Nonwoven Fabric Layer Research Articles

Tri-Layer Nonwoven Separator with Thermal Shutdown Function Fabricated through a Facile Papermaking Method for High-Safety Lithium-Ion Battery

Lithium-ion batteries have long been plagued by the safety issue of thermal runaway. Improving the thermal stability and developing the thermal shutdown function of the separators are considered reliable solutions. Therefore, in this work, a tri-layer structured nonwoven separator with a thermal shutdown function has been prepared via the papermaking method. The separator comprises a polyethylene fiber layer, a microfibrillated cellulose fibers layer, and a polyethylene terephthalate nonwoven fabric layer. The polyethylene fiber layer endows the separator with a thermal shutdown function at 135 °C. The middle polyethylene terephthalate nonwoven layer provides support, while the microfibrillated cellulose fibers adjust the pore size. The separators exhibit excellent thermal stability, no shrinkage after heat treatment at 200 °C, and a wide thermal shutdown temperature window, thereby enhancing battery safety. This research provides an approach to fabricating high-safety thermal shutdown separators.

How do three-layer surgical masks prevent SARS-CoV-2 aerosol transmission?

The three-layer surgical mask was recognized by the World Health Organization as an effective-protection tool for reducing SARS-CoV-2 transmission during the COVID-19 pandemic; however, the contribution of each layer of this mask to the particle size–dependent filtration performance resistance remains unclear. Here, both experimental work and numerical simulation were conducted to study the role of each mask layer in particle size–dependent filtration and respiratory resistance. By using scanning electron microscopy images of a commercial three-layer mask, composed of two spun-bond and one melt-blown nonwoven polypropylene fabric layers, four representative models were constructed, in which the computational fluid dynamics of multiphase flow were performed. The pressure drop of all models under different flow conditions was measured next. Numerical simulation was then verified by comparing the experimental results in the present study and other theoretical works. The filtration efficiency of the spun-bond polypropylene nonwoven fabric layer was much lower than that of the melt-blown nonwoven polypropylene fabric layer for the particle diameter in the range of 0.1–2.0 μm. Both the spun-bond and melt-blown nonwoven polypropylene fabric layers demonstrated extremely low filtration efficiency for particles was<0.3 μm in diameter, with the maximum filtration efficiency being only 30%. The present results may facilitate rational design of mask products in terms of layer number and structural design.

Microstructural evaluation and recommendations for face masks in community use to reduce the transmission of respiratory infectious diseases

Background and ObjectiveRecommendations for the use of face masks to prevent and protect against the aerosols (≤5µm) and respiratory droplet particles (≥5µm), which can carry and transmit respiratory infections including severe acute respiratory syndrome coronavirus (SARS-CoV-2), have been in effect since the early stages of the coronavirus disease 2019 (COVID-19). The particle filtration efficiency (PFE) and air permeability are the most crucial factors affecting the level of pathogen transmission and breathability, i.e. wearer comfort, which should be investigated in detail. MethodsIn this context, this article presents a novel assessment framework for face masks combining X-ray microtomography and computational fluid dynamics simulations. In consideration to their widespread public use, two types of face masks were assessed: (I) two layer non-woven face masks and (II) the surgical masks (made out of a melt-blown fabric layer covered with two non-woven fabric layers). ResultsThe results demonstrate that the surgical masks provide PFEs over 75% for particles with diameter over 0.1µm while two layer face masks are found out to have insufficient PFEs, even for the particles with diameter over 2µm (corresponding PFE is computed as 47.2%). Thus, existence of both the non-woven fabric layers for mechanical filtration and insertion of melt-blown fabric layer(s) for electrostatic filtration in the face masks were found to be highly critical to prevent the airborne pathogen transmission. ConclusionsThe present framework would assist in computational assessment of commonly used face mask types based on their microstructural characteristics including fiber diameter, orientation distributions and fiber network density. Therefore, it would be also possible to provide new yet feasible design routes for face masks to ensure reliable personal protection and optimal breathability.

