ACS Sustainable Chemistry & Engineering
pubs.acs.org/journal/ascecg
Research Article
Figure 6. Robustness investigation of the properties of EFB/(hairy) cellulose fiber nonwovens containing 10 wt % (hairy) cellulose fiber loading after remolding through the steam-rewetting approach: (A) tensile modulus; (B) tensile strength; (C) change in percentage points in filtration efficiency for PM 1 .
fibers as reflected in its R − 1 is governed by the stiffness of EFB fiber, which is the main fiber constituent that can resist deformation. 58,59 The presence of (hairy) cellulose fiber as a binder was crucial for stabilizing the deformed EFB fibers, particularly after drying. Wet filter cake consisting only 10 wt % unrefined cellulose fibers lacked sufficient strength to hold the EFB fibers in their deformed state, causing them to return to their original alignment and fail to achieve the intended curvature (Figure 5A). In contrast, the stronger wet filter cake formed by the hairy cellulose fibers as a binder effectively retained the deformed shape (Figure 5B), enabling the nonwoven EFB fibers to achieve and maintain the desired curvature. These results corroborate with the lower tensile properties of a hand sheet made from unrefined cellulose fibers compared to that made from refined cellulose fibers. 60 When molding an already-formed rigid EFB/(hairy) cellulose fiber nonwoven into a complex shape using the steam-rewetted approach, a similar trend was observed at 10 wt % (hairy) cellulose fiber loading where the deformation force increased significantly with refining time of the cellulose fiber used as the binder (see Figure 4F). The curvature of the nonwovens molded using this approach also followed a trend similar to that of the never-dried approach, with the EFB nonwoven using unrefined cellulose fiber as the binder showing a lower R − 1 of 0.076 mm − 1 , while those with hairy cellulose fibers as the binder consistently achieved 0.098 mm − 1 regardless of the refining time of the hairy cellulose fiber used. The moldability of nonwovens in the steam-rewetted approach is driven by the interaction between water from the steaming process and the (hairy) cellulose fibers as the binder. Water
placed over a metallic base with a circular hole surrounded by a curved edge with a radius of 10 mm (Figure 4C). A load was then applied (crosshead speed = 20 mm min − 1 ) to deform the wet material by 12 mm, followed by drying under the applied load at 120 ° C for 1 h to retain the deformed shape. The deformation of the materials was characterized by measuring the radius of the curved section (Figure 4D), labeled as R , which was then used to calculate the curvature (which is the inverse of R ). These results are summarized in Figure 4E for the never-dried approach and Figure 4F for the steam-rewetted approach. It is worth mentioning at this stage that both molding approaches did not work for the neat EFB fiber nonwoven without binder, as the loosely packed EFB fibers are held together only by friction, making the overall wet filter cake or steamed nonwoven structurally unstable. From Figure 4E, it can be seen that in the never-dried approach, the molding force increased with the increase of both the loading and refining time of the (hairy) cellulose fiber binder. The increase in the force required to mold with longer refining times can be attributed to the improved binding performance of the hairy cellulose fiber. The higher degree of fibrillation enhances the interaction and interlocking between the cellulose fiber binder and the EFB fibers, strengthening the wet web of the resulting nonwoven. 56 Additionally, the presence of fines within the wet web further improves frictional connections. 57 The curvature ( R − 1 ) of nonwovens molded using the never-dried state approach increased with increasing refining time of (hairy) cellulose fibers and approaches the target R − 1 of 0.01 mm − 1 (Figure 4E). The moldability of the wet filter cake of EFB/(hairy) cellulose
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https://doi.org/10.1021/acssuschemeng.5c00041 ACS Sustainable Chem. Eng. 2025, 13, 6209 − 6221
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