High Effective Sensitivity, Wide Working Range of Melt-blown Nonwoven Conductive Substrates for Smart Wearable Strain Sensors

High sensitivity, wide working range and flexible portability of strain sensors are crucial for smart wearable applications. To obtain these performances, several elastic melt-blown nonwoven substrates with excellent flexibility and high conductivity were developed by loading with polypyrrole through a double-dipping and double-rolling finishing method. The structure and conductivity are characterized by scanning electron microscope, infrared spectrometer, digital source meter and so on. The results indicate that the conductivity of prepared substrates is affected by the pyrrole concentration and polypyrrole amount deposited in nonwovens. Obviously, the conductivity and sensitivity of substrates as strain sensors are highly and positively correlated to the fiber orientation in nonwovens, and the effective working range and corresponding sensitivity of sensors are determined by the elastic deformation interval of melt-blown substrate. When the pyrrole concentration is 5.5%, the nonwoven substrate with 45.30% porosity possesses the anisotropic optimal conductivity with 23.491 S m-1 along winding direction and 15.063 S m-1 along width direction. Moreover, the as-prepared flexible conductive substrate exhibits the characteristics of wide working strain range (0-24.2%), high sensitivity with 1.94 gauge factor at the range, fast response (0.023 s), tiny hysteresis (0.011s), high durability and stability after 1000 cycles. Furthermore, the as-prepared sensor provides an effective method to prepare smart wearable strain sensors used as the monitor of finger bending in details and the precise recognition of human voice changes.

Elastic melt-blown nonwoven fabrication of styrene‐ethylene/butylene‐styrene copolymer and polypropylene blends: a study of morphology and properties

Fabrics produced by the melt-blown nonwoven process have the advantage over competing materials of possessing an ultrafine fibrous and porous structure. However, their brittleness and poor toughness restrict their wider application. There is increasing demand for nonwovens that have high stretchability and elasticity while maintaining a melt-blown structure. In this study, polypropylene (PP) and styrene‐ethylene/butylene‐styrene copolymer (SEBS) were blended at different ratios and subsequently used in the melt-blowing process. The morphology of the blends displayed a co-continuous structure when the ratio of SEBS to PP in blends was similar. Furthermore, it was found that all the blends had good spinnability from the melt-blowing process during rheological and thermal properties tests. All the elastic melt-blown nonwovens fabricated in this research had elongations higher than 400% and elastic recoveries higher than 50%, which was indicative of good elasticity. Meanwhile, the nonwovens maintained fine fiber diameters and good filtration properties, in keeping with traditional melt-blown nonwovens.

Preparation of Ag@ZIF-8@PP Melt-Blown Nonwoven Fabrics: Air Filter Efficacy and Antibacterial Effect

Serving as matrices, polypropylene (PP) melt-blown nonwoven fabrics with 4% electrostatic electret masterbatch were incorporated with a 6%, 10%, 14%, or 18% phosphorus-nitrogen flame retardant. The test results indicate that the incorporation of the 6% flame retardant prevented PP melt-blown nonwoven fabrics from generating a molten drop, which, in turn, hampers the secondary flame source while increasing the fiber diameter ratio. With a combination of 4% electrostatic electret masterbatch and the 6% flame retardant, PP melt-blown nonwoven fabrics were grafted with ZIF-8 and Ag@ZIF-8. The antibacterial effect of ZIF-8 and Ag@ZIF-8 was 40% and 85%, respectively. Moreover, four reinforcing measures were used to provide Ag@ZIF-8 PP melt-blown nonwoven fabrics with synergistic effects, involving lamination, electrostatic electret, and Ag@ZIF-8 grafting, as well as a larger diameter because of the addition of phosphorus-nitrogen flame retardants. As specified in the GB2626-2019 and JIS T8151-2018 respiratory resistance test standards, with a constant 60 Pa, Ag@ZIF-8 PP melt-blown nonwoven membranes were tested for a filter effect against PM 0.3. When the number of lamination layers was five, the filter effect was 88 ± 2.2%, and the respiratory resistance was 51 ± 3.6 Pa.

