1、T 547 om-12 PROVISIONAL METHOD 1988 OFFICIAL METHOD 1997 REVISED 2002 REAFFIRMED 2007 REVISED 2012 2012 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 liability or responsibility in conn
2、ection 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 Interest Group for this Test M
3、ethod 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 determining that the safety pre
4、cautions 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 to humans. Procedures for
5、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, the user must determine w
6、hether 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. Air permeance of paper and paperboard (Sh
7、effield method) 1. Scope 1.1 This method is used to measure the air permeance of a circular area of paper using a pressure differential of approximately 10 kPa (1.5 psig). In order to accommodate a wide range of paper products, rubber clamping plates are available for five commonly used orifice diam
8、eters: 9.5 mm (0.375 in.), 19.1 mm (0.75 in.), 38.1 mm (1.50 in.), 57.2 mm (2.25 in.), and 76.2 mm (3.00 in.). The air flow range for this method is 0 to 3348 mL/min (0 to 400 Sheffield units). Instruments are available with either variable area flowmeters (glass tubes with internal tapers and float
9、s) or electronic mass flowmeters. 1.2 This method measures the air that passes through the test specimen, along with any possible leakage of air across the surface; therefore it is unsuitable for papers with rough surfaces which cannot be securely clamped so as to avoid significant surface leakage.
10、1.3 For other methods of measuring the air resistance of paper using a 28.6 mm (1.125 in.) orifice diameter, refer to TAPPI T 460 “Air Resistance of Paper (Gurley Method)” or a test that operates at a pressure differential of 1.22 kPa, or TAPPI T 536 “Resistance of Paper to Passage of Air (High Pres
11、sure Method)” for 3 kPa. 2. Summary This method measures the rate of air flow that is directed to the rubber clamping rings that hold the test specimen. Compressed air, regulated at a fixed pressure, passes through a flow measuring device just before it is directed to the paper specimen test area, w
12、hich is defined by the diameter of the orifice in the rubber clamping rings. Air that passes through the paper specimen escapes to the atmosphere through holes in the downstream clamping plate. 3. Significance The air permeance of paper may be used as an indirect indicator of variables such as: degr
13、ee of beating, absorbency (penetration of oil, water, etc.), apparent specific gravity, and filtering efficiency for liquids or gases. Air T 547 om-12 Air permeance of paper and paperboard (Sheffield method) / 2 permeance is influenced by the internal structure and also surface finish. Internal stru
14、cture is controlled largely by the type and length of fibers, degree of hydration, orientation, and compaction of the fibers; as well as by the type and amount of fillers and sizing. The measurement of air permeance is a useful control test for machine production, but due to the number and complexit
15、y of factors outlined above, careful judgment should be used in the specification limits for air permeance. 4. Definition 4.1 Air permeance is the property of a sheet that allows the passage of air when a pressure difference exists across the boundaries of the specimen. It is quantified by measuring
16、 the rate of air flow through a specimen of given dimensions under specified experimental conditions. 4.2 Porosity is the ratio of pore volume to bulk volume. The porosity of paper is commonly evaluated by measuring its air permeance. 5. Apparatus15.1 The apparatus consists of a pressure controller
17、for the air supply, a pressure measuring device, an air flow measuring device, a test head (rubber ring clamping assembly) which clamps the specimen and establishes the test area, connecting tubing, and calibration restrictors. The air supply must be capable of supplying the necessary flow and press
18、ure to the system. It must be free of oil, water and other contaminants. The ideal condition for the air is to be equal to the temperature and humidity of the air in the conditioned laboratory environment. 5.1.1 A pressure controller to supply regulated air pressure to the system, upstream of the fl
19、owmeter. In the instruments that utilize variable area flowmeters with air bleeds for calibration, the pressure shall be regulated to 10.34 0.2 kPa (1.50 psig). In the instruments that utilize mass flowmeters with no air bleeds, the pressure shall be regulated to 9.85 0.2 kPa (1.43 psig), as this is
