1、TAPPI/ANSI T 555 om-15 PROVISIONAL METHOD 1994 OFFICIAL METHOD 1999 REVISED 2004 CORRECTION 2005 REVISED 2010 REAFFIRMED 2015 2015 TAPPI The information and data contained in this document were prepared by a technical committee of the Association. The committee and the Association assume no liabilit
2、y or responsibility in connection with the use of such information or data, including but not limited to any liability under patent, copyright, or trade secret laws. The user is responsible for determining that this document is the most recent edition published. Approved by the Standard Specific Int
3、erest Group for this Test Method TAPPI CAUTION: This Test Method may include safety precautions which are believed to be appropriate at the time of publication of the method. The intent of these is to alert the user of the method to safety issues related to such use. The user is responsible for dete
4、rmining that the safety precautions are complete and are appropriate to their use of the method, and for ensuring that suitable safety practices have not changed since publication of the method. This method may require the use, disposal, or both, of chemicals which may present serious health hazards
5、 to humans. Procedures for the handling of such substances are set forth on Material Safety Data Sheets which must be developed by all manufacturers and importers of potentially hazardous chemicals and maintained by all distributors of potentially hazardous chemicals. Prior to the use of this method
6、, the user must determine whether any of the chemicals to be used or disposed of are potentially hazardous and, if so, must follow strictly the procedures specified by both the manufacturer, as well as local, state, and federal authorities for safe use and disposal of these chemicals. Roughness of p
7、aper and paperboard (Print-surf method) 1. Scope This method measures the roughness of paper and paperboard under conditions intended to simulate the nip pressures and backing substrates found in printing processes. It is applicable to coated and uncoated papers and paperboards which are intended to
8、 be printed by contacting printing processes. The measuring principle, that of determining the resistance to flow or air between the test surface and a metal band in contact with it, is similar to that employed in TAPPI Test Method T 538 om-96 “Roughness of Paper and Paperboard (Sheffield Method).”
9、The major difference between this and other air leak methods is that the metal band dimensions, clamp pressures and composition of the measuring nip are all intended to simulate printing process conditions. 2. Summary The measuring head, which carries a circular metal measuring land surrounded by co
10、ncentric guard lands is pressed against the specimen, which is supported by a resilient backing surface consisting of lithographic blanket or other material designed to simulate backing materials used in printing processes. Air under pressure is led into the gap between one of the guard lands and th
11、e measuring land and the rate of flow between the edge of the measuring land and the specimen is measured. 3. Significance Surface roughness is a significant factor in determining the printability of papers and paperboards. By measuring roughness under conditions approximating letterpress, litho and
12、 gravure printing processes this method yields information relevant to the performance of the product during printing. The results of the test are expressed directly as an average value of roughness in micrometers, which in many cases correlates better with printability than other comparable T 555 o
13、m-15 Roughness of paper and paperboard (Print-surf method) / 2 methods. In some cases, it is possible to relate average roughness to ink film thickness, thus providing guidance on setting printing conditions. 4. Definition 4.1 Print-surf roughness. The mean gap between a sheet of paper or board and
14、a flat circular land pressed against it under specified conditions. The mean gap is expressed as the cube root mean cube gap calculated as prescribed in Appendix A.1 4.2 Print-surf compressibility, K. The percentage decrease in surface roughness when measurements are made consecutively at two of the
15、 standard clamping pressures specified in this method. The surface compressibility, K, can be defied mathematically by the equation: K = 100 (G1 G2)/G1Where G1and G2are the surface roughness values obtained at the two clamping pressures, with G1being the lower pressure. 5. Apparatus 5.1 Air supply.
16、A source of clean air, free of oil and water droplets, at a steady pressure within the range 300 kPa (43 lb/in.2) to 600 kPa (86 lb/in.2). If the instrument is not provided with internal air filters the provision of an external oil mist filter having an effective screening efficiency of 99.99% at 0.
