Characterization of the surface properties of cellulosic fibers in fibrous and ground forms by IGC and contact angle measurements

Surface properties of fibrous and ground cotton and linen were investigated by inverse gas chromatography (IGC) and the contact angle with different liquids was also measured on fabrics composed of both fibers. Results proved that dispersion component of surface tension (γ _s ^d ) determined by IGC depends not only on the surface energy, but also on several factors influencing the adsorbability of probe molecules on the cellulosic substrates. For cotton samples, the trapping of n-alkanes among waxy molecules in the outer layer of fibers can be presumed. This effect results in larger γ _s ^d for cotton fibers than for linen in spite of the higher wettability of the linen fabrics. Besides the surface energy and trapping effects, the grinding also influences the γ _s ^d values. Specific enthalpy of adsorption (ΔH _A ^ab ) of polar probes could be determined on all linen samples, but only on the ground cotton sample. Lewis acid-base character calculated for linen and ground cotton samples depends on the same effects as the γ _s ^d does. The similar ΔH _A ^ab values of chloroform (acidic) and THF (basic) measured on each of the samples support the conclusion that the surface character is amphoteric, which is also proved by the high ΔH _A ^ab values of the amphoteric ethyl acetate and acetone probes.     

An investigation on the comparison of wet spinning and electrospinning: Experimentation and simulation

Polysulfonamide (PSA) has been widely used in many fields because of its excellent thermodynamic properties. In this study, PSA fibers were prepared separately via two different spinning ways, including conventional wet spinning and electrospinning. Fluid motion of wet spinning and electrostatic field of electrospinning were modeled using finite element analysis to investigate the spinning process. The properties of fabricated PSA fibers were characterized systematically by scanning electron microscope (SEM), fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), thermal gravity analysis (TGA) and electronic strength tester. Based on the simulation and theoretical analysis of spinning process, it was found that the extruding force of the wet spinning is larger than that of the electrospinning. The larger extruding force makes the alignment of macromolecules inside fiber relatively uniform, and a higher proportion of crystallization happens. Accordingly, the mechanical properties and thermal stability of PSA fibers could be improved due to a higher proportion of crystallization. The experimental results of mechanical strength and TG test are coincided with the simulation results. PSA fiber prepared by wet spinning has better thermal stability and mechanical properties than that fabricated by electrospinning.     

Electrical properties of graphene/waterborne polyurethane composite films

Graphene is classified as a carbon-based material. Structurally, graphene is made up of carbon-based two-dimensional atomic crystals and a one atom thick planar sheet of sp²-bonded carbon atoms. This sort of arrangement in graphene makes it a unique material with exceptional mechanical, physicochemical, thermal, electrical, optical, and biomedical properties. Methods for graphene-based fabric production mainly use graphene-based materials such as graphene (G), graphene oxide (GO), and reduced graphene oxide (rGO) coated on fabric or yarn. Waterborne polyurethane (WPU) is one of the most rapidly developing and active branches of polyurethane chemistry. More and more attention is being paid to graphene-coated fabrics owing to their low temperature flexibility, the presence of zero or very few VOCs (volatile organic compounds), water resistance, pH stability, superior solvent resistance, excellent weathering resistance, and desirable chemical and mechanical properties. It is used as a coating agent or adhesive for fibers, textiles, and leather. Also, graphene-containing materials have been used to enhance the properties of WPU. In this study, graphene/WPU composite solution and film was prepared to conduct basic research for developing electrical heating textiles which is not harmful to the human body, flexible and excellent in electrical properties. Graphene/WPU composite solutions were prepared with a graphene content of 0, 2, 4, 8, and 16 wt%, and graphene/WPU film was prepared with solution casting method. The graphene contents were analyzed for their surface morphology, electrical properties, and electrical heating properties.     