20、 the pressure measured downstream of the typical variable area flowmeters that have been calibrated by using air bleeds to atmosphere. 5.1.2 A pressure measuring device capable of measuring the regulated air pressure to the specified accuracy. 5.1.3 An air flowmeter having the capability to measure
21、the range of flow required for the samples to be tested. A range of 0 to 3348 mL/min, referenced to 1 atmosphere, 21C (0 to 400 Sheffield units) is recommended. The flow/pressure drop system response is defined in Equation 1: P = 9.86 - (0.4166 x 10-3) Q (1) where: P = specimen pressure differential
22、, kPa Q = airflow through the specimen (mL/min ref. 1 atmosphere, 21C) NOTE 1: Equation 1 for the system response was obtained from the traditional variable area flowmeter apparatus. This relationship is included here because systems that use electronic mass flowmeters must be “trimmed” to give a si
23、milar response, otherwise there will be significant differences in the test results (1). 5.1.4 A test head which securely clamps the specimen between pairs of rubber plates that limit the flow of air to the area of the specimen exposed by the orifice. Rubber clamping plates are available for the fiv
24、e commonly used orifice diameters: 9.5 mm (0.375 in.), 19.1 mm (0.75 in.), 38.1 mm (1.50 in.), 57.2 mm (2.25 in.), and 76.2 mm (3.00 in.). The pressurized side of the test head is located downstream from the flowmeter, and the air that discharges from the test specimen is free to exhaust to atmosphe
25、re. 5.1.5 Connecting tubing, of the proper length and diameter, as specified by the manufacturer. 5.1.6 Calibration restrictors, to be used as standards for checking or setting the calibration of the air flow measuring device. 1Names of suppliers of testing equipment and materials for this method ma
26、y be found on the Test Equipment Suppliers list, available as part of the CD or printed set of Standards, or on the TAPPI website general Standards page. 3 / Air permeance of paper and paperboard (Sheffield method) T 547 om-12 6. Calibration 6.1 The flow measuring device can be calibrated using elec
27、tronic mass flowmeters that have “NIST”-traceable calibration curves. The relationship between the traditional “Sheffield unit” and engineering units (mL/min) is shown in Table 1 (2). When using calibration restrictors, follow the manufacturers instructions. Table 1. Conversion of traditional Sheffi
28、eld units to engineering units Tube #3 Flow Tube #2 Flow Tube #1 Flow (SU) (mL/min) (SU) (mL/min) (SU) (mL/min) 0 0 50 313 160 1342 5 35 60 404 180 1509 10 70 70 495 200 1676 15 104 80 585 220 1843 20 139 90 676 240 2010 25 174 100 767 260 2178 30 209 110 858 280 2345 35 244 120 949 300 2512 40 278
29、130 1039 320 2679 45 313 140 1130 340 2846 50 348 150 1221 360 3014 55 383 160 1312 380 3181 60 418 170 1403 400 3348 180 1493 190 1584 Sheffield Recommended range Conversion to engineering Tube # Sheffield units (SU) units (mL/minute) 3 0 - 56 mL/min = 6.96 (SU) 2 56 - 170 mL/min = 9.08 (SU) - 141
30、1 170 - 400 mL/min = 8.36 (SU) + 4 mL/min = milliliters per minute referenced to 760 mm Hg and 21 C 6.2 Air pressure calibration can be performed with instruments traceable to the “NIST.” A pneumatic dead-weight tester is typically used. 7. Sampling To determine conformance to product specifications
31、, select a sample of paper in accordance with TAPPI T 400 “Sampling and Accepting a Single Lot of Paper, Paperboard, Containerboard, or Related Product.” 8. Test specimens Cut 10 test specimens from each test unit of the sample. A 125-mm (5-in.) square, or larger size is adequate. Each measured area
32、 should be free of thin or thick areas atypical of the sheet sample formation, and free of watermarks. 9. Conditioning Precondition, condition and test the specimens in an atmosphere in accordance with TAPPI T 402 “Standard Conditioning and Testing Atmospheres for Paper, Board, Pulp Handsheets, and
33、Related Products.” T 547 om-12 Air permeance of paper and paperboard (Sheffield method) / 4 10. Procedure 10.1 Calibrate the air flowmeter system in accordance with the manufacturers instructions. 10.2 Select the appropriate size rubber orifice plates. If using the type where various size inserts fi
34、t a master test head assembly, make sure that the gasket plate cavities and rubber plate surfaces are clean. Insert the upper and lower rubber orifice plates into the holders. 10.3 Insert the test specimen in the test head, between the rubber plates. Generally, if the smoother side of the specimen i
35、s facing downwards (towards the pressurized side), there will be less surface leakage. 10.4 Clamp the specimen between the rubber plates. Follow the manufacturers recommendation for the clamping pressure. Some test heads are pneumatically loaded, and some are mechanically loaded using a toggle-clamp
