Highly porous polyacrylonitrile/polystyrene nanofibers by electrospinning

The concept of phase separation was coupled with electrospinning to induce polyacrylonitrile (PAN) and polystyrene (PS) bicomponent electrospun fibers that, upon removal of the phase-separated PS domains by solvent extraction, became nanoporous. Electrospinning of PAN (Mw 150 kDa) with 5 % w/w PS (Mw 250 kDa) at a 10 % w/w total concentration in N,N-dimethylformamide (DMF) produced fibers with stable morphology and average diameters from 1130±680 to 890±340 nm by FESEM. The nanoporous fibers made from a 95/5 w/w PAN/PS bicomponent precursor had internal pores of about 20∼110 nanometers. Pore sizes of the porous PAN fibers were decreased to approximately ∼25 nm after oxidation and carbonization thermal treatment because of fiber shrinkage during the thermal treatment. The fibers retained a high density of pores after the thermal treatment.     

Preparation and characterization of nanoscaled poly(vinyl alcohol) fibers via electrospinning

Nanoscaled PVA fibers were prepared by electrospinning. This paper described the electrospinning process, the processing conditions, fiber morphology, and some potential applications of the PVA nano-fibers. PVA fibers with various diameters (50–250 nm) were obtained by changing solution concentration, voltage and tip to collector distance (TCD). The major factor was the concentration of PVA solution which affected the fiber diameter evidently. Increasing the concentration, the fiber diameter was increased, and the amount of beads was reduced even to 0%. The fibers were found be efficiently crosslinked by glyoxal during the curing process. Phosphoric acid was used as a catalyst activator to reduce strength losses during crosslinking. Scanning electron micrograph (SEM) and differential scanning calorimetric (DSC) techniques were employed to characterize the morphology and crosslinking of PVA fibers. It was found that the primary factor which affected the crosslinking density was the content of chemical crosslinking agent.     

热作废弃纤维资源利用与发展研究

我国热作废弃纤维资源丰富,其开发利用具有巨大的生态和经济价值。本文阐述近年来热作废弃纤维的综合利用现状,主要涉及饲料、肥料、功能性食品开发、制浆造纸、绿色化学品、生物质燃料开发、纳米纤维素等多个领域。对我国热作废弃纤维的资源化利用过程中存在的问题进行分析和讨论,并对其发展前景进行展望。     

Characterization and analysis of ligno-cellulosic seed fiber from Pergularia Daemia plant for textile applications

A hitherto uninvestigated ligno-cellulosic seed fiber from the plant Pergularia Daemia has been chosen for the current study to unravel its physical properties, and potentialities in textile applications. The raw, NaOH treated, and wax removed fibers were tested for their morphological and structural features by X-ray diffraction, SEM, FT-IR spectra, and thermal analysis by thermogravimetry and differential scanning calorimetry. The raw fibers have low cellulose content and less crystalline compared to cotton and are having hollow, smooth surface, and less density. The brittle nature and low elongation at break of virgin fiber makes it difficult for the spinning. It becomes spinnable after NaOH treatment due to the increased elongation at break by partial removal of lignin.     

Fabrication of Gelatin-Based Electrospun Composite Fibers for Anti-Bacterial Properties and Protein Adsorption

A major goal of biomimetics is the development of chemical compositions and structures that simulate the extracellular matrix. In this study, gelatin-based electrospun composite fibrous membranes were prepared by electrospinning to generate bone scaffold materials. The gelatin-based multicomponent composite fibers were fabricated using co-electrospinning, and the composite fibers of chitosan (CS), gelatin (Gel), hydroxyapatite (HA), and graphene oxide (GO) were successfully fabricated for multi-function characteristics of biomimetic scaffolds. The effect of component concentration on composite fiber morphology, antibacterial properties, and protein adsorption were investigated. Composite fibers exhibited effective antibacterial activity against Staphylococcus aureus and Escherichia coli. The study observed that the composite fibers have higher adsorption capacities of bovine serum albumin (BSA) at pH 5.32–6.00 than at pH 3.90–4.50 or 7.35. The protein adsorption on the surface of the composite fiber increased as the initial BSA concentration increased. The surface of the composite reached adsorption equilibrium at 20 min. These results have specific applications for the development of bone scaffold materials, and broad implications in the field of tissue engineering.     