Intelligent safeguarding Leather with excellent energy absorption via the toughness-flexibility coupling designation

High-performance intelligent body armors with both soft wearability and good energy absorption are increasingly required in modern social life. Leather, a breathable, pliable, and tough natural material has extensive applications in the anti-impact field. In this study, a multifunctional Leather/CNT-SSG/PU sandwich structure with high energy absorption and excellent sensing monitoring properties is designed by integrating tough leather and flexible conductive shear stiffening gel (CNT-SSG). The maximum force dissipation capacity of the Leather/CNT-SSG/PU reaches 84 % in the drop hammer test and the limit penetration velocity up to 142.4 m/s in the ballistic test. Moreover, the Leather/CNT-SSG/PU exhibits excellent stress wave dissipation properties due to the hierarchical structure. By introducing the interdigital electrode array on the non-woven fabric layer, a bulletproof vest (Leather/CNT-SSG/NWF) with intelligent anti-impact performance and in situ monitoring behavior is successfully achieved. This toughness and flexibility coupling designation provides a novel method for next-generation soft body armor.

Electrospun membranes filtering 100nm particles from air flow by means of the van der Waals and Coulomb forces.

Nonwoven fibrous filter membranes are widely used in filtration because of their low cost. They are less effective in intercepting airborne particles of the order of 100nm, which is of the SARS-CoV-2 (COVID-19) virus's size. Many diseases, including COVID-19, predominantly spread by droplets released by breathing, coughing, sneezing, or medical procedures. It was shown that the smallest droplets can evaporate in air before settling, thus, making viruses airborne and easily penetrating even the best masks and filters. As a result, air-filtering membranes, which are capable of effective interception of ∼100nm nanoparticles are highly desirable. A traditional way to improve filtration efficiency by overlapping several layers of nonwoven fabrics increases the required pressure drop, and thus, should be avoided as much as possible. Here, we propose and demonstrate an innovative approach to enhance performance of filtration membranes based on (i) a dramatic reduction in the fiber size, and (ii) metal coating of the fibers. The first component of this approach allows one to incorporate a novel physical mechanism of filtration, the short-range van der Waals forces, whereas the second one adds the long-range electric Coulomb forces if the oncoming nanoparticles are pre-charged and the metal-plated membrane grounded. In the present work, the ∼100nm aluminum nanoparticles are filtered as a model of commensurate airborne single COVID-19 viruses, and Platinum is used as the sputter-coated material for the fiber coating. The resulting filtration efficiency enhanced by the electric Coulomb forces alone is increased by the factor of 1.77, while the filtration efficiency additionally facilitated by the van der Waals forces increased by the factor of 2.44. In comparison to the filter membranes with ∼500nm fibers without the electric forces involved, the van-der-Waals-electric filter membrane with fibers ∼90nm is 2.24 1.77=3.96 times more effective. The quality factor of a membrane which combines the van der Waals and Coulomb forces is 10.6 psi-1, which is almost three times that of a comparable membrane without the electric Coulomb force (with only van der Waals forces being used).

Bioactive Composite Nonwoven Surgical Dressing based on Cellulose Coated with Nanofiber Membrane using the layer-by-layer technique

