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EDITORIAL
Rethinking the Determination of Wet Strength of Paper Zicheng Chen, a,b Lanhe Zhang, a, * and Zhibin He b
The wet strength of paper is an important physical property, especially for household paper, e.g ., paper towels, as well as for some functional paper grades. However, in the literature, various conditions of immersing the samples in water before testing have been reported, resulting in differences in their extent of saturation and inconsistency in the testing results. Also, the dryness of paper specimens before the wet-strength testing is a critical parameter for the wet strength of paper; however, this aspect has been neglected in the literature. In this editorial, the methods of examination for both the temporary and permanent wet strength are discussed. A more reasonable method is proposed, such that the wet strength is reported according to the immersion time and the initial dryness of the paper. As an option, the results may be expressed as a function of immersion time and initial dryness. In this way, the trend of temporary wet strength related to the immersion time in water can be expressed clearly and the permanent wet strength also can be evaluated comprehensively.
.H\ZRUGV :HWVWUHQJWK 3DSHU 7HVWLQJ :DWHULPPHUVLRQWLPH 'U\QHVV &RQWDFWLQIRUPDWLRQ D 6FKRRORI&KHPLFDO(QJLQHHULQJ1RUWKHDVW(OHFWULF3RZHU8QLYHUVLW\-LOLQ-LOLQ 3URYLQFH35&KLQD E 'HSDUWPHQWRI&KHPLFDO(QJLQHHULQJ8QLYHUVLW\RI1HZ%UXQVZLFN )UHGHULFWRQ1%(%$&DQDGD &RUUHVSRQGLQJDXWKRU ]KDQJODQKH#FRP Wet Strength of Paper and Its Determination Method Thanks to the recyclable, green, sustainable, and cost-effective nature of paper, it has found applications in many fields, such as printing and writing, packaging, household use ( HJ ., towels), and some special applications. The strength properties of paper are key factors that determine how widely and how well paper is able to be used. The wet strength is very important for such paper products as kitchen towels, paper currency, and various specialty products, such as bags and filters. As its name suggests, the wet strength of paper is its strength after it gets wet. Likewise, the relative wet strength can be defined as the strength of the wet paper divided by the original strength when it was dry. The list of wet strength properties can be as long as the list of dry strength properties, LH tensile, tear, folding endurance, and so on. However, some of these wet strength properties are meaningless due to their low values. In TAPPI Method T456 om-3, which has been broadly adopted by global papermakers, the wet strength of paper is mainly defined as wet tensile strength. For paper grades with permanent wet strength, such as napkins and paper towels, applying a water immersion time longer than necessary to saturate the paper sample may not affect the test results of wet strength, as the wet strength of these paper grades are provided by crosslinking resin such as polyamide-epichlorohydrin (PAE), which is not affected by water. However, for some paper grades with temporary wet strength, such as facial tissue, the wet strength decays with increasing water immersion time. The specified temporary wet strength values of these paper products are usually achieved by addition of glyoxalated polyacrylamide (GPAM) chemistry, the effect of which lasts only seconds or minutes after moistening with
Chen et al. (2018 ). “ Rethinking determination wet strength ,” B io R esources 13(2), 2184-2186. 2184
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