木薯废弃物代替草炭减量在红掌盆栽基质上的研究应用

以红掌为试验材料，研究木薯废弃物加工生产的熟料基质替代草炭减量作为无土盆栽基质的可行性，结果表明：用木薯废弃物加工生产的熟料介质替代草炭，降低草炭含量的基质配方同样可以获得良好的栽培效果。初步筛选出适宜红掌生长开花的木薯废弃物加工生产的熟料基质优化组合体积配比为熟料介质40%＋草炭60%。用该熟料介质替代草炭，使得草炭减量的红掌无土盆栽基质是可行的。     

Production and characterization of fibroin hydrogel using waste silk fibers

The use of natural resources, especially processing wastes, as low cost and environmentally friendly alternative aiming high value-added applications is a subject of broad interest. Since the Brazilian silk production annually generates a large amount of waste during the silk fibers processing, this work explores the preparation and characterization of silk fibroin hydrogels using spinning waste silk fibers from textile processing and the processed ones. Hydrogels were obtained directly by dialyzing silk fibroin solutions against frequent changes of water until the gelation point and then lyophilized and characterized in terms of their morphology, crystallinity, thermal resistance and secondary structure. X-ray diffraction analysis revealed the presence of β-sheet conformation related to sol-gel transition. FT-IR spectra indicated the coexistence of random coil (silk I) and β-sheet (silk II) structures, with predominance of β-sheet conformation for hydrogels from processed silk fibers. From thermogravimetric analysis the presence of β-sheet secondary conformation was demonstrated by a degradation peak around 292 °C for both hydrogels. Freeze-dried hydrogels presented sheet or leaf like morphology and no significant change was observed among the hydrogels from waste silk fibers and processed ones. These characteristics suggest that silk fibroin hydrogels prepared from spinning waste silk fibers and obtained directly by dialysis can be potential candidates for biomaterials application, such as drug delivery systems and for wound dressings.     

Application of the Gadidae Fish Processing Waste for Food Grade Gelatin Production

Waste from fish cutting (heads, swim bladders, fins, skin, and bones) is a high-value technological raw material for obtaining substances and products with a wide range of properties. The possibility of using waste from cutting fish of the Gadidae family: the Alaska pollock (Gadus chalcogrammus) and the Pacific cod (Gadus macrocephalus), processed in the coastal zone, is scientifically substantiated. In this work, a technology has been developed for processing accumulated waste from fish cutting in order to obtain fish gelatin, which is characterized by high protein content (more than 80.0%) and a full set of essential and nonessential amino acids. We studied the quality of fish gelatin obtained from wastes from cutting the fish of the Gadidae family. The possibility of using fish gelatin as a component of fish products is shown; the dose of its introduction into the fish products is substantiated. The data obtained made it possible to recommend the use of fish processing waste products as a gelling component and a source of amino acids in multicomponent food systems.     

Preparation,characterization of antibacterial PLA/TP nanofibers

Polylactic acid (PLA)/Tea polyphenol (TP) composite nanofilms were prepared using an electrospinning process. The mixed dichloromethane (DCM) and N,N-dinethylformamide (DMF) (70:30, v/v) was found to be the most suitable solvent for electrospinning. Various blends of PLA/TP solutions were formed. The morphology of the electrospun nano-scale fibers was investigated by scanning electron microscope (SEM), and the antibacterial performance was tested using shake flask method. The average diameter of the fibers is between 380 and 850 nm. It was found that the fiber diameter decreases as TP content increases, however the fibers may become brittle when the blend ratio of PLA and TP reached 50/50 (w/w). The antibacterial performance can be improved at the beginning when TP content increased. But it gradually gets impaired when TP content surpasses a certain value. The highest inhibitory rate against Escherichia coli and Staphylococcus aureus are 96.9 and 97.6 % respectively.     