Nonwoven fabric with cellulosic base has many Features ability to absorb biological fluids and can easily adapt for different types and locations of wounds, which made it common and unique in surgical dressing. The study aimed To design different samples made of one layer and two layers of nonwoven fabrics for the inner layer of deep endoscopic wound dressings to control the biological fluid leakage. 100% cotton, 100% viscose, and viscose/polyester (70:30) % were used as one layer samples, and every two different materials were used interchangeably to design the two-layer (layer-by-layer) samples. One-layer samples were dyed using green coffee extraction, while the two layers samples were enhanced by adding powdered green coffee between them, as an innovative use in the surgical dressing applications. Electrospinning technique was used to form a delicate membrane of Ciprofloxacin (CIP) antibiotic and Kylie Collagen to coat the single-layer samples without coffee dyeing to compare their performance with the dyed samples. Also, for comparing the results of the two layers samples that were enhanced with green coffee powder with and without the coating nanofibers membrane. Designed samples were evaluated by mechanical and physical properties for nonwoven fabrics, in addition, FTIR, SEM, absorbency and antimicrobial activity, and K/S especially for dyed samples, finally cytotoxicity for CIP, Kylie collagen, and green coffee. The results were pointed to that the dyed one-layer samples with green coffee extraction achieved a high-performance function for air permeability and antimicrobial activity. While the layer-by-layer samples that enhanced adding green coffee powder showed improvement for strength, absorbency properties, and antimicrobial activity, especially for the samples made of cotton/ viscose layers, and viscose/ viscose blended polyester layers, followed by the sample of cotton/ viscose blended polyester layers that were coated with 0.1wt% CIP antibiotic and Kylie Collagen membrane

Thermal behaviour of waterproof coated fabrics and identification of chemical groups present in melt-blown polyester non-woven fabrics coated with waterproof acrylic polymer binder

Polyester non-woven fabrics are a good choice for base material in development of engineered waterproof fabrics. They find wide applications in bathroom floor lining, Roof lining, Car floor lining and many such applications. These fabrics not only provide strength and durability to the structure but also enhance the thermal as well as shelf-life of the structure. The presence of Chemical groups like ethylene functional group which is a chemical compound prominently present in polyester and observation of strong peaks of polyester functional groups aids in robust behaviour of the waterproof coated fabrics. These chemical groups present in the waterproof acrylic polymer binder also influences the development of durable fabrics with good hardness values. In this research a waterproof fabric for such applications is developed using a non-woven polyester fabric as the base material and roller coating process. The changes in the surface morphology of the fabrics is recorded and analysed using SEM micrographs. However, the analysis of thermal properties of these coated fabrics using DSC, TG/DTA instruments show melting of the coated material at 375 °C and TGA graphs show degradation of material occurring at 400 °C. The density measurement results show the fabrics ability to achieve lower values when nonwoven fabric layers are doubled which may be due to consumption of less binder and locking of air between layers. The Rockwell hardness results of 31.4 HRB (B scale) for single layer and 68.2 HRB for double layer proves the performance of the coated fabric at par with soft steel. The coated fabrics show zero air porosity when tested under air-permeability tester. The process of roller coating proves to be robust method of application of water proof polymer binder on non-woven fabrics.

Morphology of Thin Film Composite Membranes Explored by Small-Angle Neutron Scattering and Positron-Annihilation Lifetime Spectroscopy.

The morphology of thin film composite (TFC) membranes used in reverse osmosis (RO) and nanofiltration (NF) water treatment was explored with small-angle neutron scattering (SANS) and positron-annihilation lifetime spectroscopy (PALS). The combination of both methods allowed the characterization of the bulk porous structure from a few Å to µm in radius. PALS shows pores of ~4.5 Å average radius in a surface layer of about 4 μm thickness, which become ~40% smaller at the free surface of the membranes. This observation may correlate with the glass state of the involved polymer. Pores of similar size appear in SANS as closely packed pores of ~6 Å radius distributed with an average distance of ~30 Å. The main effort of SANS was the characterization of the morphology of the porous polysulfone support layer as well as the fibers of the nonwoven fabric layer. Contrast variation using the media H2O/D2O and supercritical CO2 and CD4 identified the polymers of the support layers as well as internal heterogeneities.

