Xingxiang Zhang

Fabrication and Properties of Polyamide-6,6-functionalized Carboxylic Multi-walled Carbon Nanotube Composite Fibers

Polyamide-6,6 (PA66)-functionalized carboxylic multi-walled carbon nanotubes (CMWNTs) were fabricated by in situ polymerization. The composite was melt-spun into fibers. The structures and properties of the PA66-functionalized multi-walled carbon nanotubes (PFNTs) were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), etc. CMWNTs were seen to be uniformly scattered throughout the matrix. Aggregation of CMWNTs was not observed in the fracture surface of the composite fiber. The CMWNTs were not completely pulled out from the matrix, implying strong interactions as a result of functionalization. The incorporation of CMWNTs into PA66 did not have a significant effect on the thermal decomposition temperature of the composites. The effect of CMWNT was on the crystallographic form of the composite. The grain sizes of crystals increased as the CMWNT content increased. The storage modulus significantly increased with the increase in CMWNT content. The tensile strength and modulus of the fibers were significantly improved whereas the strain on the fiber decreased with the increased content of CMWNT.

Mussel-Inspired Polydopamine-Functionalized Graphene as a Conductive Adhesion Promoter and Protective Layer for Silver Nanowire Transparent Electrodes

For the scalable fabrication of transparent electrodes and optoelectronic devices, excellent adhesion between the conductive films and the substrates is essential. In this work, a novel mussel-inspired polydopamine-functionalized graphene/silver nanowire hybrid nanomaterial for transparent electrodes was fabricated in a facile manner. Graphene oxide (GO) was functionalized and reduced by polydopamine while remaining stable in water without precipitation. It is shown that the polydopamine-functionalized GO (PFGO) film adhered to the substrate much more easily and more uniformly than the GO film. The PFGO film had a sheet resistance of ∼3.46 × 10(8) Ω/sq and a transparency of 78.2%, with excellent thermal and chemical stability; these characteristics are appropriate for antistatic coatings. Further reduced PFGO (RPFGO) as a conductive adhesion promoter and protective layer for the Ag nanowire (AgNW) significantly enhanced the adhesion force between AgNW networks and the substrate. The RPFGO-AgNW electrode was found to have a sheet resistance of 63 Ω/sq and a transparency of 70.5%. Moreover, the long-term stability of the RPFGO-AgNW electrode was greatly enhanced via the effective protection of the AgNW by RPFGO. These solution-processed antistatic coatings and electrodes have tremendous potential in the applications of optoelectronic devices as a result of their low production cost and facile processing.

Conductive polypyrrole/viscose fiber composites

Polypyrrole (PPy) was polymerized with pyrrole (Py) as the monomer, FeCl3 as an oxidant and sodium dodecyl benzene sulfonate (SDBS) as the dopant on the surface of viscose fiber (VCF) to prepare the conductive PPy/VCF composites. Fourier transform infrared spectra (FT-IR), thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscope (XPS) proved that the interaction between PPy and VCF formed in the PPy/VCF composites. Three structures of N atoms (imine, amine and cationic atoms) were found in PPy of PPy/VCF composites. The influence of reaction conditions including reaction time, Py concentration, FeCl3 concentration and SDBS concentration on the morphology and the conductivity of PPy/VCF composites was investigated in detail. The orthogonal experiments were designed to determine the optimal reaction conditions: reaction time 5h, Py concentration 0.1 mol/L and FeCl3 concentration 0.25 mol/L. When PPy/VCF composite was washed 50 times in water, the conductivity still kept at 1.5S/cm, and this value was stable for more washing.

