The Nonwovens Institute

Adhesive biodegradable membranes (patches) for the protection of pruning locations of plants from esca fungi attacks were developed using electrospun soy protein/polyvinyl alcohol and soy protein/polycaprolactone nanofibers. Several different water-soluble adhesives were either added directly to the electrospinning solutions or electrosprayed onto the as-spun nanofiber mats. The nanofibers were deposited onto a biodegradable rayon membrane, and are to be pressed onto the pruned location on a plant. The pore size in the nanofiber mats is sufficient for physically blocking fungi penetration, while the outside rayon membrane provides sufficient mechanical support in handling prior to deposition on a plant. Diseases like Vine Decline are one of the most important cases where such a remedy would be needed. It should be emphasized that these novel biodegradable and sticky patches are radically different from the ordinary electrospun ultra-filtration membranes. The normal and shear specific adhesive energy of the patches were measured, and the results show that they can withstand strong wind without being blown off. On the other hand, the patches possess sufficient porosity for plant breathing.

In this paper, a modeling study is presented to simulate the fluid infiltration in fibrous media. The Richards’ equation of two-phase flow in porous media is used here to model the fluid absorption in unsaturated/partially saturated fibrous thin sheets. The required consecutive equations, relative permeability, and capillary pressure as functions of medium’s saturation are obtained via fiber-level modeling and a long-column experiment, respectively. Our relative permeability calculations are based on solving the Stokes flow equations in partially saturated three-dimensional domains obtained by imaging the sheets’ microstructures. The Richards’ equation, together with the above consecutive correlations, is solved for fibrous media inclined with different angles. Simulation results are obtained for three different cases of upward, horizontal, and downward infiltrations. We also compared our numerical results with those of our long-column experiment and observed a good agreement. Moreover, we establish empirical coefficients for the semianalytical correlations previously proposed in the literature for the case of horizontal and downward infiltrations in thin fibrous sheets.

Abstract Modifications of polypropylene (PP) are often carried out to either functionalize them or meet specific property demands. This study considered the process of PP grafting with glycidyl methacrylate (GMA) as an intermediate step to achieve improvements in surface properties of this polymer. Abundant literature is available on this grafting process but little is known about the surface properties of the grafted PP. Present work considered both experimental and computational approaches to attain this goal. Experimentally, it was established that the melting temperature of modified PP changed with the addition of GMA, and at higher concentrations of GMA in the PP matrix, heterogeneous nucleation took place. Experimental results revealed a decrease in the surface energy (SE) as well. To discern the underlying reasons behind these changes, molecular dynamics simulations were undertaken. The computational results revealed that the changes in SE could be associated with the location of the functional group. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Hydroentangled nonwovens of raw white cotton fiber, scoured white cotton fiber, and raw brown cotton fiber are effective hosts for mineralization of calcium carbonate polymorphs to modify and improve their thermal and surface properties.

, surface tension, electrical conductivity…) and quantify their impact on fiber capture efficiency. It was found, in particular, that droplet's electrical conductivity and permittivity have the most adverse impact on the performance of an electret fiber. This is perhaps because higher droplet conductivity results in severe fiber charge neutralization, and higher droplet permittivity leads to a stronger fiber charge shielding. In contrast, fiber wettability was found to have a negligible impact on fiber efficiency. The work presented in this paper offers valuable insights into the complex nature of electret filters used in different industrial and environmental applications.

• Developed a new method to generate fibrous media from soft and flexible fibers. • Developed a CPU-friendly method to simulate permeability of bimodal fibrous media in 3-D. • Examined accuracy of analytical expressions for permeability calculation for bimodal media. • Cube Root Mean and Area Weighted mean diameters seem to be most accurate among all. In this study, we utilized a Discrete Element Model (DEM) approach to generate fibrous media comprised of flexible fibers with different diameters. This approach allowed simulations to predict the solid volume fraction (SVF) of the resulting media, which is a unique advantage over previous models reported in the literature, where SVF was used as an input to the fiber generation algorithms. We generated realistic bimodal fibrous media in which coarse and fine fibers of different mass ratios, SVFs, and coarse-to-fine fiber diameter ratios were intimately blended. Permeability of the resulting media were predicted by numerically solving the Stokes equations in the 3-D space between the fibers. To circumvent the need to conduct excessively expensive numerical simulations, we developed a Micro-Macro simulation approach in which the fine fibers were treated as porous matrix engulfing the coarse fibers. The accuracy of our CPU-efficient Micro-Macro simulations was assessed through comparison with the more accurate Micro-Micro (CPU-intensive) simulations, where the actual geometry of both the fine and coarse fibers were resolved. The Micro-Macro simulations were then used to produce a dataset of permeability values to be used in assessing the accuracy of different methods of defining an equivalent unimodal structure that can represent a bimodal fibrous medium for permeability calculation. Our study concluded that the cube-root and area-weighted mean diameter models provide the most accurate predictions for the permeability of bimodal fibrous media. Our theoretical results were compared with experimental data and reasonable agreement was observed.