Silica aerogel-integrated nonwoven protective fabrics for chemical and thermal protection and thermophysiological wear comfort

This research has designed and prepared a protective clothing layer by integrating porous silica aerogel with nonwoven fabrics for simultaneous chemical and thermal protection. Protective interlining having resistance to heat and liquid chemical penetration was developed by sandwiching randomly distributed aerogel particles between viscose nonwoven fabric layers. The nonwoven layer and aerogel particle layer were explored by analysing fabric surface morphology. Physical characterization of the test specimens revealed that the weight and thickness of fabric increased after the integration of aerogel particles. Consequently, improved chemical resistance and thermal resistance were observed in the aerogel–nonwoven fabrics with higher aerogel concentration. For clothing comfort, the high air permeability indicated sufficient breathability by transferring air and water vapour from the body to the atmosphere and vice versa through apparel. Improved evaporative transmittance and cooling index of aerogel–fabrics suggested that the fabric will create a favourable thermal comfort microenvironment between the skin and apparel. For wear comfort regarding wet clinginess, the high water uptake and evaporation rate of the fabric specimens indicated their ability to retain and evaporate large amounts of perspiration vapour in a hot and humid atmosphere. The overall performance of the aerogel–nonwoven fabrics suggested that the integration of silica aerogel with viscose nonwoven fabric is a prospective approach for developing protective interlining that will provide reliable chemical and thermal protection as well as adequate clothing comfort to the wearer.

A radio absorbing composite material based on compounded rubber and modified nonwoven fabric

The paper discusses the relationship between the reflection of microwave electromagnetic radiation and the composition of a composite multilayer material made from rubber filled with carbonyl iron particles and nonwoven fabric reinforced with carbon fiber. It is found that the radio absorbing composite material has low reflectivity at electromagnetic wave frequencies less than 4 GHz. It is shown that the composite material has the highest absorption capacity when electromagnetic waves are incident on the nonwoven fabric layer of the material.

3D morphology design for forward osmosis

We propose a multi-scale simulation approach to model forward osmosis (FO) processes using substrates with layered homogeneous morphology. This approach accounts not only for FO setup but also for detailed microstructure of the substrate using the digitally reconstructed morphology. We fabricate a highly porous block copolymer membrane, which has not been explored for FO heretofore, and use it as the substrate for interfacial polymerization. The substrate has three sub-layers, namely a top layer, a sponge-like middle layer, and a nonwoven fabric layer. We generate a digital microstructure for each layer, and verify them with experimental measurements. The permeability and effective diffusivity of each layer are computed based on their virtual microstructures and used for FO operation in cross-flow setups at the macro-scale. The proposed simulation approach predicts accurately the FO experimental data.

Preparation and Characterization of Structural Damping Composites Toughened by Polyamide Nonwoven Fabrics

A new kind of structural damping composites was prepared by interleaving polyamide nonwoven fabrics (PNF) between the carbon fiber reinforced epoxy composite laminates. The damping behaviors of the composites made were experimentally investigated using cantilever beam test and dynamic mechanical analysis. The damping ratios of the nonwoven fabrics interleaved composites were compared with the ones of non-interleaved composites. In addition, the interlaminar shear strength and flexible modulus of the composites were also investigated, as well as the composite compression after impact (CAI), Mode I and Mode II interlaminar fracture toughness (GIC and GIIC), in order to evaluate the influence of the polyamide nonwoven fabric layers on the composite mechanical properties. It has been observed that the interleaved polyamide nonwoven fabric layers greatly improved the composite damping loss factors, and the composites containing 7 layers of PNF showed the best damping behavior. Meanwhile, the addition of PNF showed a negligible influence on the composite flexible strength and modulus and interlaminar shear strength. Most importantly, the CAI, GIC and GIIC tests indicated that the composite interlaminar toughness and impact resistance were significantly improved by the interleaved PNF. Finally, the reinforcing mechanism of this kind of composites is discussed.