36、. 10.5 If using variable area flowmeter tubes, insert the plug that is connected to the flexible tubing (from the test head) into the quick coupling of the appropriate flowmeter tube. For other types of equipment, follow the manufacturers recommendations for connecting the test air. 10.6 Apply test
37、air pressure to the specimen after it is securely clamped. Some instruments are equipped with a toggle shut-off valve on the side of the test head base, while others have electrical controls. NOTE 2: It is desirable to clamp the specimen with no air flow passing through the orifice, as air flow can
38、cause the specimen to deflect. This may result in a creased sample, particularly when testing thin papers using the largest orifice size. 10.7 Record the flow measurement value after 4 1 second. 10.7.1 For instruments with variable area flowmeter tubes, the reading should be between the high and low
39、 calibration rings. Record the scale reading using the top of the float as soon as it is steady. If the reading is higher or lower than the calibration range, take a reading on the adjacent tube that would be in the proper range. If the reading is too high for the highest range flow tube, then selec
40、t a smaller orifice plate and return to step 10.2. If the reading is too low for the lowest range flow tube, then select a larger orifice plate and return to step 10.2. After testing the specimen, close the air shut-off valve and release the specimen. NOTE 3: To minimize errors, the largest possible
41、 orifice size should be used. Small orifice plates that keep the air flow readings below 30 Sheffield units may exhibit significant errors with only a small amount of air leakage in the instrument. 10.7.2 For instruments that use electronic air flowmeters with digital readout, follow the manufacture
42、rs recommendations. 10.8 Make a total of ten (10) readings, each on a separate test specimen (or an area of a larger sheet that has not been previously clamped). 10.9 When comparing several samples, maintain a consistent orifice size. In practice, it is possible to measure using different orifice si
43、zes and to normalize readings to one size. Refer to the formulas in Appendix A.2 for detailed air permeance calculations. 11. Report 11.1 Report the average of ten (10) readings in Sheffield Units, specifying the orifice diameter; or alternately in ISO Air Permeance Units (micrometer/Pascal-second).
44、 Also record the highest and lowest observed values, plus any values rejected in accordance with TAPPI T 1205 “Dealing with Suspect (Outlying) Test Determinations.” 11.2 Report the orifice diameter of the rubber plate used. 11.3 Report the flow tube number when using the variable area flowmeter type
45、 of instrument. 11.4 Report the identification of the specimen side placed downwards in the measuring head. 12. Precision 12.1 The following estimates of repeatability and reproducibility are based on data from the CTS-TAPPI Interlaboratory Program from 1997 through 2001. The materials on which thes
46、e data are based were various grades and weights of printing and writing papers. Only participants that were judged as acceptable by the interlaboratory analysis were included. The precision estimates are based on 10 determinations per test result and one test result per lab, per material. A more de
47、tailed chart of example results is included below. 12.2 Repeatability (within a laboratory) = 8.3%. 12.3 Reproducibility (between laboratories) = 17.5%. 12.4 Repeatability and reproducibility are estimates of the maximum difference (at 95%) which should be 5 / Air permeance of paper and paperboard (
48、Sheffield method) T 547 om-12 expected when comparing test results for materials similar to those described above under similar test conditions. These estimates may not be valid for different materials or testing conditions. Data Table of porosity results (Sheffield Units) Grand Mean Stnd Dev Betwee
49、n Labs Repeatability r and %r Reproducibility R and %R Labs Included 279 16 17 6.1% 44 15.9% 58 181 13 11 6.2% 35 19.4% 55 103 8 9 8.9% 22 21.2% 60 87.2 5.1 9.5 10.9% 14.1 16.2% 53 13. Additional Information 13.1 Effective date of issue: April 24, 2012. 13.2 Related methods: TAPPI Useful Method 524; ISO 5636-4. 13.3 The title of this method has been changed from “Air Permeability of Paper and Paperboard (Sheffield Method)” to “Air Permeance of Paper and Paperboard (Sheffield Method)” in order to better identify the property being tested. Air permeability is a
