Air Permeability Research Articles

Flexible Cellulose Nanofiber (CNF)-Nano- Montmorillonite (MMT) Composite Sheet Structure and Water Vapor Barrier Performance

One of the newly developed nanomaterials for functioning as high-performance packaging materials to replace synthetic plastics such as low-density and high-density polyethylene (LDPE, HDPE) is cellulose nanofiber (CNF). These substances are biodegradable, recyclable, and renewable. While cellulose nanofiber-based films have substantially better water vapor permeability than traditional packaging polymers, they have extremely low oxygen permeability. Water vapor permeability (WVP) of the spray-coated composites was decreased via spraying nano-montmorillonite (MMT) content into CNF suspension and also high-pressure homogenization of CNF-MMT suspension. The process for spraying cellulose nanofiber (CNF)-nano-montmorillonite (MMT) suspension on the stainless-steel surface was developed to produce a high-barrier performance composite. The two types of composites were prepared via spraying of raw CNF with MMT and fibrillated CNF with MMT via high-pressure homogenization. The structure and barrier performance of these composites were investigated with SAXS and ASTM E96/E96M-05. Before homogenization, the MMT is agglomerated, while after homogenization it is more exfoliated, which is split up into individual sheets. The water vapor permeability could be reduced by adding up to 20 wt. % montmorillonite and dispersing montmorillonite with two passes in a high-pressure homogenizer. With montmorillonite addition above 20 wt. %, the water vapor permeability started to increase due to aggregation of the montmorillonite in the homogenized composite. At the optimal addition level, the best performance achieved with spraying was a water vapor permeability of 8.3 x 10-12 g/m.s.pa. The air permeability of the composite was evaluated to be less than 0.003 µm/Pa.s. This value confirms an impermeable composite for packaging applications. Considering the orientation of MMT in the composite, the composite’s structure can decide the barrier performance and can be altered by further fibrillation process of cellulose nanofibers via high-pressure homogenization.

Synergistically improve the strength and porosity of carbon paper by using a novel phenol formaldehyde resin modified with cellulose nanofiber for proton exchange membrane fuel cells

To optimize the imbalance between the interfacial bonding and porosity properties of carbon paper (CP) caused by phenol formaldehyde resin (PF) impregnation, and therefore improve the performance of proton exchange membrane fuel cells (PEMFCs), a new approach through cellulose nanofibers grafted with methyl methacrylate (CNFM) as a modified reinforcement and pore-forming agent for PF is investigated. Through suppressing the methylene backbone fracture of CNFM-modified PF during its thermal depolymerization, the interfacial bonding between PF matrix carbon and carbon fibers is enhanced. Compared with unmodified CP, the in-plane resistivity of CNFM-modified CP is reduced by 35.78 %, while the connected porosity increases to 82.26 %, and more homogeneous pore size distribution (PSD) in the range of 20–40 μm is obtained for CNFM-modified CP. Besides, the tensile strength, flexural strength, and air permeability of CNFM-modified CP increase by 72.78 %, 298.4 %, and 103.97 %, respectively. In addition, CNFM-modified CP achieves the peak power density of PEMFCs to 701.81 mW·cm−2, exhibiting 10.98 % improvement compared with commercial CP (632.39 mW·cm−2), evidently achieving an integral promotion of CP and comprehensive performance.

