Preparation of Janus Fabric by PVDF Electrospinning Technology and Its Unidirectional Water/Moisture Transportation Performance

Directional fluid transport is of significance to many physical processes in nature. How to manipulate this process by man-made material is still a key challenge to scientists. In this study, Janus fabric was constructed by electrospinning a layer of polyvinylidene fluoride (PVDF) nanofibers on woven cotton or gauze. The chemical composition, morphology and surface wettability of two sides of Janus fabric were characterized by infrared spectroscopy, scanning electron microscope (SEM) and contact angle measurement. By controlling the PVDF electrospinning time, the maximum hydrostatic pressure of Janus fabric with different PVDF thickness was measured. It was found that PVDF/gauze is more favorable for unidirectional water transportation, and the moisture also can transfer from hydrophobic side to hydrophilic side. With the advantages of facile preparation, low-cost and one-way water/moisture transportation, the Janus fabric prepared in this study can be applied for water separation, humidity transfer and water collection from the air.

Trilayered Fibrous Dressing with Wettability Gradient for Spontaneous and Directional Transport of Massive Exudate and Wound Healing Promotion

Excessive exudate at wound sites increases treatment difficulty and severely decelerates the healing process.In wound exu-date management,dressings with unidirectional liquid transport capability have exhibited enormous potential.However,it remains challenging to improve the one-way liquid transport efficiency.Herein,a trilayered fibrous dressing is constructed by sequentially electrospinning polyurethane(PU)and polyvinylidene fluoride(PVDF)onto cotton fabric.Through hot pressing,a stable wettability gradient is formed across the PVDF/PU/cotton dressing due to the melting and bridging of PU nanofib-ers.The trilayered dressing exhibited rapid unidirectional transport with water penetrating from the hydrophobic side to the hydrophilic side in 6 s.The hydrostatic pressure from the hydrophilic side to the hydrophobic side is 569%higher than that from the hydrophobic side to the hydrophilic side,indicating that the dressing has a profound unidirectional conductivity.In vivo experiments demonstrates that the trilayered dressing can accelerate the wound healing process,especially in the early stages of wound occurrence,by quickly draining the excessive exudate.This study provides a new method to construct wound dressings with wettability gradients,which are advantageous for efficient exudate removal.

Flexible,anti-damage,and non-contact sensing electronic skin implanted with MWCNT to block public pathogens contact infection

If a person comes into contact with pathogens on public facilities,there is a threat of contact(skin/wound)infections.More urgently,there are also reports about COVID-19 coronavirus contact infection,which once again reminds that contact infection is a very easily overlooked disease exposure route.Herein,we propose an innovative implantation strategy to fabricate a multi-walled carbon nanotube/polyvinyl alcohol(MWCNT/PVA,MCP)interpenetrating interface to achieve flexibility,anti-damage,and non-contact sensing electronic skin(E-skin).Interestingly,the MCP E-skin had a fascinating non-contact sensing function,which can respond to the finger approaching 0−20 mm through the spatial weak field.This non-contact sensing can be applied urgently to human–machine interactions in public facilities to block pathogen.The scratches of the fruit knife did not damage the MCP E-skin,and can resist chemical corrosion after hydrophobic treatment.In addition,the MCP E-skin was developed to real-time monitor the respiratory and cough for exercise detection and disease diagnosis.Notably,the MCP E-skin has great potential for emergency applications in times of infectious disease pandemics.

Dispersion of“guava-like”silica/polyacrylate nanocomposite particles in polyacrylate matrix

A series of“guava-like”silica/polyacrylate nanocomposite particles with close silica content and different grafting degrees were prepared via mini-emulsion polymerization using 3-(trimethoxysilyl)propyl methacrylate(TSPM)modified silica/acrylate dispersion.The silica/polyacrylate composite particles were melt-mixed with unfilled polyacrylate(PA)resin to prepare corresponding silica/polyacrylate molded composites and the dispersion mechanism of these silica particles from the“guava-like”composite particles into polyacrylate matrix was studied.It was calculated that about 110 silica particles were accumulated in the bulk of every silica/polyacrylate composite latex particle.Both the solubility tests of silica/polyacrylate composite latex particles in tetrahydrofuran(THF)and the section transmission electron microscope(TEM)micrographs of silica/polyacrylate molded composites indicated that the grafting degree of silica particles played a crucial role in the dispersion of silica/polyacrylate composite particles into the polyacrylate matrix.When the grafting degree of polyacrylate onto silica was in a moderate range(ca.20%-70%),almost all of silica particles in these“guava-like”composite particles were dispersed into the polyacrylate matrix in a primaryparticle-level.However,at a lower grafting degree,massive silica aggregations were found in molded composites because of the lack of steric protection.At a greater grafting degree(i.e.,200%),a cross-linked network was formed in the silica/polyacrylate composite particles,which prevented the dispersion of composite particles in THF and polyacrylate matrix as primary particles.

