ANSI T 525 OM-2012 Diffuse brightness of paper paperboard and pulp (d 0) - ultraviolet level C.pdf

1、T 525 om-12 SUGGESTED METHOD 1972 HISTORICAL METHOD 1985 OFFICIAL TEST METHOD 1986 REVISED 1992 REVISED 2002 REVISED 2006 REVISED WITH TITLE CHANGE 2012 2012 TAPPI The information and data contained in this document were prepared by a technical committee of the Association. The committee and the Ass

2、ociation assume no liability 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 b

3、y the Standard Specific Interest 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 u

4、ser is responsible for determining 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 pre

5、sent serious health hazards 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. Prio

6、r to the use of this method, 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 thes

7、e chemicals. Diffuse brightness of paper, paperboard and pulp (d/0) ultraviolet level C 1. Scope 1.1 This method is for the determination of the brightness of white, near-white, and naturally colored pulp, paper, and paperboard. Brightness is a commonly used industry term for the numerical value of

8、the reflectance factor of a sample with respect to blue light of specific spectral and geometric characteristics. This method requires an instrument employing diffuse illumination and 0 viewing geometry 1.2 This method is applicable to all naturally-colored pulps, and papers and board made therefrom

9、. The measurement is not suitable for paper or paperboard containing added coloring matter (such as yellow or green dyestuff) which appreciably absorbs light in that part of the spectrum extending from about 400 to 500 nm. This brightness method is not applicable to colored papers. 1.3 Pulps to be t

10、ested shall be made into handsheets prepared according to TAPPI T 218 “Forming Handsheets for Reflectance Tests of Pulp (Bchner Funnel Procedure)” or T 272 “Forming Handsheets for Reflectance Tests of Pulp (Sheet Machine Procedure).” This method can also be used to measure the brightness of machine-

11、dried sheets. NOTE 1: The brightness of a handsheet will usually be 0.5 to 1.0 units higher than that of a machine-dried sheet made from the same pulp. 1.4 This method utilizes an integrating sphere to provide diffuse illumination and perpendicular (0) observation geometry (1) designated in optical

12、terminology as d/0. With this geometry, specimen surface structure and azimuthal orientation have a negligible effect on brightness. 1.5 The instrument has a relatively large specimen aperture for the purpose of averaging small area variations in reflectance, making it possible to obtain a reliable

13、average value with only a few individual measurements. 1.6 This method is not intended for use with colored materials. T 525 om-12 Diffuse brightness of paper, paperboard and pulp (d/0) / 2 2. Summary Diffuse reflectance is measured in the wavelength range of 400-520 nm with an effective wavelength

14、of 457 nm by using a suitable filter set or an equivalent device for modifying the spectral response and an instrument having diffuse illumination and perpendicular observation geometry. The measurements are made in terms of absolute reflectance factors. 3. Significance 3.1 Blue-light reflectance me

15、asurements were originally designed to provide an indication of the amount of bleaching that has taken place in the manufacture of pulp. The higher the blue-light reflectance, generally the whiter the products will appear. In recent years, the method has been extended to white and near-white paper a

16、nd paperboard, and is suitable for that purpose. The method provides a simple, single-number index useful for comparing similar white materials; however, colored materials are better identified by using a standardized three-dimensional color space see TAPPI T 524 “Color of Paper and Paperboard (45/0

17、 Geometry)” and T 527 “Color of Paper and Paperboard (d/0 Geometry)”. 3.2 Because the instrument geometry of this method is different from that of TAPPI T 452 “Brightness of Pulp, Paper and Paperboard (Directional Reflectance at 457 nm),” there is no simple relationship between the two brightness sc

18、ales (3). 3.3 Specularly reflected light (gloss) is excluded from the measurement of diffuse brightness by the use of a gloss trap (specular reflectance absorber) as required in 5.1.1.3. NOTE 2: Material containing fluorescent brightening agents will exhibit higher reflectance values to a degree whi

19、ch is dependent upon the ultraviolet (UV) content of the radiation incident on the specimen. Control of such UV content is essential to maintain continuity of measurement among optically brightened pulps. This method specifies that the level of UV excitation correspond to the equivalent level of CIE

