Good Breathability Research Articles

Self-roughened omniphobic coatings on nanofibrous membrane for membrane distillation

Novel omniphobic electrospun nanofibrous membranes (ENMs) for direct contact membrane distillation (DCMD) were fabricated by electrospinning poly(vinylidene fluoride) (PVDF) nanofibers and followed by directly functionalizing the fiber surface with long-chained fluorododecyltrichlorosilane (FTCS) via solution immersion without any assistance of roughening treatments. The morphologies of polymerized fluorododecyltrichlorosilane (PFTCS) coated PVDF nanofibers evolved from the newly budding willow twigs with tiny bumps, to vigorous buds and then to intertwined fillets with the increase of FTCS concentration, which could serve as a robust barrier to low-surface-tension liquid penetration. By constructing hierarchically re-entrant structures of low-surface-energy PFTCS coating layer onto the PVDF nanofibers, the resultant porous ENMs were endowed with omniphobic property, low water-adhesion property, remarkable mechanical property, and superior durability in harsh circumstances as well as good breathability. The comprehensive investigations on structural attributes (such as the liquid entry pressure, pore size, porosity and gas permeability), long-term MD stability and DCMD performance in presence of surfactants were carried out. Significantly, the resultant omniphobic PFTCS/PVDF membrane exhibited a competitive permeate vapor flux of 36.9 kg/(m2 h) in highly salty solution (3.5 wt% NaCl salt feed; ΔT = 40 °C) over 24 h operation and also demonstrated robust DCMD performance in presence of surfactants. Compared with the commercial PVDF MD membranes, this simple and scalable strategy had great potential for MD applications.

A Compound Yarn Based Wearable Triboelectric Nanogenerator for Self‐Powered Wearable Electronics

AbstractWearable devices such as activity tracker, digital bracelet, and smartwatch become more and more popular. However, these devices need to be charged regularly due to the limited battery capacity. Therefore, it is important to develop a method to harvest mechanical energy from human motions to drive the wearable devices. Here, a wearable triboelectric nanogenerator (WTNG) based on compound yarns, which can be integrated well with clothing due to its good breathability and flexibility, is reported. The WTNG can be mass produced owing to the low cost and process maturity. Furthermore, the WTNG exhibits outstanding flexibility, breathability, and comfortability. The WTNG can generate a maximum short‐circuit current of 4 µA, delivering an instantaneous power density of 11.0 mW m−2 to an external load. Electronic devices such as digital watch and scientific calculator can be powered by a capacitor that is charged by WTNG. This work presents a significant step toward wearable electronics and will be a widely adopted technology in the near future.

A Thermally Insulating Textile Inspired by Polar Bear Hair.

Animals living in the extremely cold environment, such as polar bears, have shown amazing capability to keep warm, benefiting from their hollow hairs. Mimicking such a strategy in synthetic fibers would stimulate smart textiles for efficient personal thermal management, which plays an important role in preventing heat loss and improving efficiency in house warming energy consumption. Here, a "freeze-spinning" technique is used to realize continuous and large-scale fabrication of fibers with aligned porous structure, mimicking polar bear hairs, which is difficult to achieve by other methods. A textile woven with such biomimetic fibers shows an excellent thermal insulation property as well as good breathability and wearability. In addition to passively insulating heat loss, the textile can also function as a wearable heater, when doped with electroheating materials such as carbon nanotubes, to induce fast thermal response and uniform electroheating while maintaining its soft and porous nature for comfortable wearing.

Co-delivery of deferoxamine and hydroxysafflor yellow A to accelerate diabetic wound healing via enhanced angiogenesis

Nonhealing chronic wounds on foot induced by diabetes is a complicated pathologic process. They are mainly caused by impaired neovascularization, neuropathy, and excessive inflammation. A strategy, which can accelerate the vessel network formation as well as inhibit inflammatory response at the same time, makes it possible for effective diabetic ulcers treatment. Co-delivery of multiple drugs with complementary bioactivity offers a strategy to properly treat diabetic wound. We previously demonstrated that hydroxysafflor yellow A (HSYA) could accelerate diabetic wound healing through promoting angiogenesis and reducing inflammatory response. In order to further enhance blood vessel formation, a pro-angiogenic molecular called deferoxamine (DFO) was topically co-administrated with HSYA. The in vitro results showed that the combination of DFO and HSYA exerted synergistic effect on enhancing angiogenesis by upregulation of hypoxia inducible factor-1 alpha (HIF-1α) expression. The interpenetrating polymer networks hydrogels, characterized by good breathability and water absorption, were designed for co-loading of DFO and HSYA aiming to recruit angiogenesis relative cells and upgrade wound healing in vivo. Both DFO and HSYA in hydrogel have achieved sustained release. The in vivo studies indicated that HSYA/DFO hydrogel could accelerate diabetic wound healing. With a high expression of Hif-1α which is similar to that of normal tissue. The noninvasive US/PA imaging revealed that the wound could be recovered completely with abundant blood perfusion in dermis after given HSYA/DFO hydrogel for 28 days. In conclusion, combination of pro-angiogenic small molecule DFO and HSYA in hydrogel provides a promising strategy to productively promote diabetic wound healing as well as better the repair quality.

