Jianfei Zhang

Preparation and properties of EDC/NHS mediated crosslinking poly (gamma-glutamic acid)/epsilon-polylysine hydrogels

In this paper, a novel pH-sensitive poly (amino acid) hydrogel based on poly γ-glutamic acid (γ-PGA) and ε-polylysine (ε-PL) was prepared by carbodiimide (EDC) and N-hydroxysuccinimide (NHS) mediated polymerization. The influence of PGA/PL molar ratio and EDC/NHS concentration on the structure and properties was studied. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) proved that hydrogels were crosslinked through amide bond linkage, and the conversion rate of a carboxyl group could reach 96%. Scanning electron microscopy (SEM) results showed a regularly porous structure with 20 μm pore size in average. The gelation time in the crosslink process of PGA/PL hydrogels was within less than 5 min. PGA/PL hydrogels had excellent optical performance that was evaluated by a novel optotype method. Furthermore, PGA/PL hydrogels were found to be pH-sensitive, which could be adjusted to the pH of swelling media intelligently. The terminal pH of swelling medium could be controlled at 5 ± 1 after equilibrium when the initial pH was within 3-11. The swelling kinetics was found to follow a Voigt model in deionized water but a pseudo-second-order model in normal saline and phosphate buffer solution, respectively. The differential swelling degrees were attributed to the swelling theory based on the different ratio of -COOH/-NH2 and pore size in hydrogels. The results of mechanical property indicated that PGA/PL hydrogels were soft and elastic. Moreover, PGA/PL hydrogels exhibited excellent biocompatibility by cell proliferation experiment. PGA/PL hydrogels could be degraded in PBS solution and the degradation rate was decreased with the increase of the molar ratio of PL. Considering the simple preparation process and pH-sensitive property, these PGA/PL hydrogels might have high potential for use in medical and clinical fields.

Production of nano bacterial cellulose from waste water of candied jujube-processing industry using Acetobacter xylinum.

The work is aimed to investigate the suitability of waste water of candied jujube-processing industry for the production of bacterial cellulose (BC) by Gluconacetobacter xylinum CGMCC No.2955 and to study the structure properties of bacterial cellulose membranes. After acid pretreatment, the glucose of hydrolysate was higher than that of waste water of candied jujube. The volumetric yield of bacterial cellulose in hydrolysate was 2.25 g/L, which was 1.5-folds of that in waste water of candied jujube. The structures indicated that the fiber size distribution was 3-14 nm in those media with an average diameter being around 5.9 nm. The crystallinity index of BC from pretreatment medium was lower than that of without pretreatment medium and BCs from various media had similar chemical binding. Ammonium citrate was a key factor for improving production yield and the crystallinity index of BC.

Investigation and fabrication of multifunctional metal composite knitted fabrics

Two types of crisscross-section polyester (CSP)/antibacterial nylon (AN)/stainless steel, multifunctional metal hybrid yarns were produced using a hollow spindle spinning machine. The core yarns were both stainless steel wires. One type used an AN filament as inner wrapped yarn and CSP as the outer wrapped yarn, and the other type had the opposite composition. Furthermore, a circular knitting machine was successfully used to fabricate metal composite knitted fabrics with the hybrid yarns. Results indicated that wrapping numbers affected wicking behavior and drying capability. Electromagnetic shielding effectiveness (EMSE) measurements showed that fabrics with varied lamination angles provided better EMSE than the parallel arrangement. The optimum EMSE measured in this study would reach up to –35 dB within the low-frequency range of 50–425 MHz and nearly –20 dB within the high-frequency range of 300 KHz to 1.47 GHz for a fabric with 0°/45°/90°/–45°/0°/45° lamination angles. Finally, the antibacterial activity of the produced metal composite fabric was assessed against Staphylococcus aureus and Escherichia coli bacteria according to the AATCC 90-2011 standard.