While significant research efforts have focused on the negative and positive electrode materials in rechargeable Lithium-ion (Li-ion) batteries, battery separators have only recently received more consideration from the scientific community. The separator plays a critical role in Li-ion batteries by preventing physical contact between the positive and negative electrodes while permitting efficient ionic transport across the separator. There are four major types of separators: microporous polymeric membranes, nonwoven polymeric mats, gel-polymer electrolytes and composite membranes. Relative to the more conventional microporous membrane separators, nonwovens have the advantage of low cost, low mass and high porosity; in addition, the fibrous mat provides good structural cohesion due to its intertwined fibers. Although most polymers used to make nonwoven battery separators have resulted in lower cell performance (lower ionic conductivity and higher resistance) than conventional microporous separators, polyvinylidene difluoride (PVDF) shows promising results because of its stability and affinity for electrolytes commonly employed in Li-ion cells. The best manner to produce nonwoven PVDF would employ a melt-blowing process, which is a well-developed, high-volume production technology. To be melt-blowable, polymer resins must have high melt-flow rates but commercial PVDF resins did not possess this property until recently. Nevertheless, researchers have successfully electrospun PVDF from a solution with the goal of exploring this promising polymer as a nonwoven battery separator. We are investigating the fundamental properties and characteristics of two novel melt-blowable PVDF grades (Kynar ® 705 and Kynar ® ADS II from Arkema) with the objective of elucidating their structure-property-process relationships and studying their performance as separators in Li-ion batteries. In this work, we will report on the physical, chemical, and electrochemical properties of nonwoven PVDF relevant to their use as battery separators.

Two modeling techniques are introduced to predict the sheet resistance of electrically conductive continuous filament nonwoven fabric: a two-dimensional (2–D) discrete filament stochastic resistor network simulation, and a simple analysis using a laminate analogy. The effects of anisotropy and sample size are considered. Results are compared with experiments on a silver coated point bonded nylon nonwoven fabric. For this particular sample, experimental sheet resistance results are significantly under-predicted by the 2–D analytical and simulation approaches where perfect inter-filament bonding is assumed. The utility of the 2–D perfect bonding predictions as an ultimate lower bound on the sheet resistance that may be achieved by extremely well-bonded continuous filament networks is discussed. Simulations of 2–D filament webs with poor inter-filament bonding and moderate anisotropy are shown to agree well with the present experiments. Taken together, the present results suggest that modeling of the in-plane conduction behavior of a general continuous filament nonwoven fabric requires a 3–D structural approach to capture the effect of an appropriate number density of inter-filaments bonds.

Nanofibers, measuring 500 nm or less, can be produced via different methods, such as electrospinning, meltblowing, or using "splittable" or "soluble" bicomponent fibers. Filaments made by meltblowing or electrospinning have lower strength and higher variability in the fiber diameters than fibers produced via the segmented pie or islands-in-the-sea technique. Webs made of electrospun or meltblown fibers should be laid over a suitable substrate that has to provide appropriate mechanical properties and complementary functionality to the web. Meltblowing produces microfibers rather than nanofibers, moreover it can process only limited number of polymers. Electrospinning, on the other hand, is able to make nanowebs with substantially more and smaller micropores than meltblown or spunbonded web; however, it has very low productivity. The segmented pie and islands-in-the-sea fibers produce highly developed and strong ultrafine nanofibers. However, despite a lot of similarities between these techniques, the I/S method has less limitations on the polymer choice and more options for the fiber cross sections, and it allows to produce smaller fibers than the segmented pie approach. Moreover, the islands-in-the-sea fibers are less challengeable to spin than the wedge pie fibers, especially when appropriate spin-pack design is chosen. Based on all abovementioned, the I/S approach, which involves spinning of the bicomponent fibers via the spunbonding process and fibrillating them by hydroentanglement, remains a promising method for the production of nanofibers.