Quantitative Analysis of Adulterations in Oat Flour by FT-NIR Spectroscopy, Incomplete Unbalanced Randomized Block Design, and Partial Least Squares

This paper developed a rapid and nondestructive method for quantitative analysis of a cheaper adulterant (wheat flour) in oat flour by NIR spectroscopy and chemometrics. Reflectance FT-NIR spectra in the range of 4000 to 12000 cm−1 of 300 oat flour objects adulterated with wheat flour were measured. The doping levels of wheat flour ranged from 5% to 50% (w/w). To ensure the generalization performance of the method, both the oat and the wheat flour samples were collected from different producing areas and an incomplete unbalanced randomized block (IURB) design was performed to include the significant variations that may be encountered in future samples. Partial least squares regression (PLSR) was used to develop calibration models for predicting the levels of wheat flour. Different preprocessing methods including smoothing, taking second-order derivative (D2), and standard normal variate (SNV) transformation were investigated to improve the model accuracy of PLS. The root mean squared error of Monte Carlo cross-validation (RMSEMCCV) and root mean squared error of prediction (RMSEP) were 1.921 and 1.975 (%, w/w) by D2-PLS, respectively. The results indicate that NIR and chemometrics can provide a rapid method for quantitative analysis of wheat flour in oat flour.

Thermo-regulated sheath/core submicron fiber with poly(diethylene glycol hexadecyl ether acrylate) as a core

Side-chain crystallizable comb-like polymers can be used as polymeric thermal energy-storage materials. Diethylene glycol hexadecyl ether acrylate (C16E2AA) was synthesized with sodium alkoxide using diethylene glycol hexadecyl ether (C16E2) and acryloyl chloride as reactants. C16E2AA was prepared by free radical polymerization to form a comb-like polymeric phase change material, poly(diethylene glycol hexadecyl ether acrylate) (PC16E2AA). A series of sheath/core composite submicron fibers were coaxially electrospun using PC16E2AA as the core and poly(acrylonitrile-co-vinylidene chloride) as the sheath. Results indicate that C16E2AA and PC16E2AA were synthesized in high yield. The average molecular weight and polydispersity index of PC16E2AA were 29,800 g/mol and 3.17, respectively. PC16E2AA melted at 33.8℃ and crystallized at 25.8℃. The melting and crystallization enthalpy for PC16E2AA were 90 and 85 J/g, respectively. PC16E2AA was thermally stable below 326℃. Coaxial submicron fibers with smooth surface and average diameter ranging from 341 to 371 nm were electrospun. The optimum feed rate of the sheath and core components for fabricating thermo-regulated submicron fibers with high enthalpies were 0.125 and 0.375 mL/h, respectively. The fibers can absorb 50 J/g at approximately 37℃ and release 48 J/g of heat at approximately 32℃.

Crystalline structure and phase behavior of N-alkylated polypyrrole comb-like polymers

We report the crystalline structure and phase behavior of a series of comb-like polymers (PPy-Cn), which were prepared via N-alkylation reactions between a pyrrole monomer and n-alkyl bromides (n = 18–26). Analysis by temperature-dependent X-ray diffraction and Fourier transform infrared spectroscopy (FTIR), as well as differential scanning calorimetry reveals that the crystal structure, thermal events and packing mode are affected by PPy backbones, which exhibit stronger rigidity than those of previously reported comb-like polymers. Remarkably, variable-temperature (VT)-FTIR proves the formation of orthorhombic phase at very low temperature, while VT-wide-angle X-ray diffraction only presents the hexagonal phase, illustrating that FTIR is a very sensitive tool for analyzing the micro-packing mode of molecular chains. The enhanced side-chain crystallizable carbon atoms indicate that PPy polymeric backbones play a negative role in the regular packing of nano-crystallites formed by alkyl groups.

Preparation and Characterization of Poly(methyl methacrylate)-functionalized Carboxyl Multi-walled Carbon Nanotubes

An in situ polymerization process was used to prepare poly (methyl methacrylate) (PMMA)-functionalized carboxyl multi-walled carbon nanotubes using carboxylate carbon nanotubes and methyl methacrylate as reactants and benzoyl peroxide as an initiator agent. The functionalized multi-walled carbon nanotubes were characterized using transmission electron microscope, scanning electron microscope, nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetric analysis and Raman. The results indicate that the PMMA chains are covalently linked with the surface of carboxylate carbon nanotubes. The surface morphology is controlled by the content of carboxylate carbon nanotubes in the reactants. The PMMA functionalized multi-walled carbon nanotubes are soluble in deuterated chloroform. The storage modulus and tan magnitude increase as the content of CCNTs increases up to 0.3%.