Determination of air permeability of buildings

The air permeability of the building determines the level of energy efficiency of the building. The regions of the European Union are approaching NZEB standards and passive house standards. The Ukrainian regulatory framework for airtightness does not meet European standards for energy-efficient buildings and will require updating, as there will be an increase in the wind permeability of the building, and the increase is possible to the normatively permissible value, increased air permeability and energy efficiency. The permeability is expressed by the value of the air flow in cubic meters per year per square meter of the area of the outer shell of the booth when there is a pressure difference in the internal air of 50 Pa. Ait permeability will need to be specified by parameter q50 [m3/(h·m2)] instead of n50 [h – 1]. All countries of the European Union may use the q50 [m3/(h·m2)] parameter in their standards. Exclusions are Lithuania and Ukraine, where the actual air permeability is determined by the parameter n50 [h – 1]. Based on the Ukrainian standard for air permeability, air permeability is calculated by n50 [h – 1]. For energy efficiency class C, values n50 < 2.0 [h – 1] are allowed, which is approximately the same value as q50 < 5.0 [m3/(h·m2)]. Following the Lithuanian standard, which also corresponds to the vicoristics n50, where n50 < 1.0 h – 1, which is approximately the same value as q50<2.5 [m3/(h·m2)]. It is proposed to establish new standard values for the air permeability and energy efficiency in line with European standards. The results of penetration tests of 24 objects of different heating volumes and energy efficiency classes were analyzed. It’s shown that lovering the energy efficiency class disharmonises the n50 and q50 values. The results allow proposal to set the normative value n50 < 2.5

Smart-Adhesive, Breathable and Waterproof Fibrous Electronic Skins.

For the need of direct contact with the skin, electronic skins (E-skins)should not only fulfill electric functions, but also ensure comfort during wearing, including permeability, waterproofness, and easy removal. Herein, the study has developed a self-adhesive, detach-on-demand, breathable, and waterproof E-skin (PDSC) for motion sensing and wearable comfort by electrospinning styrene-isoprene block copolymer rubber with carbon black nanosheets as the sensing layer and liner copolymers of N, N-dimethylacrylamide, n-octadecyl acrylate and lauryl methacrylate as the adhesive layer. The high elasticity and microfiber network structure endow the PDSC with good sensitivity and high linearity for strain sensing. The hydrophobic and crystallizable adhesive layer ensures robust, waterproof, and detaching-on-demand skin adhesion. Meanwhile, the fiber structure enables the PDSC good air and water permeability. The integration of electric and wearable functions endows the PDSC with great potential for motion sensing during human activities as both the sensing and wearable performances.

Moist air permeability characteristics of flexible contact gaskets used in refrigerators

Flexible contact gasket is a significant component affecting the sealing performance of the refrigerator. However, few studies were conducted on the permeability characteristics of moist air through refrigerator gaskets. The purpose of this study is to explore the permeability characteristics including permeation paths size, flow type, modeling and temperature-humidity-pressure-structure effect. The characteristic scale of the interface of permeation paths is observed as 10−5 m in the free-state by atomic force microscope. The equation of Knudsen number and contact stress relation is established to judgment the flow types. By comparing the critical and simulated contact stresses, it is inferred that moist air simultaneously occurs slip, transition and free-molecular flows. A multi-scale coupling model of permeation rate is constructed to obtain the apparent permeability coefficient characterizing the permeability intensity. The air pressure difference affects the permeability characteristics in the form of direct driving force and changing the contact stress of the interfaces. Free-molecular flow mainly occurs under the negative pressure condition with inhalation coefficient of 2.26 × 10−5∼2.84 × 10−5 m2, while the slip flow mainly occurs under the positive pressure conditions with exhalation coefficient of 2.87 × 10−5∼4.65 × 10−5 m2. The essence of enhancing the sealing performance of structural improvement is to increase the contact stress and length of permeation path. By increasing the height, increasing the inclination angle, adding the auxiliary edges and adding an auxiliary airbag, the inhalation coefficient of moist air, the exhalation coefficient of moist air and the inhalation coefficient of water vapor are decreased by 54.82 %, 51.46 % and 66.04 %.