Utilization of Tannins Extract of Acacia seyal Bark (Taleh) in Tannage of Leather

Leather is a durable and flexible material created by the tanning of animal raw hide and skin, primarily cattle hide and natural grain, variation in the grains, good breathability and other natural features are all signs that the material is genuine. The most commonly used tanning methods are chrome and vegetable tanning. The vegetable tannins are extracted by using a suitable solvent, usually water followed by concentration and spray drying to get powder or solid. The tanneries in the Sudan imported mimosa and synthetic (syntan) tannins material for the process of retanning and pretanning. This study was undertaken to utilize Taleh bark (Acacia seyal Bark) as a retanning material for production of upper and garment leathers. The tannins content of Taleh bark was found to be 28.9% and therefore it was promising and would successfully be used as retaining and tanning materials. In this study; the factors that affect leaching which are mainly time, solvent to solid ratio, temperature, agitator speed and time of extraction. A two - level factorial experiments were designed and the level of the above factors was determined according to the statistical analysis. It was found that a solvent solid ratio of 6:1, speed of agitation of 250 rpm, temperature of 30°C and time 2 hours were the optimum conditions. A complete design of a long tube triple-effect evaporator is made for production of 1000 tons per year which is enough for the present level of capacities in the tanneries to date. In conclusion it is clear that Sudan can produce tannins extract from Taleh bark which can be used for pretannage, tannage and retannage. It is recommended that the Taleh bark and similar Acacia seyal can be analyzed and leached to give tannins powder extract to replace imported Mimosa extract.

Tailoring Water-Resistant and Breathable Performance of Polyacrylonitrile Nanofibrous Membranes Modified by Polydimethylsiloxane.

The demand of water-resistant and breathable materials applied to a separation medium and protective garments is steadily increasing. Typical approaches to obtain these functional materials are based on hydrophobic agents and porous substrates with small fiber diameter, tiny pore, and high porosity. However, a fluorinated hydrophobic finishing agent usually employed in providing effective waterproofness is limited with respect to their environmental persistence and toxic potential. Herein, with the aim to keep a balance between the water-resistance and breathability as well as mechanical properties, we fabricate a novel fluoride-free functional membrane by electrospun polyacrylonitrile (PAN) nanofibers modified with polydimethylsiloxane (PDMS). As determined by morphological, DSC, and FT-IR analyses, the curing reaction of PDMS macromolecules formed an abundance of hydrophobic adhesive structures, which improved the waterproof performance dramatically and imparted relative good breathability at the same time. By systematically tuning the curing temperature as well as the concentration of PDMS, the modified PAN membranes with 4 wt % PDMS possessed good water-resistance (80.9 kPa), modest vapor permeability (12.5 kg m-2 d-1), and air permeability (9.9 mm s-1). Compared with pristine PAN membranes, the modified membranes were endowed with enhanced tensile stress of 15.7 MPa. The good comprehensive performance of the as-prepared membranes suggested their potential applications in protective clothing, membrane distillation, self-cleaning materials, and other medical products. Furthermore, the proposed relationship between porous structure and waterproof/breathable property as one considerable principle is applicable to designing functional membranes with different levels of protective and comfortable performance.

Metakaolin as a precursor of materials for applications in Cultural Heritage: Geopolymer-based mortars with ornamental stone aggregates

Potentialities and suitability of metakaolin-based geopolymers in Cultural Heritage have been explored. In particular, in order to evaluate their possible use as restoration materials in conservation of historic manufactures, mortars have been prepared by adding aggregates of Italian ornamental stones to alkali-activated metakaolin with binder/sand ratio of 1:1. To improve workability, geopolymer binders have been synthesized from metakaolin and sodium silicate solution with water/solid weight ratios between 0.33 and 0.66 and SiO2/Al2O3 and Al2O3/Na2O molar ratios of 3.70 and 1.04, respectively, and characterized by several techniques, including mechanical strength tests according to UNI EN 196-1. All binders display good mechanical properties, with compressive and flexural strength values as high as 72MPa and 6MPa, respectively, and decreasing with increasing water/solid ratio. The increase of water in geopolymer formulation has little negative effect on the aluminosilicate gel development and on the strength of these materials.Mortars display a homogeneous and compact matrix, bonded (silicoaluminate aggregates) or interlocked (carbonate) with aggregates. Their compressive strengths fall in the masonry mortars class M20 range. Their pore size distribution guarantees good breathability and adaptability to the substrate. The final materials mimic the original stones, with good aesthetic compatibility.

