Abstract:

Objective Conventional absorbent hygiene products (AHP) are primarily composed of polyolefin and polyester nonwovens as wrapping materials, exhibiting features such as high consumption rates, short usage cycles, challenging recyclability, and slow degradation. These attributes render them as significant contributors to fiber-based microplastic pollution. In contrast, cellulose-based nonwoven fabrics boast advantages like softness, permeability, and inherent biodegradability. The development of novel cellulose-based nonwoven materials presents a promising approach to mitigate the persistent microplastic pollution caused by non-degradable conventional absorbent hygiene products.

However, the wrapping layer of AHP must be hydrophobic to effectively contain fluid within the absorbent core and prevent rewetting against the skin. Therefore, the highly hydrophilic nature of cellulose nonwovens necessitates hydrophobic modification for this application.

Method The surface hydrophobic modification of bamboo pulp cellulose spunlace nonwoven fabric (BCNW) was conducted via a one-step urethanation reaction using 3-isocyanatopropyltrimethoxysilane (ISPTMOS) containing siloxane-based hydrophobic functional groups. Hydrophobicity, air-permeability, and mechanical properties of the modified nonwoven fabrics were investigated before and after modification. Furthermore, liquid penetration and anti-backflow properties of BCNW-ISPTMOS samples with different mesh sizes were quantitatively evaluated.

Results Compared to pristine bamboo pulp cellulose spunlace nonwoven fabric (B-BCNW), the modified fabric exhibited a transition from superhydrophilicity to hydrophobicity. The modified sample of BCNW-ISPTMOS demonstrated a water contact angle (WCA) of 135.5°, attributable to the blocking of hydrophilic hydroxyl groups in cellulose structure by low-surface-energy silane groups and enhanced surface roughness from silane cluster formation. Notably, the micro-scale silane clusters on the surface of the ultrasonically hydrolyzed hydrophobic bamboo pulp cellulose nonwovens (BCNW-ISPTMOS(U)) were converted into micro-nano scale, with partial nano-clusters encapsulated within silane layers. This structural evolution increased both hydrophobicity and hydrophobic stability, increasing the WCA to 139.2°. Concurrently, the reduced silane cluster size during ultrasonication decreased pore blockage in nonwoven matrix while improving fabric loftiness, resulting in enhanced air-permeability of 3 122 mm/s that meets permeability requirements for hygiene product surface layers. Furthermore, application performance tests revealed that when the mesh size was 2 mm, the hydrophobic mesh nonwoven exhibited good unidirectional liquid transport properties, with liquid penetration time, wet-back and run-off amount of 2.84 s, 0.012 g, and 1.403 g, respectively.

Conclusion Bamboo pulp cellulose nonwoven materials with integrated hydrophobicity and permeability were successfully developed through a one-step urethanation reaction between ISPTMOS and cellulose hydroxyl groups. The BCNW-ISPTMOS(U) demonstrated significantly enhanced hydrophobic performance, achieving a WCA of 139.2° with stable hydrophobic efficacy. Laser perforation experiments revealed that nonwoven with 2 mm triangular pore arrays optimally balanced liquid penetration and anti-backflow performance, confirming their potential as surface layer materials for absorbent hygiene products. However, current technological implementation faces dual constraints of high production costs and localized structural alterations due to laser processing. These limitations necessitate methodological innovations in research approaches to accelerate the industrial adoption of cellulose-based nonwovens in hygiene product manufacturing.

Key words: absorbent hygiene product, biodegradable material, hydrophobic modification, cellulose, unidirectional liquid transport, mesh, spunlace nonwoven