Phenolic rigid organic filler/isotactic polypropylene composites.I.Preparation

A novel phenolic rigid organic filler(KT)was melt-mixed with an isotactic polypropylene(iPP)to prepare a series of PP/KT composites,with or without maleic anhydride grafted polypropylene(MAPP)as compatilizer.The evolution of filler morphology during melt-mixing and melt-pressure processes was monitored by scanning electron microscope(SEM)and polarized optical microscope(POM).The influences of shear force,pressure time,filler content and MAPP concentration on the final filler dispersion were studied.We found that this rigid organic filler readily melted and dispersed homogenously into the iPP matrix through a fission-fusion process during the melt-mixing process.Thus a balanced dispersion,which was closely related to shear force and MAPP concentration,can be achieved.During the meltpressure process,parts of the filler particles combined gradually through a coalescence process.However,the incorporation of MAPP can effectively inhibit the tendency to coalesce and refine the filler particles sizes into nanoscale.Thus,a series of PP/KT composites with controllable filler particles size and narrow size distribution can be obtained just by adjusting process conditions and MAPP concentration.In addition,due to the in-situ formation mechanism,the filler phase possessed a typical solid true-spherical shape.

Phenolic rigid organic filler/isotactic polypropylene composites. Ⅱ. Tensile properties

A novel phenolic rigid organic filler(KT)was used to modify isotactic polypropylene(iPP).The influence of KT particles on the tensile properties of PP/KT micro-composites was studied by uniaxial tensile test and the mor-phological structures of the stretched specimens were observed by scanning electron microscopy(SEM)and polarized optical microscopy(POM).We found that the Young's modulus of PP/KT specimens increased with filler content,while the yield and break of the specimens are related to the filler particles size.The yield stress,the break-ing stress and the ultimate elongation of PP/KT specimens were close to those of unfilled iPP specimens when the max-imal filler particles size is less than a critical value,which is 7μm at a crosshead speed of 10 mm/min and 3μm at 200 mm/min,close to that of glass bead but far more than those of other rigid inorganic filler particles.The interfacial interaction was further estimated from yield stress,indi-cating that KT particles have a moderate interracial inter-action with iPP matrix.Thus,the incorporation of small KT particles can reinforce iPP matrix and simultaneously cause few detrimental effects on the other excellent tensile properties of iPP matrix,due to their organic nature,higher specific area,solid true-spherical shape and the homogen-ous dispersion of the ROF particles in microcomposites.

Phenolic rigid organic filler/isotactic polypropylene composites. Ⅲ. Impact resistance property

A novel phenolic rigid organic filler(KT)was used to modify isotactic polypropylene(iPP).The influence of KT particles on the impact resistance property of PP/KT specimens(with similar interparticles distance,1.8μm)was studied by notched izod impact tests.It was found that the brittle-ductile transition(BDT)of the PP/KT microcomposites took place at the filler content of about 4%,and the impact strength attains the maximum at 5%(with filler particles size of 1.5μm),which is about 2.5 times that of unfilled iPP specimens.The impact fracture morphology was investigated by scanning electron micro-scopy(SEM).For the PP/KT specimens and the high-density polyethylene/KT(HDPE/KT)specimens in ductile fracture mode,many microfibers could be found on the whole impact fracture surface.It was the filler particles that induced the plastic deformation of interparticles ligament and hence improved the capability of iPP matrix on absorbing impact energy dramatically.The determinants on the BDT were further discussed on the basis of stress concentration and debonding resistance.It can be con-cluded that aside from the interparticle distance,the filler particles size also plays an important role in semicrystal-line polymer toughening.

Dispersion of a novel phenolic rigid organic filler in isotactic polypropylene matrix by solution-mixing and melt-mixing

A novel phenolic rigid organic filler （named KD） with a high melting point was dispersed in an isotactic polypropylene （iPP） matrix by solution-mixing and/or melt-mixing. A series of KD/iPP blends was prepared with or without addition of maleic anhydride-grafted polypro- pylene （MAPP） as a compatibilizer. Influences of MAPP and mixing methods on the filler dispersion were studied using polaried optical microscope （POM）, scanning electron microscope （SEM） and tensile test. The filler particles are always inclined to form large irregular aggregates in the iPP matrix due to their significant differences in polarity and solubility in solvent. However, an iPP/MAPP/KD （PMK） blend containing filler particles with a quasi-spherical shape （-97.8 nm in diameter） and narrow particle size distribution （polydispersity index = 1.076） was successfully prepared by incorporating MAPP to reduce the interfacial tension and surface free energy between the dispersion phase and the continuous phase, and adopting a spray-drying method after solution-mixing to suppress the increase of the size of the dispersed phase during the removal of solvent.