellence of the paper. Cobb Sizing Tester 11

14 Ink repellence IGT If the flow rate of fountain solution is high and/or the paper has poor water-absorbing characteristics, the film of fountain solution on the surface of the paper results in repulsion of the ink in the following printing unit. Depending on the extent of the repulsion, solid areas can show an uneven printout. The ink repellence test is carried out using the IGT test-printing machine. Dampening is performed using an engraved steel roller dampened with fountain solution. The printing unit of the IGT tester is situated below the dampening unit, which allows the first section of the paper strip to be printed dry. The second section of the paper strip is printed after dampening and is designated as the first interval. There is a time interval of 0.05 seconds between wetting and printing. The printing densities of the solid area (dry printing) and the pre-wetted area are measured. The mean value of the dampening interval is expressed as a percentage of the mean value of the solid area. The higher these values are, the lower is the ink repellence of the paper. Penetration Dynamic Analyzer (PDA) With this test it is possible to measure process relevant parameters of paper, coating colours or chemicals like glue and ink with the aim of predicting printability, glueability and ability for coating. A paper sample is brought into contact with liquid in a measuring cell. From the moment of liquid contact, it is radiated in the Z-direction with high-frequency low-energy ultrasonic signals. These signals are received by a highly sensitive sensor before they are processed in the device and transmitted to a personal computer. The main advantage of this method compared to other methods is that the penetration dynamics can be tracked in real time with millisecond time resolution. Contact angle measurement Tappi-558 With determination of the absorptive capacity of paper for liquid it is necessary to define clearly, which liquid it concerns, how long the time of contact will be and under which conditions the test is implemented. In most cases where a liquid droplet is applied to a solid material, an angle is formed at the point of contact between droplet and solid, the so called wettability angle or contact angle. This contact angle is an indication of the wetting performance of liquids applied to solids. This contact angle must be determined immediately, because the liquid could penetrate rapidly into the pores of the paper. Many printing inks, oils, paraffins and similar products have rather a low surface tension and are spreading immediately on the paper surface. Contact angle measurements and wetting studies can be performed using an automated contact angle tester. Drop test: Paper with a good water absorption Drop test: Paper with a bad water absorption 12

15 Vll Others ph value ISO 6588 The ph value in the data sheets defines the ph value of the surface. The ph values are indicated on a scale from 0 to 14. The measuring value 7 marks the neutral point which corresponds to distilled water. Values below 7 refer to increasingly acid, values above 7 stand for increasingly alkaline. Papers should be close to, if possible, next to the neutral area or in the slightly alkaline range to have ideal requirements for printing and further treatment. Ash content ISO 2144 The ash content is the remaining residue as percentage of dry paper after ignition at 900 C. The ash content is the total of inorganic material, like carbonate, kaolin etc. in the paper (including filler). Fillers have an important influence on the paper quality (for instance opacity) and are dosed with care depending on the application of the paper. Mottle test Mottling is the uneven print appearance, mostly in solid areas: small dark and light areas in the surface of paper (board) caused by ink, paper or printing press. Mottle is influenced by many parameters: e.g. ink, colour sequence, construction of printing press, speed, rubber blanket and fountain water. Variations in the surface characteristics such as absorption and smoothness play an important role regarding mottle and are caused by the production process and the components within the paper. There can be three kinds of mottle: Backtrap mottle Ink applied to paper surface on a preceding printing unit of a multi-colour press will split onto the blanket in a subsequent unit and then be re-deposited onto the next sheet. If this occurs unevenly, the print can become mottled. This backtrap mottle can be simulated on a test printing machine by printing the paper and countering the paper in pre-defined times against a clean blanket reel. Water interference mottle Water transferred to paper surface on a preceding printing unit of a multi-colour press should be absorbed by the coating before it reaches a subsequent printing unit. If it is not absorbed it will prevent even transfer of the ink. A mottled print can result. The method IGT ink repellence (see chapter VI Absorption) is used to test this phenomenon. Midtone mottle (screen mottle) This is an uneven print in 30 60% screens, caused by differences in the scattering and absorption behaviour of base paper and/or coating. This effect can occur in one colour printing and even in case of perfectly formed dots of equal density (optical effect). Midtone mottle can be evaluated by printing a screen with the test printing machine or with help of a plastic screen which is put on top of the paper. The level of screen mottle can be evaluated visually or with help of image analysis. 13