Experimental and numerical analysis on Mode-I delamination of CFRP laminates toughened by polyamide non-woven fabric layer

The objective of this research is to put forward a toughening method by using the polyamide non-woven fabric (PNF) and investigate the Mode-I fracture toughness and delamination characteristic of the toughened CFRP laminates by performing the double cantilever beam test. The effect of PNF interlayer, which is formulated by a bilinear cohesive zone model, on the Mode-I fracture of U3160-PNF/3266 laminated composites is numerically analyzed. And the intralaminar damages are considered by using strength criteria and stiffness degradation law. The influences of PNF/3266 interlayer strength, U3160/3266 laminate thickness and initial crack length on the mechanical response of laminates are studied systematically. The work by combining the experiment and simulation is helpful for the optimal design of laminated composites used in aerospace and civil engineering.

Novel polysiloxaneimide/polyetherimide/non-woven fabric composite membranes for organophilic pervaporation

In this study, a novel composite membrane using polysiloxaneimide (PSI) as a selective layer was developed for hydrophobic pervaporation. The PSI was synthesized from 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA) and amino-modified siloxane (dual-end type). The physiochemical characterization of the PSI using FTIR, NMR and XRD confirmed the success of the synthesis. A non-woven fabric layer covered by a crosslinked porous polyetherimide (PEI) layer was used as a support for the composite membrane. The PSI layer was formed by non-solvent induced phase inversion. The effects of temperature in pervaporation, as well as the preparation conditions in terms of the support layer structure, PSI dopant solution composition and post treatment on the pervaporation performance of the composite membranes were investigated. The pervaporation test for recovering ethanol from its aqueous solution (5wt%) at 60°C showed that the highest separation factor obtained with the composite membrane was ~3, and the corresponding flux was ~0.5kg/m2h.

Processing Technique and Property Evaluation of Stab-Resistant Composite Fabrics

In this research, the nonwoven fabrics were made of 50 % high-tenacity polyester fiber and 50 % low melting polyester fiber, after which the nonwoven fabrics were thermal-treated at 110 °C, 120 °C, 130 °C, 140 °C and 150 °C for 1 min, 2 min, 3 min, 4 min and 5 min. Next, two layers of nonwoven fabrics were laminated with a layer glass (GF) fiber plain fabric or a layer of Nylon 66 grid, forming the sandwich structure. The nonwoven/ GF composite fabrics and the nonwoven/ Nylon 66 grid composite fabrics were also reinforced by needle-punching and thermal treatment, after which the two composite fabrics were measured with tensile strength and stab-resistant strength. Meanwhile, two layers of nonwoven fabrics needle-punched served as the control group. According to the results, Nylon 66 grid and glass fibers plain fabrics were both good at strengthening, the former reinforced the tensile strength of the composite fabrics and the later heightened the stab-resistant strength of the composite fabrics.

Manufacturing and Properties of Fire-Retardant and Thermal Insulation Nonwoven Fabrics with FR-Polyester Hollow Fibers

Abstract In this study, nonwoven fabrics were manufactured using flame-retardant polyester (PET) hollow fibers (FR-PET fibers) and low-melting-temperature PET fibers (low- Tm fibers) for use as thermal insulation. Four nonwoven fabrics with different process routes were utilized to manufacture loose nonwoven fabric (LNF), thermal pressed nonwoven fabric (PNF), needle-punched and thermal pressed nonwoven fabric (NPNF), and needle-punched and through-air thermal bonded nonwoven fabric (NTNF). Thermal conductivity of these four nonwoven fabrics was assessed. Furthermore, LNFs were created using various thermal pressing temperatures (100, 120, 140, 160, 180, and 200°C), low- Tm fiber contents (10, 20, 30, 40, and 50%), and number of layers of nonwoven fabrics (1, 2, 3, 4, and 5 layer) to assess tensile strength, thermal conductivity, and the limiting oxygen index (LOI). Experimental results demonstrate that LNF had a low thermal conductivity of 0.5962 W/mK and the LOI of LNF was 35%.