Preparation of γ-PGA hydrogels and swelling behaviors in salt solutions with different ionic valence numbers

In this paper, a novel poly γ-glutamic acid (γ-PGA) hydrogel was successfully synthesized by solution polymerization and ethylene glycol diglycidyl ether (EGDE) was used as crosslinker. The structure and morphology of the γ-PGA was investigated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) techniques. The influence of ionic (Na+, Ca2+ and Fe3+) concentrations, temperature and pH on the swelling degree of γ-PGA hydrogels was studied. The results revealed that the swelling capacity is enhanced with increasing pH, but decreased with increasing ionic concentration. The swelling kinetics study indicated that γ-PGA hydrogels were ion-sensitive and presented more limited swelling kinetics in metal ion solutions with higher ionic valence numbers. The results showed that the pseudo-second-order adsorption kinetics were predominant. Maximum swelling degrees were obtained for γ-PGA hydrogels with 21.03 g g−1 in 0.154 mol L−1 NaCl solution, 8.5 g g−1 in 0.154 mol L−1 CaCl2 solution and 12.8 g g−1 in 0.154 mol L−1 FeCl3 solution. Considering the simple preparation process, the ionic- and pH-sensitive properties, this γ-PGA hydrogel might have high potential to be used in medical and other fields.

Antibacterial properties and electrical characteristics of multifunctional metal composite fabrics

In this research, a hollow spindle spinning machine was used to manufacture the multifunctional metal hybrid yarns with stainless steel wire (SSW) as core material, antibacterial nylon (AN) filaments and bamboo charcoal polyester filaments (BC-PETs) as inner and outer wrapped yarn, respectively. The wrapping numbers of produced metal hybrid yarns varied from 8.0 to 15.5 turns/cm. Furthermore, metal composite woven fabrics were fabricated with the metal hybrid yarns as weft yarns and PET filaments as warp yarns on a loom. These woven fabrics were evaluated in terms of far infrared (FIR) emissivity, anion density, electromagnetic shielding effectiveness (EMSE) and surface resistance. The antibacterial activity of the woven fabrics was assessed against both Staphylococcus aureus and Escherichia coli according two test methods AATCC100-2004 and 90-2011, respectively. The wrapping numbers showed a significant influence on the FIR emissivity and anion density of the produced woven fabrics. The presence of SSW in the hybrid yarns decreased the surface resistance and improved the EMSE of the woven fabrics. EMSE measurement showed that FH-15.5 woven fabrics with 0°/90°/0°/90° lamination angles displayed a better electromagnetic shielding behavior than with 0°/45°/90°/−45° lamination angles.

Determination of electromagnetic shielding and antibacterial properties of multifunctional warp-knitted fabrics

Electromagnetic (EM) radiation, bacterial cross-infection, and electrostatic discharge hazards in working environments produce risks in workplace safety in EM industries and hospitals. Although many kinds of EM-shielding fabrics have been produced, few studies have focused on their antibacterial and other functional characteristics. In this study, a series of multifunctional EM-shielding fabrics possessing EM-shielding, antibacterial, antistatic, and thermal protective functions were produced. A vector network analyzer and a coaxial transmission holder were used to assess the EM-shielding performance of the multifunctional EM-shielding fabrics. The effects of layer numbers and angles of EM-shielding fabrics on the shielding level were investigated. The antibacterial ability of EM-shielding fabrics is essential for wearers who work in environments with poor indoor air quality. The test results showed that these fabrics showed excellent antibacterial activity against Escherichia coli and Staphylococcus aureus based on inhibition zone. The presence of stainless steel wires and bamboo charcoal polyester yarns in the multifunctional fabrics provided great EM-shielding and thermal insulation properties, respectively. Moreover, using different yarns as the back face of the warp-knitted fabrics could also impart different thermal properties for the fabrics. These findings provided technical bases to design personal protective clothing with EM-shielding to mainly protect the workers from EM radiation, bacterial infection, and electrostatic discharge.