Among all types of Li-ion battery (LIB) separators, fibrous mats have the advantage of low cost, low mass, and high porosity. Fibrous Poly(Vinylidene difluoride) (PVDF) shows promising results because of its stability and affinity for electrolytes commonly employed in Li-ion cells. Despite numerous studies published on LIB separators, none reports structure-property relationships for the identification of an ideal structure. We investigated the properties of a melt-blowable PVDF and produced meltblown PVDF mats in scale-up equipment with the objective of elucidating its performance as a LIB separator. We also present a new class of LIB separators, PVDF-based highly-branched, colloidal polymer particulates called soft dendritic colloids that are produced by shear-driven polymer precipitation within a highly turbulent nonsolvent flow, followed by filtration. We show that the morphology of the resulting PVDF particulates can be modulated from fibrous soft dendritic colloids (SDC) to thin and highly porous sheet-like particles. Through a scale-up system, we obtained high-quality meltblown PVDF with high homogeneity, low number of defects, an average fiber diameter of 1.4 μm, and pore size as low as 0.9 μm. Small fiber diameter provides high-surface area and high-electrolyte uptake. We show interactions of the meltblown PVDF with the electrolyte lead to a morphology change in the fibers. The highest ionic conductivity was ~ 9.6 mS/cm, and the first-cycle capacity was 140 mAh/g (Li/LiCoO 2 ). After melt-pressing, the thickness and pore size decrease, but the mats electrolyte absorbency and conductivity decrease commensurately. PVDF SDC separators show high porosity (up to 80%) and high particle surface area, which results in high conductivity (1.2 mS/cm), high-electrolyte uptake (325%), and high-cell capacity (112 mAh/g in Li/LiCoO 2 cell) with <10% loss after 50 cycles. Both processes yield separators with low thermal shrinkage (<5% at 90 ºC) and high tensile strength (<0.5% offset at 1000 psi), with the highest-performing separator possessing low average fiber diameter with a wide diameter distribution. Both meltblowing and shear-driven precipitation are facile and versatile processes for high-volume fabrication of LIB separators with one single polymer without necessarily requiring post-processing and with characteristics similar to commercially available battery separators. Our findings show that battery separators should be fabricated with a low pore size (<2 µm) but also with a wide pore distribution. When the strength and openness of the micropores are coupled with a dense net of nanopores, an ideal Li-ion battery separator is obtained. References: Luiso, S., Henry, J. J., Pourdeyhimi, B. & Fedkiw, P. S. (2020). Fabrication and Characterization of Meltblown Poly(vinylidene difluoride) Membranes. ACS Appl. Polym. Mater. , 2, 2849–2857. S. Roh, A. H. Williams, R. S. Bang, S. D. Stoyanov, and O. D. Velev (2019). Soft dendritic microparticles with unusual adhesion and structuring properties. Nature Materials , vol. 18, no. 12. pp. 1315–1320.

Various collocation of new type cotton feeder is introduced in the paper.It is explained that new collocation method may satisfy different technics process.

Production process and machines of rubbing materials and polishing fabric are introduced in the paper.

Interfacial strength in bicomponent fibers remains a significant challenge jeopardizing durable adhesion and delamination prevention. An integrated experimental-numerical approach is developed here to engineer strengthened interfaces by means of compatibilizers and quantify their effect. Measurements of interfacial adhesion energy indicate that chemically dissimilar polyamide/polyolefin pairs reveal substantially lower values than those of polypropylene/polyethylene (PP/PE). In the case of PP/PE interfaces, compatibilizers markedly increase the adhesion energy while leaving bulk mechanical properties essentially unaffected. Numerical analysis identified that the area ratio and the mismatch in the thermal expansion are the dominant factors determining the interfacial stresses. Elucidation of additional material pairs and geometries reveals results ranging from stable compressive interfaces to disjoining high-stress regions that promote interfacial delamination. Overall, the results support the applicability of the present approach to provide quantitative guidance for designing bicomponent fibers toward either durable interfaces or delaminated interfaces by design.