Processing conditions of abrasion and heat resistance for hybrid needle-punched nonwoven bag filters

Abstract Two nonwoven fabrics and a polyester grid (C) were laminated together to form nonwoven composite for use as filter bags. One nonwoven composite (A) was with polyester fibers of various levels of fineness and with low melting-temperature ( T m ) polyester fibers on the surface layer; the other (B) was made of 2.22 dtex polyester fibers. The nonwoven composites were laminated together with the grid in an A/B/C/B order to form a sandwich structure with a constant basic weight of 500 g/m 2 , thermal calendared and needle punched to bond the layers in the fabricated composite nonwoven fabrics. The physical properties of the filter at different conditions are discussed. The specify type results demonstrated that the filter's heat shrinkage ratio was less than 2%, and its shrinkage ratio in the longitudinal direction (also called machine direction (MD)) was lower than that in the transverse direction (also called cross-machine direction (CD)) perpendicular to the MD when the thermal pressing temperature was less than 130 °C. The abrasion resistance for the surface layers of the nonwoven fabrics increased when basic weight and thickness increased. When the basic weight of the surface layers of nonwoven fabrics was increased from 50 to 100 g/m 2 , the abrasion resistance increased from 10 to 70%. When the filter thickness was 1.8 mm, the degree of abrasion resistance increased by roughly 20–30% over that for the filter of 1.2 mm thick.

Modeling on Mechanical Properties of Polishing Pads in CMP Process

ABSTRACTChemical mechanical polishing is an essential process for achieving a high degree of planarization. The planarity after CMP sensitively depends on pattern scales, pattern densities and mechanical properties of polishing pads. In order to simulate the topography after CMP, a numerical model for the polishing pad is proposed. In this model, the surface roughness layer of the polishing pad is assumed as a flat soft layer. The distribution of the contact pressure between the patterned wafer and the polishing pad is calculated with finite element method, and the pattern topography is modified based on the pressure dependency of the polishing rate. The iterations of the contact pressure analyses and the topography modifications give the progress of the polishing process numerically. The model is applied to oxide CMP process with silica slurry and stacked pad of polyurethane and non-woven fabric. The compressive elastic moduli of polyurethane layer and non-woven fabric layer are measured dynamically. The elastic modulus of the soft layer is treated as a fitting parameter between the experimental results and the numerical model. The models with the elastic modulus of 10 MPa for the soft layer show good agreements with the experimental results in both of a short range, where the compressive deformation of the pad is dominant, and a long range, where the bending deformation is dominant. Static measurements for the surface elasticity of the polyurethane layer also give a good agreement with the model. The proposed pad model should be useful for the topography simulation, and it also guides the development of new polishing pads.

A novel surgical material made from collagen with high mechanical strength: a collagen sandwich membrane.

We have developed a novel collagen membrane with excellent mechanical properties using a new method and examined its breaking strength, microstructure, and absorption behavior in vivo. Types I and III atelopeptide collagen extracted from porcine skin by treatment with pepsin were used. One volume percent collagen hydrochloride solution, pH 3.0, was frozen in a cast, then freeze-dried and pressed. Both surfaces of the resulting membrane were coated with 2% w/v collagen hydrochloride solution, pH 3.0, and dried. This procedure was then repeated 10 times, and the membrane was finally heated in vacuo. Microstructural observation showed that the inner part of the membrane consisted of piles of thin collagen nonwoven fabric layers, whereas the coated surface consisted of an amorphous collagen layer. The breaking strength of this membrane with a thickness of 0.5 mm was 73.5 N/cm in dry conditions. The mechanical strength of the membrane was 3.4 to 10.8 times greater than that of control membranes that had not been subjected to coating procedures. The absorption of this membrane was investigated by an implantation test in rabbits. The absorption rate of the membrane in vivo was similar to that of the noncoated control material, and only minimal tissue reaction was evident. Because the mechanical properties of this membrane, made from only collagen, are adequate for suturing without reinforcement by other materials, and its absorption in vivo has so far been equal to that of collagen membranes, the membrane is potentially applicable for various surgical uses such as replacement of tissue defects.