Spray-assisted layer-by-layer deposition of quaternized chitosan/tannic acid for the construction of multifunctional bio-based nonwoven dressings

Gauze wound dressings have received considerable attention due to their cost-effectiveness, excellent mechanical properties, and widespread applications. However, their inability to actively combat microorganisms and effectively scavenge free radicals results in suboptimal wound management. In this study, a novel nonwoven-based gauze dressing coated with quaternized chitosan/tannic acid (QCS/TA), based on electrostatic interaction and hydrogen bonding, was successfully prepared using a spray-assisted layer-by-layer assembly method. The bio-based nonwoven dressing, assembled with multiple interlacing bilayers, demonstrated outstanding antimicrobial properties, eliminating 99.99 % of Staphylococcus aureus (S. aureus) and 85 % of Escherichia coli (E. coli). Compared to the pristine nonwoven dressing, the QCS/TA-coated nonwoven dressing scavenged >85 % of the surrounding radicals within 2 h. Additionally, the nonwoven dressing exhibits excellent coagulation properties. Notably, the facile spraying procedure preserved most of the softness and breathability of the nonwoven substrate. After the deposition of seven bilayers, the bending stiffness and drape coefficient increased by only 37.63 % and 3.85 %, respectively, while the air permeability and moisture permeability reached 1712 mm/s and 3683.58 g/m2/d, respectively. This bio-based nonwoven dressing, derived from safe and non-toxic ingredients, holds promise as the next generation of multifunctional gauze dressings.

Development of protective fabric systems with spacer fabric and performance evaluation upon hot pressurized steam

Developing new fabric systems with excellent thermal protective performance is essential to protecting workers from hot pressurized steam hazards. In this study, a laminated fabric was selected and a weft-knitted spacer fabric was developed for steam protective fabric systems. Effects of the configuration of the fabric systems and heat setting of spacer fabric on performances were investigated. The results demonstrate that the developed spacer fabric significantly prolonged skin burn times compared with controls. However, heat setting of spacer fabric had a negligible effect on improving thermal protective performance. Spacer fabric provided superior thermal protection while ensuring thermal comfort and enhancing air permeability, especially for spacer fabric after heat setting. Generally, a fabric system composed of a laminated outer shell and a spacer fabric is the best choice for steam protective clothing. The findings help develop a novel thermal liner to decrease energy transfer and provide better protection from pressurized steam.

Dynamic swatch testing of liquid aerosols in a laboratory-sized recirculating wind tunnel

Chemical warfare agents (CWAs) pose a threat as gaseous substances and as liquid aerosols, necessitating chemical warfare-protective clothing for soldiers. The paramount consideration lies in the effectiveness of the clothing as a barrier against the pertinent CWAs. This paper presents a dynamic swatch test method aimed at evaluating the performance of such clothing against liquid-phase aerosol penetration. Central to the methodology is a specialized test cell designed to rotate to the left and right, integrated within a laboratory wind tunnel, replicating mission-relevant conditions with varying wind speeds. Utilizing di(2-ethylhexyl) sebacate particles as liquid aerosols, tests were conducted at wind speeds of 1.0, 3.0, and 5.0 m/s. Penetration assessment relied on analyzing particle counts downstream and upstream of the fabric, with preliminary studies showing that higher wind speeds and fabric air permeabilities increase penetration at an equivalent face velocity of 5.0 cm/s. Interestingly, penetration decreased when fabric samples were subjected to rotation. The system and methodology devised demonstrated consistent and repeatable results, offering valuable insights into optimizing the effectiveness of chemical warfare-protective clothing. This research contributes to advancing methodologies for testing protective clothing, crucial for ensuring the safety of military personnel in hazardous environments.

A flexible and breathable ammonium polyphosphate/chitosan/MWCNT doped PEDOT:PSS coating decorated carbon cloth for high-efficiency flame retardancy and electromagnetic interference shielding applications

There is an urgent need for versatile textiles for different applications due to the rapid development of flexible and wearable electronic devices. However, the poor breathability, high cost, and complex manufacturing processes are still urgent issues to be addressed. In this work, a breathable and flexible carbon cloth (CC) decorated multifunctional coatings (ACMPP) is developed through a facile and scalable coating technology for flame retardancy and electromagnetic interference (EMI) shielding applications. The ACMPP are constructed by incorporating the ammonium polyphosphate/chitosan/multi-walled carbon nanotubes (ACM) composites with core-multi-shell structure into PEDOT:PSS (PP). The low-cost ACM composites demonstrate the promising potential to substitute complex manufacturing processes with an easy electrostatic self-assembly. The as-obtained ACMPP/CC composites display favorable air permeability (69.65 mm·s-1), efficient water vapor transmittance (273.17 kg·m-2·d-1), and high-efficiency flame retardancy (36.8 % of limiting oxygen index), coupled with excellent EMI shielding capacity (59.36 dB in the X band) and shielding stability. The simplicity and scalability of the approach in this work offers a highly cost-performance paradigm to construct next generation flexible textiles for flame retardancy and electromagnetic interference shielding applications.