Preparation of PHEMA/nHAP nanocomposites via <Emphasis Type="Italic">in situ</Emphasis> polymerization in supercritical carbon dioxide for biomedical applications

Poly(2-hydroxyethylmethacrylate) (PHEMA)/hydroxyapatite (HAP) nanocomposites were synthesized through a new route involving nano-sized HAP (nHAP) particles or modified nHAP mixed with monomer 2-hydroxyethylmethacrylate via in situ polymerization in supercritical carbon dioxide (scCO₂). Fourier-transform infrared spectroscopy showed phosphate peak increased with nHAP content in composite. X-ray diffraction patterns of PHEMA/nHAP revealed the presence of crystallized nHAP. Thermogravimetric analysis showed that the ultimate nHAP content in PHEMA/nHAP composites is consistent with its initial amount. Scanning electron microscopy revealed that nanocomposite particles are much smaller than PHEMA particles. PHEMA/nHAP composites with average diameter of approximately 600 nm were obtained in scCO₂ with 94 % yield. Mechanical properties of PHEMA/nHAP nanocomposites were better than those of PHEMA, and compressive modulus and strength of composites with 30 wt.% nHAP were 193 and 29 MPa, respectively. Nanocomposite adsorption toward bovine serum albumin was evaluated, and results indicated that analyte adsorption amount can reach up to 282 mg/g.     

The grafting of recycled polyol from waste polyurethane foam onto new polyurethane and its impact on shape recovery and water vapor permeation

Recycled polyols from waste polyurethane (PU) foams were grafted onto PU to improve the properties such as tensile strength, shape recovery, low-temperature flexibility, and water compatibility. The recycled polyol was either purified by column chromatography before grafting or was used directly for grafting. The soft segment melting temperature of PU did not notably increase with the addition of polyol, whereas the glass transition temperature increased with increased polyol content. The tensile strength sharply increased at low polyol content and decreased at high polyol content, while the strain at break did not significantly change with an increase in polyol content. The shape recovery at 10 oC notably improved compared with unmodified PU and remained high after four cyclic tests. Polyol-grafted PU demonstrated better lowtemperature flexibility and reduced the water vapor permeability of PU membranes. Overall, grafting recycled polyol onto PU significantly improved the tensile stress, shape recovery, and low-temperature flexibility of PU.     

Synthesis and characterization of a novel charring agent and its application in intumescent flame retardant polyethylene system

A novel charring agent poly(pentaerythritol spirocyclic phosphorusoxy spirocyclic diethanolamine borate) (PPSPSDB) was synthesized successfully with diethanolamine borate (DEAB) and spirocyclic pentaerythritol bisphosphorate disphosphoryl chloride (SPDPC), which was combined with ammonium polyphosphate (APP) to endow linear low-density polyethylene (LLDPE) with flame retardance. The structure of PPSPSDB was characterized by FTIR and 1H-NMR. The study of thermal stability of various LLDPE composites showed that PPSPSDB/APP system could effectively improve the thermal degradation and thermal-oxidative stability of the char residues, and PE3 containing 30 wt% APP/ PPSPSDB with a 2 weight ratio left the highest amount of char residue at 800 oC. The results of flammability revealed that PE3 had the best combination property; the limited oxygen index value was 29.6, and vertical burning reached UL-94 V-0 rating, and the tensile strength and notched impact strength were 11.853 MPa and 28.8 kJ/m2 respectively. The investigation of structure and morphology of char residue indicated that the compact foaming char layer, as a good barrier against the transmission of heat and volatiles, was formed for PE3 during combustion.     