17、5 mm particle size is recommended. Fig. 1: The sensing head sectioned on two radii. 5.2 Sensing head. A circular head of the form shown in Figs. 1 and 2, consisting of steel lands, which have coplanar, polished surfaces. The center or measuring land shall be 51.0 m 1.5 m wide and have an effective l
18、ength of 98.0 0.5 mm. The two guard lands shall each be at least 1000 m wide at any point and the radial distance between them at any point shall be 152 m 10 m. The measuring land shall be centered between them to within 10 m. The lands shall be fixed in an airtight mounting constructed so that air
19、can be passed into the gap between the inner guard land and the measuring land and exhausted from the gap between the measuring land and the outer guard land. A spring loaded protective collar may be fitted outside the guard lands. The measuring head should be readily detachable for cleaning and so
20、should be constructed in such a way that an airtight seal between the head and the air inlet and outlet ports may be easily formed and maintained. In most commercially available instruments the back of the head is ground and lapped to mate with an air manifold. 3 / Roughness of paper and paperboard
21、(Print-surf method) T 555 om-15 Fig. 2: Plan of the measuring and guard lands of the sensing head. 5.3 Sensing head air pressure regulator. The sensing head shall be supplied with air regulated at a known differential pressure. In instruments employing variable area flowmeters and following the orig
22、inal Parker design the differential pressure across the measuring land and flowmeters is specified as 6.2 0.1 kPa or 19.6 0.1 kPa. Later instruments employing electronic flow measurement techniques may require different differential pressure settings and tolerances. 5.4 Resilient backings. Two types
23、 of resilient backings are normally available for use in pressing the test piece against the sensing head. The backings are in the form of disks, at least 10 m greater in diameter than the outside diameter of the guard land. 5.4.1 Soft backing. Consisting of a rubber offset printing blanket composed
24、 of a layer of synthetic rubber at least 600 m thick, bonded to a fabric backing giving an overall thickness of at least 2000 m 200 m. The apparent hardness of the complete backing is 83 6 IRHD (international rubber hardness degrees). 5.4.2 Hard backing. A composite consisting of a layer of polyeste
25、r film bonded at its periphery to cork, offset blanket or similar material. There is a small exhaust hole in the center of the polyester disk to prevent the entrapment of air between the disk and the cork. The apparent hardness of the assembly is 95 2 IRHD. 5.5 Backing holders. Rigid disks, each rec
26、essed to accommodate a resilient backing disk. The design and construction of the holder must be such that the applied clamping pressure is transmitted to the test piece. NOTE 1: It has been observed that high stiffness papers and boards can react negatively with the flat metal backing holder and ca
27、use erroneously high roughness results. This problem can be solved by using a modified backing holder which relieves those areas of the backing holder not directly below the measuring land, as shown in Fig. 3. Fig. 3. Modified backing holder. The resilient backing should be secured to the holder by
28、a suitable means, e.g. double-sided adhesive tape. 5.6 Clamping mechanism, allowing clamping of the test piece between the backing and the sensing head during the measurement cycle. The clamping system should allow the selection of either of the following three clamping pressures; 490 30 kPa, 980 30
29、 kPa or 1960 30 kPa. T 555 om-10 Roughness of paper and paperboard (Print-surf method) / 4 NOTE 2: Some users of this instrument prefer to use clamping pressures displayed in units of kgf/cm2, i.e. 5, 10 and 20 kgf/cm2. The clamping pressure is calculated from the total area of the measuring and gua
30、rd lands. The construction of the clamping mechanism should be such that, when activated, the system reaches 90% of its final value in approximately 0.4 s and 99% of its final value in approximately 0.8 s. 5.7 Measuring system. Any measuring system may be employed which is able to measure the flow o
31、f air between the measuring land and the clamped test piece, convert it to the “cube root mean cube gap” in accordance with Appendix A.l and display the roughness value in micrometers. Examples of measuring systems which have been successfully employed in commercial instruments include: 5.7.1 Variab
32、le area flowmeter instruments. Air leaking between the measuring land and the test piece is collected and passed through a variable area flowmeter calibrated to read directly in micrometers roughness. The range of such instruments is normally 0.6-6.0 micrometers and a number of variable area flowmet
33、ers, usually four, may be necessary to cover the range. In the one known commercial instrument of this type the flowmeters are calibrated at a differential pressure of 6.2 0.1 kPa and the pressure across the sensing head must be maintained at this value throughout the test by the measuring air regul