Scalable thermochromic superhydrophobic collagen fiber-based wearable materials for all-weather self-adaptive radiative cooling and solar heating

As traditional biomaterials for wearables, collagen fibers (CFs)-based products are widely used in daily life due to their exceptional performance. However, developing CFs-derived products that exhibit seasonal self-adaptive temperature regulation to satisfy the thermal comfort for humans and prolong their service life remains a significant challenge in practical applications. Herein, the smart temperature-adaptive superhydrophobic radiative cooling CFs (STSRC-CFs) were created through a nanoengineering design strategy by a simple and scalable layer-by-layer spraying method. The STSRC-CFs inherit the outstanding properties of natural CFs and maintain high tensile strength (18.2 MPa), air permeability (38.2 mL/cm2∙h), and superhydrophobicity (CA of 161.1°, SA of 2.0°). Moreover, STSRC-CFs possessed a thermal emittance of 0.94, while the solar reflectance could be dynamically modulated in response to the ambient temperature change with a solar reflectance of 0.91 at high temperatures and 0.81 at low temperatures. The synergic effect enables STSRC-CFs to autonomously manage radiative cooling and solar heating, thereby achieving intelligent energy-saving temperature regulation for winter warming and summer cooling. Notably, the superhydrophobic self-cleaning effect of STSRC-CFs prevents from contamination, ensuring sustained spectral modulation and intelligent temperature regulation. Serving as a proof-of-concept for intelligent self-adaptive passive temperature regulation, the STSRC-CFs introduced in this study lay the groundwork for the development of advanced temperature-adaptive radiative cooling and solar heating functional materials.

Performance enhancement of reactive foam dyeing for cotton fabric through different foaming agents and stabilizers

Purpose In the textile dyeing industry, the foam dyeing has been recognized as a significantly sustainable alternative for the cotton fabrics. However, this efficient technology undergoes the many issues related to the foam generation, foam optimization and the required performance of the resultant fabrics. The purpose of this paper is to address these issues through the development and optimization of the novel reactive foam dyeing recipes for the cotton fabrics. Design/methodology/approach The foam dyeing recipes were generated and optimized using the different stabilizers, foaming agents and three primary colors of reactive dyes. The different recipes were applied onto the cotton fabric using laboratory scale foam coating machine. The performance of the foam coated and padded fabrics was evaluated using different criteria including the shade depth, rubbing fastness, air permeability, washing fastness, perspiration fastness, light fastness and tear strength. Then, a complex decision-making approach, namely, analytic hierarchy process (AHP), was applied for the ranking of the key recipes based on the main criteria. Findings The newly optimized foam dyeing recipes were found very competitive with the conventional pad dyeing process with respect to the shade-depth and the other performance properties. The optimization of foaming parameters and addition of stabilizers have advanced the foam dyeing process, which would accelerate the implementation of foam dyeing methods in the textile industry. Furthermore, significant water and energy savings would be achieved as compared to the conventional foam dyeing. AHP model offered a comprehensive and rational way to identify the most important recipes amongst the selected recipes. Originality/value In this research, novel foam dyeing recipes have been developed for the cotton fabrics through the optimization of the different stabilizers, foaming agents and the three primary colors of reactive dyes. Until now, the exiting literature has not reported the combination of these stabilizers with the different foaming agents and three primary reactive dyes for the improvement of sustainable foam cotton dyeing process.