Improvement of toughness for the hyaluronic acid and adipic acid dihydrazide hydrogel by PEG

New applications call for many new requirements. In order to improve the toughness of aldehyde hyaluronic acid (A-HA) and adipic acid dihydrazide (ADH) hydrogel, the poly(ethylene glycol) (PEG) was added. PEG content and molecular weight have little effect on the gelation time, and the composite hydrogels can form in situ within 20 seconds at room temperature. The press test showed that the hydrogels containing PEG possessed a better compression resistance, after pressed more than five times, the composite hydrogels could restore. Rheological properties were measured to evaluate the working ability and the effect of PEG on hydrogels. By analyzing the shear viscosity (η _γ=0.01), yield stress (σ ₀) and threshold shear stress (σ _c ), the addition of PEG can make the structure of composite hydrogels get loose and improve the shear resistance. Especially, PEG800 can enhance the antishear ability obviously. The amplitude sweep tests showed a broad linear viscoelastic region, indicating a wide processing range. In the meanwhile, we also found that PEG can improve the optical transmittance of xerogel evidently.     

Obtaining medical textiles including microcapsules of the ozonated vegetable oils

In this paper, it was aimed to obtain disposable medical textiles having antibacterial and wound healing properties, as well as biological adaption. For this purpose, the St. John’s Wort oil and flax seed oil were ozonated, and the oils were capsulated with arabic gum. The produced ozonated oils were characterized through FTIR and TGA analyses, as well as the properties of antibacterial, wound healing, and biological adaption were investigated. The produced microcapsules were examined via optical microscope and FTIR. The characterized microcapsules of the ozonated oils were applied to the textiles with padding method. After the applications, the fabrics were researched with SEM and FTIR analyses; in addition the antibacterial and wound healing properties and biological adaption of the textiles were also investigated. The results showed that the St. John’s Wort oil and flax seed oil were successfully ozonated and microcapsulated. The microcapsules of the oils could be applied to the fabric samples with the determined application recipe. The ozonated oils and the fabric samples applied microcapsules of the ozonated oils gained high antibacterial and wound healing property. In addition, the fabric samples were produced as having biological adaptation.     

Preparation and performance as PEM of sulfonated pre-oxidized nanofiber/SPEEK composite membrane

Building proton transfer channel is an important strategy to optimize the proton transfer process of the proton exchange membrane (PEM). In this work, sulfonated pre-oxidized nanofibers were prepared by solution blowing of polyacrylonitrile (PAN) nanofibers followed by pre-oxidization and sulfonating, and the nanofibers were composited with SPEEK to enhance its performance as PEM. The results of the proton conductivity verified that the employment of sulfonated pre-oxidized nanofibers improved the proton conductivity. Meanwhile, the introduction of the sulfonated pre-oxidized nanofibers realized the upgrades of the thermostability and water absorbency of the membrane, and led to the decrease of the swelling property and methyl alcohol’s permeability of the material. It is indicated that the composite membrane is promising materials for PEM fuel cells.     

Electroneutral cornstarch by quaternization and sulfosuccinylation to improve the adhesion of cold starch paste to raw cotton for low-temperature sizing

The objective of this research was to survey the effects of starch quaternization and sulfosuccinylation on the adhesion of cold starch paste to raw cotton fibers for cotton warp sizing at low temperature. Acid-thinned cornstarch (ATS) was quaternized and then sulfosuccinylated to introduce 3-(trimethylammonium chloride)-2-hydroxypropyl and sulfosuccinate substituents onto its backbones. The electroneutrality of starch samples prepared was achieved by maintaining a constant mole ratio (5.3:1) of the two substituents. A series of electroneutral cornstarch (ECS) samples with different levels of the substituents were derived by altering the feed ratio of the modifying reagents to starch for determining desirable level of starch modification. Adverse influences of cotton wax and starch retrogradation on the adhesion of cold starch paste to raw cotton fibers were evaluated to illustrate the effectiveness of starch quaternization and sulfosuccinylation. It was found that the modification was able to alleviate the adverse influence of starch retrogradation and ameliorate the adhesion to the fibers at low temperature. Higher level of the modification led to less retrogradation and resulted in strong adhesion. Furthermore, the adverse influence of cotton wax on the adhesion could be eliminated after a pre-wetting treatment of raw cotton warps with hot water. The adhesion of ECS paste to raw cotton at 60 °C was statically the same as that of ATS at 95 °C when total DS of ECS was 0.0443 or higher.