Highly stable coated polyvinylpyrrolidone nanofibers prepared using modified coaxial electrospinning

Hydrophobic polyvinylpyrrolidone (PVP) nanofibers, which is intensely hygroscopic, has been successfully prepared to improve their moisture resistance using a modified coaxial electrospinning process. A stearic acid (SA) solution was exploited as the sheath fluid to coat the fibers. Scanning electron microscopy demonstrated that the SA-coated PVP nanofibers became increasingly small with a rise in the sheath-to-core flow rate ratio; continuing to increase the sheath flow rate beyond a cut-off point resulted in nanofibres with very complicated morphologies. Transmission electron microscope images showed that SA formed a thin layer on the PVP nanofibers, with SA nanoparticles present on the fiber surfaces when a sheath-to-core flow rate ratio of 0.2:0.8 was used. Attenuated total reflectance-Fourier transform infrared spectroscopy verified the coating of SA onto the PVP nanofibers, and also the formation of hydrogen bonds between the SA and PVP molecules. The SA-coated PVP nanofibers were found to have much enhanced moisture resistance over pure PVP fibers. Modified coaxial electrospinning hence comprises a novel and powerful strategy for nanocoating and surface modification of polymer nanofibers.     

Effect of polystyrene mixing on mechanical properties and structural changes in melt spinning

To increase the spinning speed of poly(trimethylene terephthalate) (PTT) fibers, polystyrene (PS) was selected as an additive polymer in the PTT matrix. Mixing of the immiscible PS with PTT led to an increase in spinning speed up to 5,500 m/min. PS was employed to improve the extensibility of the matrix PTT in the spinning process as it can prevent PTT molecular orientation. Experimental results show that the mixing of PS achieved this. The elongation at break of spun fibers increased with the amount of PS. PS addition prevented fiber orientation, especially amorphous orientation, and improved drawability, and as such, increased spinning speed up to 5,500 m/min.     

Comparison of two electrospinning processes in obtaining finer polymer nanofibers

Two different electrospinning processes (traditional single fluid one and a modified coaxial electrospinning with organic solvent as sheath fluid) are investigated in relation to their capability of producing thinner nanofibers. Both the modified coaxial electrospinning and single fluid electrospinning can produce thinner nanofibers with polyvinylpyrrolidone (PVP) as a polymer model and using a poor volatile solvent N, N-dimethylacetamide (DMAc) in different ways. However the traditional single fluid process was less effective compared to the modified coaxial process, as it suffered more from the limitation of polymer chain entanglement threshold for maintaining structural uniformity of nanofibers. Using DMAc as sheath fluid in the modified process facilitated formation of thinner nanofibers without sacrificing their quality. The mechanism should be that an appropriate DMAc surrounding to the core polymer jet helps to retain it in a fluid state to experience a longer time electrical drawing, with little adverse influence on the polymer chain entanglements. Nanofiber diameters could also be tailored in a linear manner using the modified coaxial process simply through manipulating the sheath solvent flow rates. The modified coaxial process described here extends the capability of electrospinning process and opens a new way to obtain thinner nanofibers with fine structural uniformity.     

Titanium dioxide nanofibers prepared by using electrospinning method

The synthesis of titanium dioxide nanofibers with 200–300 nm diameter was presented. The new inorganic-organic hybrid nanofibers were prepared by sol-gel processing and electrospinning technique using a viscous solution of titanium isopropoxide (TiP)/poly(vinyl acetate) (PVAc). Pure titanium dioxide nanofibers were obtained by high temperature calcination of the inorganic-organic composite fibers. SEM, FT-IR, and WAXD techniques were employed to characterize these nanofibers. The titanium dioxide nanostructured fibers have rougher surface and smaller diameter compare with PVAc/TiP composite nanofibers. The anatase to rutile phase transformation occurred when the calcination temperature was increased from 600 °C to 1000 °C.     