Novel Dual-Component Microencapsulated Hydrophobic Amine and Microencapsulated Isocyanate Used for Self-Healing Anti-Corrosion Coating

Dual component microencapsulated hydrophobic amine and microencapsulated isocyanate were designed and fabricated for self-healing anti-corrosion coating. In this system, novel hydrophobic polyaspartic acid ester (PAE) and isophorone diisocyanate (IPDI) were microencapsulated respectively with melamine-formaldehyde (MF) as shell via in situ polymerization. To reduce the reaction activity between shell-forming MF prepolymer and PAE, another self-healing agent tung oil (TO) was dissolved in PAE and subsequently employed as core material. With field-emission scanning electron microscopy (FE-SEM) and optical microscopy (OM), the resultant microencapsulated IPDI with diameter of 2–5 μm showed a spherical shape and smooth surface. More importantly, both the morphology and microstructure of microencapsulated PAE enhanced significantly after addition of TO. Fourier transform infrared spectra (FTIR) analysis confirmed the molecular structure of chemical structure of the microcapsules. Thermal gravimetric analysis (TGA) indicated that both kinds of microcapsules exhibit excellent thermal resistance with the protection of MF shell. Furthermore, the self-healing epoxy coating system containing microencapsulated IPDI and microencapsulated PAE/TO was prepared and investigated. From the micrographs of true color confocal microscope (TCCM), the self-healing coating containing dual-component microcapsules showed excellent self-repairing performance compared to single microencapsulated IPDI system, and the optimal content of dual-component microcapsules in epoxy coating was 20 wt % approximately.

Chemical synthesis and characterization of dodecylbenzene sulfonic acid-doped polyaniline/viscose fiber

A dodecylbenzene sulfonic acid (DBSA) doped-polyaniline (PANI) coated conductive viscose fiber (VCF) was prepared by chemical oxidation polymerization in an ethanol/water solution. Fourier transform infrared spectra (FTIR) and XPS proved that an interaction between PANI and VCF formed in the PANI/VCF composites. The mild treatment did not result in the oxidation and degradation of VCF detected by thermal gravimetric analysis (TGA) and mechanical testing. Moreover, the influence of the reaction conditions including reaction time, aniline monomer (ANI) concentration, ammonium persulfate (APS) concentration and DBSA concentration on the morphology and the conductivity of the PANI/VCF composites were investigated in detail. The orthogonal experiments were designed to determine the optimal reaction conditions as follows: ethanol/water ratio (30/70), reaction time (18 h), ANI concentration (0.1 mol L−1), APS concentration (0.125 mol L−1) and DBSA concentration (0.1 mol L−1). When the PANI/VCF composite was washed 40 times in water, the conductivity still remained at 2.5 × 10−2 S cm−1, and this value was stable for more washing.

Antibacterial and absorbent acrylonitrile-vinylidene chloride copolymer fibres

A series of antibacterial and absorbent acrylonitrile (AN)-vinylidene chloride (VDC) copolymer fibres were fabricated by adding micro- or nano-sized silver-impregnated activated carbon (Ag-AC) powders in AN-VDC copolymer-dimethylformamide (DMF) solution, and then extruded through a spinneret into a coagulation bath of DMF-water. The fibres containing less than 25 wt% of Ag-AC were spun smoothly. The structure and properties of the fibres were characterized using differential scanning calorimeter (DSC), scanning electron microscopy (SEM), wide-angle X-ray diffraction, and other universal test methods. The BET specific surface areas of the fibres were determined from nitrogen adsorption isotherms, and the absorbability was measured by methylene blue (MB) absorption. The results show that the tensile strength and strain of the fibre containing 20 wt% Ag-AC are 1.3 cN/dtexs and 30%. The BET specific surface area of this fibre is 198 m2/g. The antibacterial activity of the fibres containing 0.10 wt% silver is excellent, the bactericide efficiency of Escherichia coli and Staphylococcus aureus is above 99%.