34、ator. 5.7.2 Impedance type instruments. The design and construction of the Print-surf measuring head is such that the relationship between differential pressure and airflow, after correcting for compressibility of air, is substantially linear below some limiting value of differential pressure. It is
35、 therefore possible to calculate the airflow through the head by comparing the pressure drop across the head with that across a known fluidic impedance connected in series with it. The differential pressures can be readily measured with suitable transducers and the value of the reference internal fl
36、uidic impedance determined during manufacture. The roughness of the test piece may be calculated from the transducer outputs and the impedance value. One advantage of this type of measuring system is that it is largely independent of measuring air pressure below a certain limiting value. The measuri
37、ng system shall make the measurements necessary to calculate roughness of the test piece 4.5 0.5 s after the application of the clamping force. 6. Calibration 6.1 Wherever possible calibration traceable back to national or international standards should be employed. Calibration should be carried out
38、 before commissioning the instrument and at regular intervals dependent on the use of the instrument and the manufacturers recommendations. 6.2 The calibration of electronic type Print-surf instruments using methods traceable to national standards is considered to be outside the capability of most p
39、aper testing laboratories. A description of possible procedures is given in ISO 8791-4, Annexes D and E (including restrictor heads. paper standards and plastic discs). It should be emphasized that cooperation of the manufacturer of the instrument may be required for such calibrations to be accompli
40、shed. 6.3 Clamping system. Clamp pressures may be checked by connecting a calibrated pressure gauge or pressure transducer system into the pneumatic clamping circuit. It is necessary to make allowance for the mass of the clamp platen, backing and holder, and the resistance of the spring loaded prote
41、ctive collar when calculating the effective clamp pressure. 6.3.1 A second, preferred method, is to interpose a calibrated load cell between the backing and the measuring head. If this is done it is essential to position the measuring surface of the load cell in the plane normally occupied by the te
42、st piece, and special fittings may be required to accomplish this. 6.3.2 The rate of application of clamping force may be determined by connecting a high speed recording device such as a storage oscilloscope to the output of the pressure transducer or force gauge used to verify clamp pressure. 6.4 M
43、easuring system. 6.4.1 Variable area flowmeter instruments. These may be calibrated by means of a soap film flowmeter. A suitable procedure is given in Appendix A.2. 6.4.2 Instruments employing flow or pressure transducers. The dynamics of the measuring process and the critical nature of the airway
44、shapes and volumes make it impractical to calibrate the system pressure transducers by connecting an external pressure gauge in parallel. The value of the internal fluidic impedance may not be verified without partial disassembly of the instrument. Because of these difficulties manufacturers of Prin
45、t-surf type instruments make available ISO reference standards of level 3 which may be used to calibrate the complete measurement system. These take the form of dummy sensing heads with known impedance values expressed in terms of roughness in microns. The use of these devices is detailed in Appendi
46、x A.3. 6.5 Sensing head. The dimensions of the measuring and guard lands may be verified by means of a Vernier microscope or other suitable device. The profile and surface finish of the measuring land is critical but may only be 5 / Roughness of paper and paperboard (Print-surf method) T 555 om-15 c
47、hecked by comparison with reference sensing heads held by manufacturers or ISO Authorized Laboratories. Comparisons may be made by the exchange of paper samples or specially manufactured plastic disks which are available with a range of replicated rough surfaces. 6.6 Backing disks. The apparent hard
48、ness of the backing disks, after mounting in the holder, may be measured using a suitable hardness tester. 7. Sampling Sample the paper or paperboard in accordance with TAPPI T 400 “Sampling and Accepting a Single Lot of Paper, Paperboard, Containerboard or Related Product.” 8. Conditioning Conditio
49、n the sample in accordance with TAPPI T 402 “Standard Conditioning and Testing Atmospheres for Paper, Board, Pulp Handsheets and Related Products.” 9. Test specimens 9.l Prepare the test specimens in the same atmospheric conditions used to condition the sample. Cut at least 10 test specimens for each side to be tested. The minimum size for each test specimen shall be 100 mm x 100 mm and the surfaces shall be identified in some convenient way. 9.2 The test area shall be free of all folds, wrinkles, holes and other defects and