Mechanically robust superhydrophobic and oleophobic nanofiber membranes with breathability, solvent-resistance, and high-temperature-resistance

Protective materials that can ensure the safety of personnel and equipment in extreme environments have a wide range of application prospects, such as outdoor protective clothing, fire-fighting clothing, etc. However, designing such highly functional materials is still considered a long-standing challenge. Herein, the superhydrophobic and oleophobic fibrous membranes (SOFM) prepared by electrospinning, heat treatment and spraying techniques, endowing the fibrous membranes with good thermal stability, air permeability and outstanding repellence to liquids such as water, oil and low surface energy solvents. The developed SOFM exhibits integrated properties with ethanol intrusion pressure of 0.75 KPa, excellent air permeability of 1.54 mm/s, water vapor transmission rate of 7.99 kg·m−2·d-1, high thermal decomposition temperature of 330 ℃, tensile strength of 9.2 MPa. Therefore, SOFM can effectively protect people and equipment in extreme environments. This work may contribute to the design of fiber materials with higher protection levels in the field of protective clothing.

Numerical calculation of air permeability of warp-knitted jacquard spacer shoe-upper materials based on CFD

Abstract In order to realize the rapid design of warp-knitted jacquard spacer shoe-upper materials and to explore the influence of different fabric surface organization structures on their air permeability, it is proposed to numerically simulate the air permeability performance of jacquard shoe-upper materials using ANSYS fluid analysis. First, four kinds of shoe material specimens with different upper and lower layer mesh alignment relationships are designed and tested, then the corresponding geometric structure models of the fabric are established based on the samples and appropriately processed, and finally the air permeability of the shoe material is numerically simulated and calculated based on computational fluid dynamics. The results show that, under the same conditions, the air permeability of double-sided mesh structure is significantly better than that of single-sided mesh structure, and its air permeability can be optimized by adjusting the relationship between the upper and lower layers of the fabric mesh; the airflow mainly passes through the fabric pores and gaps between the yarns, and the closer the fabric structure is, the more the air flow is hindered, and the worse the air permeability is. The simulation results of the established numerical model are consistent with the measured results, and the error is less than 10%, so it can be used to simulate and predict the air permeability of the warp-knitted jacquard spacer footwear materials, and provide theoretical support for the design and performance research of footwear materials.

Ultrasensitive electrospinning fibrous strain sensor with synergistic conductive network for human motion monitoring and human-computer interaction

With the rapid development of wearable electronic skin technology, flexible strain sensors have shown great application prospects in the fields of human motion and physiological signal detection, medical diagnostics, and human-computer interaction owing to their outstanding sensing performance. This paper reports a strain sensor with synergistic conductive network, consisting of stable carbon nanotube dispersion (CNT) layer and brittle MXene layer by dip-coating and electrostatic self-assembly method, and breathable three-dimensional (3D) flexible substrate of thermoplastic polyurethane (TPU) fibrous membrane prepared through electrospinning technology. The MXene/CNT@PDA-TPU (MC@p-TPU) flexible strain sensor had excellent air permeability, wide operating range (0–450 %), high sensitivity (Gauge Factor, GFmax = 8089.7), ultra-low detection limit (0.05 %), rapid response and recovery times (40 ms/60 ms), and excellent cycle stability and durability (10,000 cycles). Given its superior strain sensing capabilities, this sensor can be applied in physiological signals detection, human motion pattern recognition, and driving exoskeleton robots. In addition, MC@p-TPU fibrous membrane also exhibited excellent photothermal conversion performance and can be used as a wearable photo-heater, which has far-reaching application potential in the photothermal therapy of human joint diseases.