16 Ink rub resistance Prüfbau Rubbing is the effect of repeated relative shifting of two touching surfaces under a certain amount of pressure. The measure of resistance of a printed material to this rubbing effect is known as ink rub resistance. Ink rub resistance can be determined with the Prüfbau ink rub tester. 48 hours after printing the ink rub resistance is visually evaluated. It is also possible to evaluate the ink rub resistance with a spectrophotometer or with image analysis. Cracking test DIN After the printing process the paper is mostly converted to brochures, books, maps etc. During converting when the paper is folded, cracking of the coating can occur at the folds. Papers below 170g/m 2 are directly folded, whereas papers equal or above 170g/m 2 are creased before folding. Folding can be carried out with the Fogra folding tester. Fold is visually evaluated for cracking. The creasability of a paper is tested with a special machine, which has a creasing knife and different rules. Papers which can be creased within a wide range (combinations depths and widths) without showing faults, have a good creasability level. Papers that can only be creased without showing faults within a small range have a bad creasability level. 14

17 Vlll List of Standards and Measures Selection of ISO/DIN/TAPPI and FOGRA test methods Unit Europe US Paper Specification Basis weight g/m 2 ISO 536 Tappi T 410 Thickness / Caliper μm ISO 534 Tappi T 411 Specific volume cm 2 /g ISO 534 Tappi T 500 Relative humidity % Tappi 502 Tappi T 502 Optical Properties Gloss % ISO and 2 Tappi T 480 ISO-Brightness % ISO 2470 Tappi T 452 CIE-Whiteness ISO Tappi T 562 Shade ISO 5631 Tappi T 524 or T 527 Opacity % ISO 2471 Tappi T 425 Metamerism Fluorescent Yellowing DIN 6167 Surface Properties Roughness PPS μm ISO Tappi T 555 Smoothness Bekk sec. ISO /3 and ISO 5627 Tappi T 479 Surface roughness (laser profile) Picking resistance IGT ISO 3783 Tappi T 514 Prüfbau Strengths Tensile strength and breaking length kn/m km ISO Tappi T 494 Elongation % ISO Tappi T 494 Tear resistance mn ISO 1974 Tappi T 414 Residual strength kn/m FOGRA Bursting strength kpa ISO 2758 Tappi T 403 Stiffness mn.m ISO 5628 Tappi T 556 Scott Bond / ZD Tensile J/m 2 kpa Tappi T 569 Tappi T 541 Tappi T 569 Tappi T 541 Blister test Tappi T 526 Absorption Water absorption Cobb g/m 2 ISO 535 Tappi T 441 Oil absorption Cobb-Unger g/m 2 FOGRA Ink absorption / set-off test (Prüfbau) Water absorption (Drop test) Ink repellence IGT Contact angle measurement Tappi T 558 Tappi T 558 Penetration Dynamic Analyzer Others ph-value ISO 6588 Tappi T 509 Ash content % ISO 2144 Tappi T 211 and T 413 Mottle test Ink rub resistance Cracking test DIN

18 lx Concluding remarks The contents of this brochure result from extensive research work, closely linked with practice and with practical experience. We would like to take this opportunity to thank the following company for their support and assistance Lorentzen & Wettre KISTA, Schweden All statements and information are correct to the best of our knowledge. All liability for losses associated with suggestions given in this brochure is excluded, regardless of the legal basis. The right is reserved to make technical changes to our grades in the course of further development. All rights reserved 2007 by Sappi Europe SA Imprint Sappi Fine Paper Europe Text and Editing: Herrmann Nax, Maurice van Duuren 16

19 X Table of recommended units We hope this list of most frequently referred units and properties within this catalogue will be a useful tool for all who are involved in the pulp and paper field. Recommended units are from the International Standard, ISO Property Adhesion on strength of glue bonds of corrugated fiberboard Recommended unit or method of expression kn/m Air permeance μm/(pa s) Air resistance (Gurley) s Apparent bulk density g/cm 3 Apparent sheet density g/cm 3 Ash % (mass/mass) Bending stiffness μm, mnm, Nm Bending stiffness index Nm 7 /kg 3 Box compression resistance BCT kn Breaking length km Bulking thickness μm Burst energy absorption Jlm 2 Burst index kpa m 2 /g Bursting strength kpa Compression resistance SCT kn/m Compression resistance SCT index knm/kg Conductivity of extracts ms/m Dimensional change after immersion in water % Dirt and shives in pulps Drainability of pulp "CSF" and Schopper-Riegler Edgewise crush resistance Electric strength Flat compression resistance Flat crush resistance FCT (corrugated board) Flat crush resistance of laboratory fluted corrugated medium Fold number, double folds Folding endurance 10 2 (number of specks)/kg numerical value kn/m kv/mm kpa kpa N numerical value log 10 (number of folds) Fracture toughness J/m Fracture toughness index Jm/kg Friction coefficient N/N Gloss % or numerical value Grammage g/m 2 Hygroexpansivity % Ink absorbency K and N K and N units Light absorption coefficient m 2 /kg Light absorbing power numerical value Property Light scattering power Light scattering oefficient Moisture content or dry matter content Opacity % Picking velocity, IGT Puncture resistance Recommended unit or method of expression numerical value m 2 /kg % (mass/mass) m/s Reflectance factor % Reflection (optical) density Resistance to water penetration Resistance to grease penetration Ring crush Roughness, Print-surf Roughness, Bendtsen Saleable mass Surface resistivity Smoothness, Bekk Static bending force J, kj numerical value min, h, d min, h, d kn/m μm ml/min kg Stock concentration % Stretch at break % Swelling after water immersion % Ohm s mn, N Tear index mnm 2 /g Tearing strength Tensile index N N m/g Tensile energy absorption J/m 2 Tensile stiffness N/m Tensile stiffness index Nm/kg Tensile stiffness orientation (degree with decimal (polar angle) sub-divisions) Tensile strength kn/m Tensile toughness index Jm/kg Tensile toughness J/m Thickness μm,mm Transmission (optical) density numerical value Volume resistivity Q m Water absorbency g/m 2 area basis g/m 2 mass basis % capillary rise mm Water vapour transmission rate g (m 2 d) z-direction strength properties kn/m 2 17