20、 Illuminant C. NOTE 3: No known material is both perfectly reflecting and perfectly diffusing, but standards can be calibrated in terms of absolute reflectance factors (2,4). Standards with calibrations based on this reference can be obtained from Calibration Laboratories1, as defined in Section 5.3

21、 of TAPPI T 1211 “Acceptance Procedures for Calibration Laboratories.” 4. Definitions 4.1 Diffuse reflectance factor, the ratio of the radiance factor of a specimen to that of a perfectly reflecting diffuser, each being irradiated and viewed identically (4). 4.2 Absolute brightness, the diffuse refl

22、ectance factor for blue light in terms of a perfectly reflecting, perfectly diffusing specimen as determined on an instrument as described in Section 5. 4.3 Perfect reflecting diffuser, the ideal reflecting surface that neither absorbs nor transmits light, but reflects diffusely, with the radiance o

23、f the reflecting surface being the same for all reflecting angles, regardless of the angular distribution of the incident light. 5. Apparatus 5.1 Reflectometer1, an instrument designed for the measurement of diffuse reflectance which employs the following geometric, photometric, and spectral charact

24、eristics: 5.1.1 Geometric characteristics 5.1.1.1 One or more light sources direct light into an integrating sphere which provides diffuse illumination of the specimen. The integrating sphere has an inside diameter of 150 mm and is coated with a matte white paint with absolute reflectance of 96 or g

25、reater from the light source. The sphere shall be equipped with screens to eliminate direct illumination of the specimen. 5.1.1.2 The sum total of the areas of the apertures and other non-reflecting areas in the sphere does not exceed 13% of the area of the inner surface of the sphere. 5.1.1.3 The r

26、eceptor aperture is surrounded by a gloss trap (black circular area) of external diameter subtending a half-angle of 15.5 0.5 at the center of the specimen aperture. 1Names of suppliers of testing equipment and materials for this method may be found on the Test Equipment Suppliers list, available as

27、 part of the CD or printed set of Standards, or on the TAPPI website general Standards page. 3 / Diffuse brightness of paper, paperboard and pulp (d/0) T 525 om-12 5.1.1.4 No light reflected from the rim of the specimen aperture shall reach the receptor. 5.1.1.5 The measured test area on the specime

28、n is circular with a diameter of 28 mm 2 mm. 5.1.1.6 The specimen aperture diameter shall be 34 mm 1 mm and the edge thickness shall not exceed 1.5 mm. 5.1.1.7 The specimen is viewed perpendicularly (0). Only reflected rays within a solid cone, whose vertex is in the center of the specimen aperture

29、and of half-angle not greater than 4, shall fall on the receptor. 5.1.1.8 Stray light from all sources shall not exceed 0.5%. 5.1.2 Photometric characteristics. The accuracy of the photometer, whether mechanical or electronic, is such that the departure from photometric linearity after calibration d

30、oes not exceed 0.3% reflectance factor. 5.1.3 Spectral characteristics. The spectral distribution of the brightness function is shown in Table 1. This function has an effective wavelength of 457.0 nm 0.5 nm with a bandpass at half peak height of 44 nm. In a filter based reflectometer this spectral d

31、istribution is the product of the following variables: a) the relative spectral distribution of the reflectance of the integrating sphere, b) the spectral transmittance of the glass optics, c) the spectral transmittance of the filters, and d) the spectral response of the photoelectric cell(s). For a

32、 spectrophotometer or abridged spectrophotometer the spectral reflectance data obtained between 400 and 510 nm is to be integrated using the weighting function indicated in Table 1. Table 1. The relative spectral distribution function F() of a reflectometer equipment for measuring diffuse brightness

33、. Wavelength, nm F(), arbitrary units 5 nm weights Wavelength, nm F(), arbitrary units 5 nm weights 460 465 470 475 480 485 490 495 500 505 510 100.0 99.3 88.7 72.5 53.1 34.0 20.3 11.1 5.6 2.2 0.3 10.668 10.593 9.462 7.734 5.665 3.627 2.166 1.184 0.597 0.235 0.032 400 405 410 415 420 425 430 435 440

34、 445 450 455 1.0 2.9 6.7 12.1 18.2 25.8 34.5 44.9 57.6 70.0 82.5 94.1 0.107 0.309 0.715 1.291 1.942 2.752 3.680 4.790 6.145 7.467 8.801 10.038 Sum 937.4 100.000 Furthermore, the area under the curve of F() for wavelengths exceeding 700 nm should be small enough for the measurement not to be affected