The impact of arable soil management on physical functions – The ratio of air capacity and air permeability or hydraulic conductivity as a document of harmful soil compaction

Soil health or soil degradation criteria are until now not well documented for a greater number of soil profiles under conventional and conservation tillage management in the literature. In order to evaluate the compaction status of more than 700 arable sites analyzed within the last 40 years, the Compaction Verification Tool (CVT) was applied according to Zink et al. (2011). Besides the ratio of air capacity (AC, at a matric potential of −6 kPa) and saturated hydraulic conductivity (Ks), the ratio of AC and air conductivity (Ka, at a matric potential of −6 kPa) was considered for evaluating the compaction status with respect to potentially harmful soil alterations. The compaction status was classified into the CVT classes I–IV, where a harmful subsoil compaction was assumed, if both values of AC and Ks or AC and Ka simultaneously exceeded (are smaller than) their defined critical value indicating limited conditions for plant growth (CVT class IV). We analyzed the compaction status of soil profiles with respect to clay content, soil type, structural stage (aggregate forms) and time span of sampling (1980–1999, 2000–2020) under conventional and conservation tillage for top- and subsoil horizons. While also some of the annually plowed topsoils under conventional tillage showed critical values of AC, Ks and Ka, the occurrence of harmful soil compaction is most dominant in the subsoil horizons (> 30 cm depth) because of a higher proportion of class IV which increased with the clay content (from < 12 % to > 12 % clay), irrespective of the applied ratio used for verification (AC/Ks or AC/Ka). Especially the highly productive Luvisols showed a high percentage of harmful compaction in the subsoil (30–41 % in CVT class IV). Soil profiles under conservation tillage management are less affected by harmful compaction. The more aggregated subsoils showed smaller proportions of class IV, which was further influenced by the clay content.

Analysis of the regulatory and legislative base of Ukraine and the European experience in conducting energy audits of buildings

The article analyzes the regulatory and legislative base for the energy efficiency of buildings. It identifies the main areas for improving energy efficiency by improving the process of energy audit, as well as improving the system of indicators that determine the airtightness of the building and preservation of comfortable conditions for human stay in the room. The relevance of the work is determined by the problem of low energy efficiency of the housing stock of Ukraine, which affects the rational consumption of energy, necessitates the introduction of various measures aimed at rationalizing energy use in general and buildings in particular, setting maximum permissible energy consumption rates for buildings and strengthening relevant control. The imperfection of the regulatory and legislative base in the field of energy efficiency, the need to develop a state standard for the design of buildings with increased air permeability, the development of a methodology for determining the air permeability of a building, the legislative establishment of minimum requirements for building airtightness, the development of a methodology for testing buildings for airtightness, and the imperfection of the methodology for conducting an energy audit of a building form the basis for further research. To improve the energy management of buildings, it is proposed to introduce mandatory testing of the building for airtightness, which will standardize approaches to energy management and compliance with the relevant requirements for building airtightness will lead to an increase in the energy efficiency class of buildings. Keywords: energy efficiency, energy audit, air permeability, airtightness.

A New Method for Evaluating the Homogeneity within and between Weave Repeats in Plain Fabric Structures Using Computer Image Analysis.

This article introduces a novel, rapid, and non-destructive method for assessing homogeneity within and between weave repeats in fabric structures, termed intra-repeat (IAR) and inter-repeat (IER) evaluation. The method focuses on structural parameters, including inter-thread pores (ITPs) and warp and weft pitches, using computer image analysis. Each parameter is assigned to a module in the repeat weave pattern, facilitating the sorting of modules in the IAR and IER fabric structure arrangement. The method was verified using artificial images and 30 real plain fabrics with varying degrees of warp grouping, employing the author's proprietary software, MagFABRIC version 2.1The general measurable coefficients of intra- and inter-homogeneity were defined and related to the airflow measurements of these fabrics. Multiple regression models of airflow revealed strong dependencies, particularly for F = 10, with the size, shape, and position of ITPs and warp and weft pitches showing significant correlation. These findings underscore the importance of the new homogeneity parameters in textile structure analysis, including both IAR and IER woven fabric structure homogeneity parameters. The research aims to model specialized fabrics (e.g., barrier, filtration, composite fabrics) to address local changes in fabric structure affecting properties such as filtration efficiency, air permeability, and mechanical properties, especially in applications like composites or medical implants.