Uniaxially well-aligned nanofiber arrays fabricated by electrospinning with a stable and low moving velocity jet

Aligned fibers in micro-/nano-scale have attracted more attention especially in tissue engineering field because cells can orientation growth along the fiber. However, it is still a huge technological challenge in achieving it as a result of the inherent bending instability of an electrospinning jet. Herein, we report a novel and simple spinning approach, in which low dielectric constant of dioxane was judiciously used as solvent for spinning dope, to obtain electrospinning jet with low induced charge, therefore eliminating electrically and aerodynamically driven bending instability, and forming a stable and low forward-moving velocity jet longer than 100 cm. This consequently allows for readily collecting and fabricating individual fibers, well-aligned ultrafine fiber arrays over large areas. Our approach has proved to be effective in preparing well-aligned ultrafine fibers from biodegradable poly(D, L-lactic acid) with different molecular mass, natural polymer acetyl cellulose and synthesized non-biodegradable polymer polystyrene.     

Alternative cleaning of compost leachate using biopolymer chitosan

Compost leachate poses a threat to the environment because it contains many organic and inorganic pollutants. Chemical Oxygen Demand (COD) has been reported at values above 5000 mg/l O₂. Heavy metals, such as nickel, lead, chromium are also present within these waters. Thus, in order to comply with the increasingly stringent environmental quality standards such contaminants must be removed effectively. The research approach in this paper is directed towards chelating pre-treatment procedures. Nontoxic and biodegradable biopolymer chitosan was used as a chelator for the removal of dissolved metals from compost leachate. The influence of chemical conditions regarding the chelation efficiency was studied in model solutions. The optimal treatment conditions were applied onto compost leachate which was analysed further regarding metals. In addition, the influence of chitosan was studied on compost leachate toxicity. The most important aspect of this paper is to demonstrate the potential of waste chitosan recycling. Thus, the chitosan chelates were subjected to the electrospinning procedure in order to develop new nano-porous structures, such as, for example, conductive textiles.     

Tuning the properties of PVDF or PVDF-HFP fibrous materials decorated with ZnO nanoparticles by applying electrospinning alone or in conjunction with electrospraying

Novel composite nanofibrous materials of poly(vinylidene fluoride) (PVDF) or poly(vinylidene fluoride-cohexafluoropropylene) (PVDF-HFP) and ZnO nanoparticles were prepared by conjunction of electrospinning and electrospraying techniques. Simultaneous electrospinning of concentrated solution of PVDF or PVDF-HFP and electrospraying of suspension of ZnO in diluted PVDF or PVDF-HFP solution enable the preparation of materials consisting of fibers on which ZnO was deposited on the fibers’ surface (design type “on”). These fibrous materials were compared with materials consisting of PVDF or PVDF-HFP fibers in which ZnO was incorporated in the fibers (design type “in”) and which were obtained by one-pot electrospinning of a suspension of ZnO nanoparticles in concentrated PVDF or PVDF-HFP solution. The fiber morphology and the presence of ZnO “in” or “on” the fibers were observed by scanning electron microscopy (SEM) and by transmission electron microscopy (TEM). The effect of the used technique on the type, size and shape of the obtained structures was discussed. The fibrous mats were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), contact angle measurements and mechanical tests as well. It was found that the decoration of fibers with ZnO resulted in increase of their thermal stability and hydrophobicity. The microbiological tests showed that the materials of design type “on” possessed strong antibacterial activity against the pathogenic microorganism Staphylococcus aureus. The results suggest that, due to their antibacterial activity, the obtained composite materials are suitable for wound dressing applications.     

Recent progress on conventional and non-conventional electrospinning processes

Electrospinning is a process of producing micro- and nanoscale fibers using electrostatically charged polymeric solutions under various conditions. Most synthetic and naturally occurring polymers can be electrospun using appropriate solvents and/or their blends. Because of the fascinating properties of electrospun fibers, electrospinning has recently attracted enormous attention worldwide. Initially, this method did not receive much industrial attention due to lower production rates, costs, and lack of interest in size, shape, and flexibility of electrospun nanofibers. However, with the advancement of needleless electrospinning, multiple needles in series, near-field electrospinning techniques, and nanotechnology in particular, this is no longer an issue. This paper outlines the recent progress on the production of various sizes and shapes of fibers using conventional and non-conventional electrospinning processes (e.g., rotating drum and disc, translating spinnerets, rotating strings of electrodes in polymeric solutions, and forcespinning) and presents a complete view of electrospun fiber productions techniques and the resultant products’ applications in different fields to date.     