Preparation and Characterization of magnetic PLA/Fe3O4-g-PLLA composite melt blown nonwoven fabric for air filtration

A kind of magnetic poly (lactic acid) (PLA) melt blown nonwoven fabric (MB) was fabricated by the introduction of ferroferric oxide (Fe3O4) nanoparticles to improve its air filtration performances. In view of the poor compatibility of two components, the poly (L-lactic acid) (PLLA) molecular chains was firstly grafted onto the Fe3O4 nanoparticles surface via the ring opening polymerization (ROP). Then, PLA/Fe3O4-g-PLLA composite masterbatches with different mass ratios were prepared by melt-blending method and processed into the corresponding composite MB. The structures and performances of PLA/Fe3O4-g-PLLA composite masterbatches and their MB were investigated. The results showed that the addition of Fe3O4-g-PLLA nanohybrids hardly influenced the glass transition, cold crystallization and melting behaviors of the composite masterbatches. Though the melt fluidity of the composite masterbatches reduced with the Fe3O4-g-PLLA content increasing, the composite masterbatches still could present the appropriate processability in the range of 210°C to 230°C. Fe3O4-g-PLLA could be uniformly dispersed in PLA matrix and had a good interfacial compatibility with the matrix. Compared with pure PLA MB, the fiber surface of the composite MB became slightly rough, the pore size and distribution of the fiber web increased. The addition of Fe3O4-g-PLLA endowed PLA MB with magnetism. With the increasing of Fe3O4-g-PLLA content, the air permeability of the composite MB was improved and their filtration resistance obviously reduced. When the content of Fe3O4-g-PLLA was 0.5 wt%, the filtration efficiency of the composite MB reached the maximum. Moreover, the composite MB have higher longitudinal tensile strength and elongation at break than those of pure PLA MB.

Effect of microfiber layers on acoustical absorptive properties of nonwoven fabrics

There are several types of sound absorptive materials, such as natural and synthetic fibers, acoustic mineral wool, acoustic polyester panels, acoustic foam, cotton batts, that reduce the acoustic energy of a sound wave as the wave passes through. In this work, the use of nonwoven materials made of cotton, polyester, and polypropylene fibers for the development of sound absorptive nonwoven materials has been investigated. Samples of different materials (cotton, cotton/polyester blend, polyester fibers needle punched, and polypropylene melt blown nonwoven) and multilayer structures were tested on the designed impedance tube. Acoustic absorption properties of the fiber assemblies were studied in the frequency region of 100–1500 Hz. The values of sound absorption coefficient for different samples indicated that polypropylene microfiber melt blown nonwoven sample displayed a good sound absorption behavior in the entire frequency range. The use of multilayer samples improves the sound absorption coefficient with the condition that one of the layers is a thin melt blown nonwoven layer. The formation of nonwoven absorbent material consisted of hybrid layers, significantly reduces the resultant average sound absorption coefficient, especially when the upper layer is made from finer fibers of melt blown nonwoven of low air permeability value, and in this case the improvement reaches 50%. The use of melt blown layers of fine fibers values of noise reduction coefficient may reach 0.8. The multilayer nonwoven sound absorber design should take into consideration specific noise reduction coefficient values, not the absolute ones, particularly when the weight of the absorber is playing a decisive role.

Hydrophilic and antimicrobial properties of acrylic acid and chitosan bigrafted polypropylene melt-blown nonwoven membrane immobilized with silver nanoparticles

The polypropylene melt-blown nonwoven membrane (PPM) is widely used in healthcare; however, the highly hydrophobic nature of the PPM readily adsorbs proteins and polysaccharides, which are conducive to bacteria being retained in the network, resulting in biofouling. Therefore, to improve the hydrophilic and antimicrobial properties of PPM, acrylic acid (AA) was first graft-polymerized on PPM (PPM- g-AA) by ultraviolet (UV)-induced photo-grafting polymerization. Chitosan (CS) was then covalently grafted onto PPM- g-AA to obtain the bigrafted PPM (PPM- g-AA- g-CS). Finally, silver (Ag) nanoparticles were immobilized onto PPM- g-AA- g-CS to create the hydrophilic and antibacterial PPM. The surface chemical composition and morphology of the samples were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The hydrophilic and antimicrobial properties of the modified PPM were assessed using static water contact angle measurements, wetting time, and bacteria colony-counting assays. The results show that PPM- g-AA- g-CS with immobilized Ag nanoparticles has excellent antibacterial and hydrophilic properties.