Unveiling enhanced sound absorption in coconut wood through hemicellulose and lignin modification

Coconut wood (Cocos nucifera L.) is lightweight and has variable quality, making it a potential candidate for manufacturing sound absorption boards. However, its sound absorption coefficient needs enhancement to optimize its effectiveness in this application. This study aims to enhance its sound absorption properties using eco-friendly hydrogen peroxide and acetic acid treatments. This treatment modified the carbohydrate polymers (hemicellulose and cellulose) and lignin structures in the wood cell wall. The novelty of this approach lies in using these chemicals to improve acoustic performance significantly. Coconut wood samples were treated with a 1:1 acetic acid and hydrogen peroxide mixture for 20, 40, 60, and 80 min. Characterization techniques such as FTIR, XPS, and XRD, and 3D optical profilometry analyzed changes in chemical functionalities, crystallinity, and surface roughness. Sound absorption coefficients were measured using the impedance tube method. Results showed a significant improvement in sound absorption for all treated samples, especially at 60 min. The treatment also enhanced surface roughness, air permeability, porosity, and pore sizes, contributing to better sound absorption. This proposed treatment method addresses environmental consciousness and enhances the sustainable use and utilization of coconut wood.

Biomechanical design optimization and experimental verification of Bezier curve based two-sectional cervical pillow with variable-density cellular structure

The fundamental function of an optimal cervical pillow is to provide sufficient support to maintain normal spinal alignment and minimize biological stress on the contact surface throughout sleep. The recent advancements in cervical pillows have mainly focused on the subjective and objective evaluations of support comfort, as well as the relationship between pillow height and cervical vertebrae posture. However, only a few studies have addressed shape design guidelines and mechanical performances of the pillows themselves. In this study, a two-sectional contour cervical pillow comprising an arc and a Bezier curve is designed to support the head and neck. The design of the arc-shaped neck section incorporates the Cobb’s angle and Borden value from healthy individuals to reflect the consistency of normal cervical anatomical features. The Bezier curve-based head section takes the head length and neck depth into account as significant individual differences. Static analysis and lattice optimization are performed in ANSYS Workbench to develop a variable-density cellular structure, aimed at improving air permeability and reducing the risk of pressure ulcers associated with the cervical pillow. The rapid prototyping technique fused deposition modeling (FDM) and thermoplastic material polylactic acid (PLA) are employed for fabricating different cellular structures. The results demonstrate that the neck section experiences less stress and greater deformation in comparison to the head section, indicating good comfort and support provided by the designed cervical pillow. Additionally, the compressive, bending, and cushion properties of the 3D-printed cervical pillow with variable-density cellular structure are experimentally validated, further confirming its effectiveness.

Application of New Polymer Soil Amendment in Ecological Restoration of High-Steep Rocky Slope in Seasonally Frozen Soil Areas.

In seasonally frozen soil areas, high-steep rocky slopes resulting from open-pit mining and slope cutting during road construction undergo slow natural restoration, making ecological restoration generally challenging. In order to improve the problems of external soil attachment and long-term vegetation growth in the ecological restoration of high-steep rocky slopes in seasonally frozen areas, this study conducted a series of experiments through the combined application of polyacrylamide (PAM) and carboxymethyl cellulose (CMC) to assess the effects of soil amendments on soil shear strength, water stability, freeze-thaw resistance, erosion resistance, and vegetation growth. This study showed that the addition of PAM-CMC significantly increased the shear resistance and cohesion of the soil, as well as improving the water stability, freeze-thaw resistance, and erosion resistance, but the internal friction angle of the soil was not significantly increased after reaching a certain content. Moderate amounts of PAM-CMC can extend the survival of vegetation, but overuse may cause soil hardening and inhibit vegetation growth by limiting air permeability. It was observed by a scanning electron microscope (SEM) that the gel membrane formed by PAM-CMC helped to "bridge" and bind the soil particles. After discussion and analysis, the optimum application rate of PAM-CMC was 3%, which not only improved the soil structure but also ensured the growth of vegetation in the later stage under the optimum application rate. Field application studies have shown that 3% PAM-CMC-amended soil stably attaches to high-steep rocky slopes, with stable vegetation growth, and continues to grow after five months of freeze-thaw action, with no need for manual maintenance after one year.