Abstract:

Objective The dry indoor environment causes non-negligible impact on human health. The permeable evaporative humidifier with humidifying core as liquid guiding tunnel showed some positive effect on the indoor humidity management. This paper reports research on a type of humidifier material made following the bionic bamboo structure, and discusses the influence of the design of this material on the sample water conduction and fast drying performance, aiming for improvement of environmental protection by presenting an efficient humidifier inner core.

Method In this study, PLA micro-nano fiber fabric was prepared by hydrophilic modification of PLA with sodium secondary alkyl sulfonate (SAS) as the main raw material. Viscose fiber was prepared into viscose fiber layer (CEL) by carding process, and the hot-rolled PLA/CEL nonwoven composite was wound to obtain the fiber wiener humidification material. The samples were characterized by Fourier infrared spectrometer(FT-IR) and scanning electron microscope. In addition, liquid contact angle measuring instrument, drying rate tester, electronic fabric strength tester and self-built instrument were used to study the water conduction fast drying characteristics and physical and mechanical properties of the samples.

Results In terms of micro-morphology, the biomimetic bamboo-tube fibrous humidification material has a continuous or quasi-continuous layered micropore distribution structure parallel to the length direction, providing power for the directional transmission of liquid, wherein the biomimetic bamboo-tube fibrous laminated structure is loose inside and tight outside to provide the basis for the high-speed transmission of liquid. The increase of wind pressure reduced the fiber diameter distribution and pore size distribution in the sample, leading to a high-quality porous structure for efficient liquid transport. FT-IR test showed that the infrared spectra of C—O—C vibration absorption (1 181 cm^-1) and C—O tensile (1 081 cm^-1) peaks were enhanced after SAS addition, and the liquid contact angle of the sample surface was significantly changed, indicating that SAS successfully improved the hydrophilicity of PLA micro-nano fiber fabric. On the other hand, appropriate changes of melt blowing air pressure and sample density change had a certain optimization effect on the water conduction and quick drying characteristics of the fibrous humidifying materials. The experimental results showed that when the melt-blowing air pressure was 36 kPa and the simple density was 1.1 g/cm³, the liquid absorption rate and drying rate of the sample were the best, which were 112.4 mg/s and 1.03 mL/h, respectively. Compared with the sample density of 1.8 g/cm³, the liquid absorption rate and drying rate are increased by 55.2% and 51.5%. At this time, the tensile breaking strength of the sample reached 255.2 N, and the breaking strength decreased by 10.8% compared with that of the crimp density of 1.8 g/cm³. When the air pressure increased from 24 kPa to 40 kPa, the liquid absorption rate increased from 80.1 mg/s to 108.4 mg/s, representing a 26.1% increases. Drying rate increased by 21.1% from 0.57 mL/h to 0.69 mL/h, and the tensile breaking strength increased by 32.1% from 262.2 N to 346.4 N. The bionic bamboo structure is conductive to the improvement of the water conduction and fast drying performance of the fiber wiener humidification material, which can meet the application requirements of the humidifier.

Conclusion The humidifying material with biomimetic bamboo-tube joint structure prepared by lamination design has a wide development prospect in the field of water conduction and rapid drying. Among them, polylactic acid, as a bio-based material, has excellent antibacterial and mildew resistance properties, which is in line with the concept of green environmental protection development. Moreover, by changing the porous structure and lamination process of the fiber humidifier material, the water-conducting and quick-drying ability of the sample is further regulated, which provides references and examples for the structural design and green preparation of the high-performance fiber humidifier core.

Key words: polylactic acid, melt blowing, nonwoven, biomimetic bamboo-tube, water quickly dry, humidifying core, viscose fiber