Tough and porous piezoelectric P(VDF-TrFE)/organosilicate composite membrane

Novel P(VDF-TrFE)/organosilicate composite membrane was fabricated by electrospinning. The electrospun composite membrane containing as little as 2 wt% of organosilicate demonstrated significant improvements in strength, modulus, and toughness by about 103%, 45%, and 97%, respectively, when compared with those of electrospun pure P(VDF-TrFE) membrane, while maintaining high porosity and good breathability and piezoelectricity. We believe that such an organosilicate-reinforced durable, porous, and piezoelectric P(VDF-TrFE) membrane has huge advantages in various applications such as flexible sensors, wearable electronics, filter membrane, tissue engineering, battery separator, and polymer electrolyte.

Carbon Nanotubes Enhanced Fluorinated Polyurethane Macroporous Membranes for Waterproof and Breathable Application.

Waterproof and breathable macroporous membranes that are both completely resistant to liquid water penetration and easily allowable to vapor transmission would have significant implication for numerous applications; however, fabrication of such materials has proven to be tremendously challenging. Herein, we reported novel electrospun composite fibrous membranes with high waterproof and breathable performance, which consisted of polyurethane (PU), terminal fluorinated polyurethane (FPU), and carbon nanotubes (CNTs). Benefiting from the utilization of FPU and CNTs, the fibrous membranes were endowed with superhydrophobic surface, optimized pores size and porosity, along with enhanced fibers, which resulted in excellent waterproof, breathable and mechanical properties. Significantly, the relationship among waterproofness, pore structure and surface wettability has been confirmed finely accordance with Young-Laplace equation. Ultimately, the resultant membranes presented high waterproofness with hydrostatic pressure up to 108 kPa, good breathability with water vapor transmission rate over 9.2 kg m(-2) d(-1), as well as robust mechanical properties with bursting strength of 47.6 kPa and tensile strength of 12.5 MPa, suggesting them as promising alternatives for a number of potential applications, such as protective clothing.

Study of Performance Characteristics of Fabrics Coated with PVC based Formulations

The cotton base fabric with plain weave was coated with different coating formulations for exploring the best possible formulation for achieving reasonably good waterproofing and breathability. The coated fabrics were manufactured with Polyvinyl Chloride (PVC) resin, mixture of PVC and Polyurethane (PU) and PVC mixed with Polyethylene Glycol (PEG)/Ethylene Glycol (EG) additives. The properties of coated fabric were studied for two solutions of coagulation bath. The characteristics of coating film were studied by subjecting the coated fabric samples to water treatment. The film porosity was found to be high for all cases, corresponding to low rate of coagulation. Also it was observed that on washing the porosity of film was increased. The fabric coated with mixture of PVC and PU formulation found to give best breathability (around 60 to 75% of control fabric) with water penetration resistance exceeding 150 cm head of water.

Design of Polymeric Nanofiber Gauze Mask to Prevent Inhaling PM2.5 Particles from Haze Pollution

Recently, PM2.5 (particulate matter with diameter of 2.5 micron or less) has become a major health hazard from the polluted air in many cities in China. The regular gauze masks are used to prevent inhaling the PM2.5 fine particles; however, those masks are not able to filter out the PM2.5 because of the large porosity of the mask materials. Some well-prevented masks usually have poor breathability, which increases other health risks. In this study, a polysulfone based nanofiber for mask filtration material was synthesized by electrospinning. That nanofiber mask material was characterized by SEM, air permeability test, and PM2.5 trapping experiment. The results indicate that nanofiber mask material can efficiently filter out the PM2.5 particles and simultaneously preserve a good breathability. We attribute such improvement to the nanoscaled fibers, having the same porosity as that of regular gauze mask but with extremely reduced local interfiber space.

Protective Clothing Using Nanofibers

Currently many different types of protective garments are used designed to protect the wearer against biological contamination (e.g., bacteria) and mechanical impurities (such as dust, drops of technical fluids, etc.). Their disadvantage is that, thanks to the materials used in the requirement of a high level of protection for the user, a very low permeability even to zero, so that for example, do not allow to remove moisture and heat from the user's body and thus their use is quite uncomfortable, and conversely, in case of the requirement of good breathability and high comfort of application have very little effectiveness in detecting biological and mechanical impurities, which is not sufficient for a number of disciplines.