20 Xl Table of conversion factors Most of the world has accepted the International System of Units-Systeme International d Unités (SI) as the standard system for measurement. Test methods and standards require SI units as the primary reporting value. We trust that this guide will be useful when converting between different units (FPS foot-pound-seconds and SI units). FPS unit Faktor Sl-unit A acres m 2 B Btu (IT) kj Btu/h W Btu/(h ft of) W/(m K) Btu/(h.ft2. OF) W/(m 2 K) Btu/lb J/g Btu/(lb of) x 103 J/(kg K) F fl oz (Imp) cm 3 fl oz (US) cm 3 ft H20 (39,2 F) kpa ft m ft m 2 ft m 3 ft/min 5.08 mm/s ft/min m/s ft 3 /min m 3 /h ft/s m/s ft 3 /s l/s ft lbf J ft lbf/in kj/m 2 ft lbf/ft J/m 2 ft lbf/s W G gal(us) I gal(lmp) I gal(us)/d m 3 /d gal(us)/min I/min gal(lmp)/min x 10-5 m 3 /s gal(us)/min x 10-5 m 3 /s grains/yd g/m2 H hp (550 ft-lbf/s) kw hp h MJ I in 25.4 mm in cm 2 in cm 3 inhg (32 F) kpa inhg (60 F) kpa inh20 (60 F) kpa in lbf N m in lbf J in lbf/in J/m 2 in ozf mj FPS unit Faktor SI-unit K Kgf/in kn/m L Ib kg Ibf mn Ibf N Ibf in Nm Ibf/in kpa Ibf/in N/m Ibf/in kn/m Ibf/in kn/m 2 Ibf/in kpa Ibf ft N m Ibf/ft Pa Ibf/15 mm kn/m Ibf s/ft Pa s Ibf/ft kg/m 3 Ib/1000 ft g/m 2 Ib/3000 ft g/m 2 Ib/in Mg/m 3 Ib/gal (US) kg/l Ib/ream, 17 x g/m 2 Ib/ream, 24 x g/m 2 Ib/ream, 25 x g/m 2 M mi km mi km 2 mil (0,001 in) 25.4 IJm mil (0,001 in) mm O oz (avoir.) g oz (US fluid) ml ozf N ozf/in N/m oz/gal (US) g/l P psi kpa T ton (short) tonnes(t) ton (short)/l 00 ft t/m 2 y yd m yd m 2 yd m 3 yd 3 /s m 3 /s 18

21 Paper Standards & Measurements is one in a series of Sappi s technical brochures. Through them, we share our paper knowledge with our customers so that they can be the best they can be. PROCESSING MATT PAPERS ON-PRESS TROUBLESHOOTING FOLDING AND CREASING CLIMATE AND PAPER MOTTLING- MOTTLED IMPRESSION THE PAPER MAKING PROCESS PAPER, INK AND PRESS CHEMISTRY ADHESIVE TECHNIQUES THE PRINTING PROCESS For comprehensive technical information sappi The word for fine paper

22 Cover HannoArt Gloss 250 g/m 2, Text HannoArt Gloss 150 g/m 2, 2007 Sappi Europe SA Sappi Fine Paper Europe Sappi Europe SA 154 Chausseé de la Hulpe B-1170 Brussels Tel (0) Fax + 32 (0) sappi The word for fine paper