Properties of thermoplastic composites with cotton and guayule biomass residues as fiber fillers

This study was conducted to evaluate the suitability of using residual plant fibers from agricultural waste streams as reinforcement in thermoplastic composites. Three groups of plant fibers evaluated included cotton burrs, sticks and linters from cotton gin waste (CGW), guayule whole plant, and guayule bagasse. The plant fibers were characterized for physical (bulk density and particle size distribution) and chemical properties (ash, lignin and cellulose contents). A laboratory experiment was designed with five fiber filler treatments, namely control (oak wood fiber as the filler - OWF), cotton burr and sticks (CBS), CBS with 2% (by weight) second cut linters (CBL), CBS with 30% (by weight) guayule whole plant (CGP), and CBS with 30% (by weight) guayule bagasse (CGB). The composite samples were manufactured with 50% of fiber filler, 40% of virgin high-density polyethylene (HDPE), and 10% other additives by weight. The samples were extruded to approximately 32 × 7 mm cross-sectional profiles, and tested for physico-mechanical properties. The CBS and CBL had considerably lower bulk density than the other fibers. Cotton linters had the highest α-cellulose (66.6%), and lowest hemicellulose (15.8%) and lignin (10.5%) of all fibers tested. Guayule whole plant had the lowest α-cellulose and highest ash content. Both CBS and guayule bagasse contained α-cellulose comparable to OWF, but slightly lower hemicellulose. Evaluation of composite samples made from the five fiber treatments indicated that fibers from cotton gin byproducts and guayule byproducts reduced the specific gravity of the composites significantly. However, the CBS and CBL samples exhibited high water absorption and thickness swelling, but the addition of guayule bagasse reduced both properties to similar levels as the wood fiber. The CGP exhibited significantly lower coefficient of thermal expansion. Composite samples with the five different fiber fillers showed similar hardness and nail holding capacity, yet oak fibers imparted superior strength and modulus under flexure and compression with the exception of the compressive modulus of CGB composites. In general, both cotton ginning and guayule processing byproducts hold great potential as fiber fillers in thermoplastic composites.     

Role of elasticity in control of diameter of electrospun PAN nanofibers

A series of poly(acrylonitrile-co-methylacrylate) copolymers (PAN) with varying molecular weight were synthesized by radical copolymerization using α-α′-azobisisobutyronitrile (AIBN) as initiator. These copolymers were dissolved at different concentrations in DMF and electrospun at Minimum electrospinning voltage (MEV) to correlate electrical energy required to perform the mechanical work during the spinning of the fibers. The diameters of the resultant fibers were correlated with the Berry number and average number of entanglements per chain of the spinning solution. It was observed that number of entanglements per chain, which represents the capacity of the polymer system to store elastic energy, could correlate well with the ultimate diameter of the fiber. Interestingly, the diameters of the nanofibers were found to increase linearly with increase in number of entanglements per chain with two distinct regions having transition of the slope at number of entanglement value of 3.5.     

Hydrophilic nonwovens by Forcespinning™ of isotactic polypropylene blended with amphiphilic surfactants

As a widely applied polymer, hydrophilic modification of polypropylene (PP) has been an important research field. Forcespinning? uses centrifugal force to fabricate nanofibers rather than electrostatic force as in conventional electrospinning. The absence of electric fields provides a board opportunity for low dielectric materials and the utilization of centrifugal forces significantly increases the yield compared to electrospinning. Hydrophilic nonwovens from isotactic polypropylene (iPP) melt blended with amphihilic surfactant TWEEN20 and TWEEN60 were obtained by Forcespinning?. The factors were investigated by SEM and DSC, which determined fiber diameter distribution and crystallinity. The meshes showed continuous homogeneity along the length of the fiber when the system was employed at 225 °C and the rotational speed at 14,000 rpm. Blending with surfactants bearing ethoxylate groups led to increased oxygen content of the meshes surface as confirmed by ATR-FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS). XPS results indicated preferential distribution of additives on surfaces. The forcespun meshes exhibited excellent hygroscopicity even when the load of TWEEN20 was 10 %.