1、T 832 om-12 OFFICIAL METHOD 1994 REVISED 1998 REVISED 2003 REVISED 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 connection with th
2、e 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 Method TAPPI CA
3、UTION: 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 precautions are c
4、omplete 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 the handling o
5、f 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 whether any of
6、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. Water absorption of corrugating medium: float curl meth
7、od 1. Scope and summary 1.1 The water absorptivity of corrugating medium is measured by floating a specimen on the surface of a vessel of water and determining the time for the specimen to become saturated. 1.2 This method is applicable to corrugating medium as it is commercially produced by all pro
8、cesses. It is generally applicable to relatively unsized (water leaf) paperboards. It may not be applicable for more highly sized boards or to grades produced in different grammage (basis weight) from those normally used in corrugating medium. 1.3 TAPPI T 432 “Water Absorbency of Bibulous Papers” an
9、d TAPPI UM 596 “Water Absorbency of Non-Bibulous Paperboard” have been used to measure the water absorptivity of corrugating medium, but the study which led up to the development of this method indicates that they lack the repeatability of this method and most certainly take more time to conduct, es
10、pecially on the more resistant samples. 2. Significance The absorptivity of corrugating medium must be controlled to some extent in order that it has the proper receptivity to the corrugating adhesive, which is an aqueous suspension of starch, for proper adhesion in the corrugating process. A test f
11、or absorptivity is necessary for control. The absorptivity may relate to the way the medium can be steamed by the showers on the singlefacer and by the preconditioner. 3. Apparatus and materials 3.1 Open dish or vessel, to contain the water and float the specimen. A 145 cm3(8.85 in3) or larger evapo
12、rating dish has been found satisfactory, but any similarly sized vessel is adequate. 3.2 Distilled water or deionized water, pH 6.5 to 7.5, 23.0 1.0C (73.4 1.8F). 3.3 Stopwatch or timer. T 832 om-12 Water absorption of corrugating / 2 medium: float curl method 4. Sampling and test specimens 4.1 Sele
13、ct sample according to TAPPI T 400 “Sampling and Accepting a Single Lot of Paper, Paperboard, Containerboard, or Related Product.” 4.2 Condition according to TAPPI T 402 “Standard Conditioning and Testing Atmospheres for Paper, Board, Pulp Handsheets, and Related Products.” Conduct test in atmospher
14、e corresponding to TAPPI T 402. 4.3 From each test unit of the sample, select at least ten specimens, and cut each of them to approximately 50 50 mm (2 2 in.). Alternatively, cut ten such specimens from a single composite test unit. 4.4 Determine the felt (top) and wire (bottom) side (T 455) of each
15、 specimen. Make a small mark identifying the wire (bottom) side. 5. Procedure 5.1 Gently place the test specimen, top or felt side down, on the surface of the distilled water in the vessel or dish and, at the same instant, start the stopwatch or timer. 5.2 The specimen will first curl upward due to
16、the absorption of water by the surface in contact with the water. Then as it becomes saturated, the strains will be equalized, the stiffness is relaxed, and the specimen will flatten out again to almost its original shape. 5.3 Record the time in seconds required for the specimen to curl upward and r
17、eturn to its flat position on the surface of the water. NOTE 1: When making this water absorptivity test, check the pH of the water periodically to assure it does not drift outside the acceptable range. Varying pH can have an affect on the test results. 6. Report For each test unit, report as the te
18、st result the average total elapsed time for ten test specimens. Also report the elapsed time for each test specimen. 7. Precision 7.1 The precision of this method was determined by a round-robin evaluation (1991) of this and several other methods by eight laboratories on samples of corrugating medi
19、um from eight different mills made by a variety of processes with a wide range of absorptivity levels. Tests were made both before and after aging. 7.2 The following estimates of precision are based on these results: 7.2.1 Repeatability = 12% of average according to definitions of TAPPI T 1200 “Inte
20、rlaboratory Evaluation of Test Methods to Determine TAPPI Repeatability and Reproducibility.” 7.2.2 Reproducibility = 61% of average, computed from the Coefficient of Variation, as described in TAPPI T 1200. 8. Keywords Corrugating medium, Absorptivity, Water absorption, Float curl method, Adhesion
21、9. Additional information 9.1 Effective date of issue: April 24, 2012. 9.2 Two alternate methods may be performed in the same general time period with roughly similar repeatability are also described below. They do not give the same numerical results, but, in general, will rank the materials in the
22、same order as the preferred method. 9.2.1 An alternate procedure which is particularly useful in a corrugating plant for measuring the water absorptivity of corrugating medium as it is being used is TAPPI T 831 “Water Absorption of Corrugating Medium: Water Drop Penetration Test.” 9.2.2 Another alte
23、rnate procedure, for measuring the water absorptivity of corrugating medium is TAPPI T 835 “Water Absorption of Corrugating Medium: Water Drop Absorption Test.” 9.3 Wet curl is one factor that can affect starch bonding. However, it is not the only factor as even sized liner when used as medium can b
24、ond. Therefore, this test is useful as a control test, but one has to be careful in assessing 3 / Water absorption of corrugating T 832 om-12 medium: float curl method medium on a go no-go basis using this test alone. 9.4 The absorptivity of corrugating medium has been known to change markedly, typi
25、cally decreasing (an increase in penetration time) with aging. Usually this change will be greatest during the first day or days after manufacture. Therefore, to compensate for those expected changes, many mills induce artificial aging as part of their off-machine control testing of absorptivity. Us
26、ually some form of elevated temperature constitutes the artificial aging process. There is no established protocol for times and temperatures for artificial aging, and different labs have different procedures to simulate the aging process. 9.4.1 Some possible conditions are: , 2, or 7 h at 105C (221
27、F); 15 min at 190C (374F) (this is designed strictly for an off-machine test at the time of manufacture). One laboratory found that 2-8 h at 105C (221F) gave aging equivalent to one month under natural conditions. 9.4.2 There is good indication that the aging effect is due to oxidation. One laborato
28、ry reported that samples from the outside layers of a roll had increased in absorption time 25-fold, while the inner layers were unchanged in a 10-month storage. 9.4.3 One laboratory found a close relationship of aging with the amount of alcohol benzene extractives in the medium. If these materials
29、are as described in TAPPI T 204 “Solvent Extractives of Wood and Pulp,” aging could indeed be an oxidation, a chemical reaction. Using the general rule of thumb for acceleration of a chemical reaction, the aging time could be halved by increasing the temperature by 10C (50F). 9.5 In the 2012 revision, the appendix on artificial aging was consolidated and moved into the additional information section and various minor textural corrections were made. Your comments and suggestions on this procedure are earnestly requested and should be sent to the TAPPI Standards Department. g