Processing and Properties of Multifunctional Metal Composite Yarns and Woven Fabric

Multifunctional metal composite yarns made of crisscross-section polyester (CSP), antibacterial nylon (AN), and stainless steel wires (SSW) were manufactured using a hollow spindle spinning machine. The core yarn, the inner wrapped yarn, and the outer wrapped yarns were SSW, AN, and CSP, respectively. Process parameters such as wrapping material content obviously influenced the tenacity, elongation, and surface morphology properties of the manufactured multifunctional metal composite yarns. These yarns were then woven into fabrics using a rapier loom. Woven fabric WC-8 was evaluated in terms of its mechanical properties, antibacterial activity, and electromagnetic shielding effectiveness (EMSE). Results showed that the use of SSW and AN in the metal composite yarns improved the antibacterial and EMSE of the woven fabric. Thus, these metal composite woven fabrics can be used in manufacturing personal protective clothing to protect humans from electromagnetic radiation and bacterial cross-infection.

Wrinkle-resistant finish of foam technology for cotton fabric

The cotton fabrics with the character of anti-crease were obtained by introducing foam technology. It is observed from experimental results that cross-linking agent, curing temperature and curing time all have significant effects on the wrinkle recovery angle and the mechanical property of fabrics. In addition, foam ratio plays an important role in the process of one-side finished fabric. We found that in the case of same weight gain of cross-linking agent, wrinkle recovery angle of foam technology is bigger than that of conventional finish, while the strength loss of foam finish is smaller as compared to conventional finish.

Electromagnetic shielding, wicking, and drying characteristics of CSP/AN/SSW hybrid yarns-incorporated woven fabrics

To improve the wearing comfort, durability, and antibacterial properties of the electromagnetic (EM) shielding property, a type of multifunction EM shielding woven fabrics which having great liquid transport and drying ability were fabricated in this study. This study aims to investigate theirs liquid transport, drying, and electromagnetic (EM) shielding properties. For this purpose, initially six types of multifunctional crisscross-section polyester (CSP)/antibacterial nylon (AN)/stainless steel wire (SSW) metal hybrid yarns with different wrapping amounts were produced using hollow spindle spinning technique. Conductive woven fabrics were then woven with CSP/AN/SSW metal hybrid yarns as weft yarns, and PET filaments as the warp yarns. The liquid transport and drying ability of the conductive woven fabrics were evaluated in terms of wicking ability and water evaporation rate, which are two vital factors that affect the physiological comfort level of personal protective clothing (PPC). Results indicated that adding CSP yarn in the fabricated EM shielding woven fabric could obviously improve the drying rate of the fabric. The EM shielding behavior of these woven fabrics were analyzed using a vector network analyzer in the frequency range of 300 kHz–3 GHz. Results showed that the wrapping amounts of the metal hybrid yarns significantly affect the wicking and drying abilities of the woven fabrics. In addition, the lamination angles of the fabrics with different amounts of layers remarkably affect their EM shielding characteristics.

Functional Properties and Electromagnetic Shielding Behaviour of Elastic Warp-knitted Fabrics

An investigation was made on the electromagnetic shielding behaviour and other functional properties for manufactured multifunctional elastic warp-knitted fabrics. Bamboo charcoal polyester/Crisscross-section polyester (BC-PET/CSP) blended yarns were used as the back of the warp-knitted fabric while conductive composite yarns were used as the front. The variation in the far infrared emissivity and anion density of elastic-warp knitted fabrics produced with different proportions of BC-PET content were studied in detail. Moreover the electromagnetic shielding effectiveness (EMSE) of the fabrics with different elongation was measured in this study. The experimental results showed that increased elongation almost did not significantly affect the EM shielding behaviour of fabric K1 in the elongation range of 0 - 40%. Finally to increase the EMSE of the fabric, the lamination method was used in this study. EMSE measurement results showed that two layer K1 warpknitted fabrics with 90° interval displayed a better shielding effect against the EM wave compared to that with a 0° interval.