35、 by any infrared fluorescent radiation generated in the sample. 5.1.4 Spectral radiance control: The instrument shall have some means of controlling the unltraviolet spectral radiance of the light entering the sphere and thus irradiating the sample (see Appendix A.1). 5.2 The following ancillary ite

36、ms must be available: 5.2.1 Reference standards, a non-fluorescent, white standard with a brightness calibration value with traceability to the perfect reflecting diffuser. If the instrument is to be calibrated for the measurement of fluorescent materials, a white fluorescent reference standard with

37、 traceability for CIE C standard illuminant conditions must be used. 5.2.2 Instrument standard(s), one or more opal glass or ceramic standards. 5.2.3 Black cavity, for calibration of the zero point of the photometric scale. This black body shall have a reflectance factor which does not differ from i

38、ts nominal value by more than 0.2% at all wavelengths. The nominal value is usually zero. 5.2.4 Lens tissue, non-fluorescent, non-abrasive lens paper or tissue. T 525 om-12 Diffuse brightness of paper, paperboard and pulp (d/0) / 4 6. Reagents Cleaning solution, distilled water and detergent free fr

39、om fluorescing or abrasive ingredients. 7. Calibration and standardization 7.1 Calibration Standards 7.1.1 Reference Standard, a non-fluorescent white standard with certified traceability to absolute reflectance. These must be obtained from Calibration Laboratories (see note 3). 7.1.2 Fluorescent Re

40、flectance Standard, a fluorescent reference standard with certified UV excitation traceability based upon CIE Illuminant C, to calibrate instruments for the measurement of fluorescent materials (see note 3). 7.1.3 Instrument Standard(s), one or more opal glass or ceramic instrument standards are req

41、uired. NOTE 4: A reference standard is used to transfer calibration from a Calibration Laboratory to a given instrument. Reference standards should never be cleaned as cleaning may change their value. Instrument standards should be used frequently to check the stability of a given instruments calibr

42、ation. An instrument standard evaluated on one instrument should never be used to calibrate another instrument. Instrument standards may be cleanable (consult the manufacturers instruction manual). 7.2 Calibration of instrument standard(s) 7.2.1 Procedure for instruments which are not equipped with

43、an internal instrument standard. 7.2.1.1 Turn instrument on and allow it to come to operating equilibrium. Consult instruction manual for manufacturers recommended warm-up time. 7.2.1.2 Clean one or more opal glass or ceramic instrument standards (per manufacturers instructions) if they have not bee

44、n cleaned recently. 7.2.1.3 Select the brightness measurement (457 nm) position. 7.2.1.4 Adjust the instrument to read the black cavity value with the black cavity in the specimen position. 7.2.1.5 Place the reference standard in the specimen position. Adjust the instrument to read the assigned valu

45、e. 7.2.1.6 Place an instrument standard in the specimen position and read and record the calibration value for this standard. Repeat this procedure to obtain values for additional standards if desired. 7.2.1.7 To calibrate for the measurement of fluorescent materials, use the fluorescent and non-flu

46、orescent reference standards per the manufacturers recommend procedure to achieve calibration for both standards. 7.2.2 Procedure for instruments equipped with an internal instrument standard. 7.2.2.1 Turn instrument on and allow it to come to operating equilibrium. Consult the instruction manual fo

47、r manufacturers recommended warm-up time. 7.2.2.2 Use the manufacturers recommended instruction to calibrate the instrument to the black cavity. 7.2.2.3 Place the reference standard in the specimen position. Use the manufacturers recommended procedure to establish calibration based on this standard

48、and to transfer calibration to the instruments internal instrument standard. 7.2.2.4 To calibrate for the measurement of fluorescent materials, the fluorescent and non-fluorescent reference standards must be used interactively per the manufacturers recommended procedure to achieve calibration for bo

49、th standards. NOTE 5: The reflectance of opal-glass or ceramic standards is relatively stable; however, they must be calibrated at regular intervals on the specific instrument with which they will be used by making use of reference standards and the procedures described in Section 7. 8. Use of instrument standards If instrument standards have been evaluated in accordance with the instructions in Section 7.2, one of the instrument standards may be used on a regular basis to check and, if necessary, reestablish calibration. If a second instrument