Experimental data of water swelling characteristics of polymer materials for tunnel sealing gasket

This article provides comprehensive experimental data of two polymers for shield tunnel sealing gasket: i) water swelling polyurethane (WSP) and ii) a mixture (WSRP) of WSP and water swelling rubber (WSR). Water-swelling tests are conducted to investigate the microstructural changes and properties of both WSP and WSRP during water swelling. These data can be useful for the quantitative evaluation of water swelling performance of WSP and WSRP. The data presented herein was used for the article, titled “Experimental investigation of water swelling characteristics of polymer materials for tunnel sealing gasket” [1].


Value of the data
• Material and Engineering • The comprehensive data can be used for the quantitative evaluation of water swelling performance of WSP and WSRP considering the pH, solution concentration, and loading pressure • The data of water swelling tests are valuable for better understanding the swelling mechanism of WSP and WSRP • The data provides reference for material selection of WSR and WSP

Data description
The data consists of swelling tests which is altered to evaluate swelling capacity of WSP and WSRP. Specially, the samples were divided into blocks with dimensions of 20 mm × 20 mm × 2 mm [1] . The initial weight of a sample was recorded ( W 0 ), and then the sample was immersed in the soaking solution. After a period, the sample was removed and reweighed ( Wt ) after removing the surface water by blotting with a tissue paper until a stable value was reached. The swelling ratio already defined in the research publication [1] as following equation.
where S w is the water-swelling ratio of the sample, W 0 is the initial weight of the sample, and W t is the weight of the sample after soaking for a certain period. Because each measurement was done in triplicate, three experimental results for each condition were shown in the following tables. Tables 1 and 2 present the swelling ratio of specimens in distilled water and artificial seawater under different pH (Ph = 2, 4, 7, 10, and 12). Table 3 shows the swelling ratio of specimens under different solution concentration (distilled water, 20 g/L, 36 g/L, 40 g/L, and 60 g/L). Tables 4 , 5 and 6 present the swelling ratio of specimens under different loading pressure (100 kPa, 170 kPa, and 240 kPa) for WSP, WSRP1 and WSRP 2, respectively.

Design, materials and methods
The water swelling polyurethane (WSP) and water swelling rubber (WSR) are two polymer materials that provide water resistance by swelling when they are soaked in water [1 -4] under leaking situation [5 -8] . The WSP material was prepared first by adding TDI, and prepolymer. Then, WSRP was obtained by adding sodium polyacrylate, prepolymer, and WSR. Detailed preparation procedure can be found in Wang et al. [1] .
In this study, the effects of pH, solution concentration, and loading pressure on waterswelling capacity of WSP and WSRP (1 and 2) are investigated. The soaking solutions contain distilled water and artificial seawater according to Marcet's principle [1] .  Table 4 The swelling ratio of WSP with swelling time under different loading pressure conditions.  Table 5 The swelling ratio of WSRP 1 with swelling time under different loading pressure conditions.

Measurement data
In this data article, the swelling ratio is altered to characterize the swelling capacity of WSP and WSRP (1 and 2). Table 1 shows the swelling ratio of WSP (or WSRP) in distilled water with swelling time under different pH conditions. Table 2 shows the swelling ratio of WSP (or WSRP) in artificial seawater with swelling time under different pH conditions. Table 3 shows the swelling ratio of WSP (or WSRP) with swelling time under different solution concentration conditions. Table 4 shows the swelling ratio of WSP with swelling time under different loading pressure conditions. Table 5 shows the swelling ratio of WSRP 1 with swelling time under different loading pressure conditions. Table 6 shows the swelling ratio of WSRP 1 with swelling time under different loading pressure conditions.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.