A Comparison of Three Durability Standards for Paper
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English Slovak |
| ISSN: | ISSN 0034-5806 |
| Online Access: | http://www.viks.sk/chk/res_3_95_161_174.doc |
| Abstract: | Conclusions. On the basis of these results concerning the three durability standards, the following conclusions can be drawn. All three durability standards demand about the same pH level. In practice, many papers do not meet these demands. Nevertheless, the pH demand seems to be reasonable. The same applies to the alkaline reserve. It is important that there be an alkaline reserve in the papers, so that the acid attack can be absorbed. All three standards demand a minimum of 0.4 mol/kg. A disadvantage of the DIN 6738 is that this standard expects that, if the papers meet the mechanical demands they automatically have the right pH and alkaline reserve. This is not the case, even in this research. With regard to the tearing resistance, NEN 2728 and ISO 9706 have reasonable demands, and they take the grammage of the paper in account. The demand of the DIN 6738 is low, and the effect of the grammage is not included. After accelerated aging, the decrease of the tearing resistance is small. NEN 2728 is the only one that includes the folding endurance. The initial minimum of double folds and the end result demand seem to be reasonable ones. With this test method the decrease after the accelerated aging can be followed well. The folding endurance has one disadvantage; the method has a quite large deviation in results. Concerning the tensile strength and the stretch at break, these are included in the DIN 6738. However, all the papers easily met the demands for these tests, as well before as after the accelerated aging; even the real nondurable papers. The disadvantages of the durability standards are listed below: NEN 2728 ˙ A large deviation in the folding endurance results. ˙ No classification possible. A paper is or is not permanent. ISO 9706 ˙ Only one mechanical test method is included. ˙ No accelerated ageing test is included. ˙ The minimum demand of the kappa number is too low. ˙ No classification possible. A paper is or is not permanent. DIN 6738 ˙ No formal demands for the pH and alkaline reserve. ˙ The minimum demands for the tearing resistance, tensile strength and stretch at break are quite low. ˙ The mechanical test methods are not suitable for determination of the decrease in strength after accelerated aging. ˙ Time-consuming to perform. The final conclusion is that NEN 2728 durability standard is the one that is the most related to the product paper. In this standard, the paper is submitted to both chemical and mechanical test methods as well as an accelerated aging test. As an extra test, it is recommended to include the measurement of the pH and alkaline reserve after the accelerated aging. Summaries. Three durability standards for paper are compared to determine their agreements and differences. The second objective was to find out what standard is most related to the product paper. In order to compare the durability standards NEN 2728, ISO 9706 and DIN 6738, five different paper grades were selected. These papers were all completely evaluated according to the durability standards. The major difference between the durability standards is that the ISO 9706 does not include an accelerated ageing test. All three standards have about the same demands for the pH and alkaline reserve. Only the DIN 6738 expects that, if the paper evaluated meets the demand for the mechanical test, it automatically has the right pH and alkaline reserve; this is not true. Concerning the mechanical analysis, all durability standards require that different tests be performed. From the results it was concluded that the NEN 2728 is the standard that is the most related to the product paper. In this standard paper is submitted to chemical and mechanical test methods and an accelerated aging test. |
|---|---|
| ISSN: | ISSN 0034-5806 |
