Yiding Shen

Micromorphology and phase behavior of cationic polyurethane segmented copolymer modified with hydroxysilane

A series of cationic waterborne polyurethane dispersions (SiPU) modified with hydroxysilane (HPMS) were successfully synthesized based on poly(oxytetramethylene) glycols (PTMG) and isophorone isocyanate (IPDI), and the films were obtained by casting the dispersions on tetrafluoroethylene (TFE) plates. Effects of HPMS content on micromorphology, particle size of the dispersions were studied, as well as thermal properties, phase behavior and surface structure of the films. The particles had the morphology of a solid sphere, with particle size varying from 17.1 nm to 114.4 nm corresponding to the increase of HPMS concentration, which can be attributed to the increase of interfacial tension. XPS spectra indicated the surface migration of Si element in the process of film forming, and the SiPU surface was mainly composed of soft segments. DSC analysis, together with TG-DTG-DTA results demonstrated the HPMS soft segment merged with the transition region of PU matrix, forming part of polyurethane backbone, but an improved microphase separation was observed when HPMS concentration greater than 15%. It was also found that incorporation of flexible HPMS prevented the degradation of polyurethane backbone, resulting in the increase of thermal stability in ultimate copolymer.

Facile approach to fabricate waterborne polyaniline nanocomposites with environmental benignity and high physical properties

Waterborne polyaniline (PANI) dispersion has got extensive attention due to its environmental friendliness and good processability, whereas the storage stability and mechanical property have been the challenge for the waterborne PANI composites. Here we prepare for waterborne PANI dispersion through the chemical graft polymerisation of PANI into epichlorohydrin modified poly (vinyl alcohol) (EPVA). In comparison with waterborne PANI dispersion prepared through physical blend and in situ polymerisation, the storage stability of PANI-g-EPVA dispersion is greatly improved and the dispersion keeps stable for one year. In addition, the as-prepared PANI-g-EPVA film displays more uniform and smooth morphology, as well as enhanced phase compatibility. PANI is homogeneously distributed in the EPVA matrix on the nanoscale. PANI-g-EPVA displays different morphology at different aniline content. The electrical conductivity corresponds to 7.3 S/cm when only 30% PANI is incorporated into the composites, and then increases up to 20.83 S/cm with further increase in the aniline content. Simultaneously, the tensile strength increases from 35 MPa to 64 MPa. The as-prepared PANI-g-EPVA dispersion can be directly used as the conductive ink or coatings for cellulose fibre paper to prepare flexible conductive paper with high conductivity and mechanical property, which is also suitable for large scalable production.

Preparation and properties of waterborne cationic fluorinated polyurethane

Waterborne cationic fluorinated polyurethane (WCFPU) micro-emulsion was prepared by the reaction of isophorone diisocyanate (IPDI), polytetramethyleneether glycol (PTMG1000), 1,4-butanediol (BDO), N-methyldiethanolamine (MDEA), trimethylolpropane (TMP) and perfluoroalkylethyl octanol (FEOH), and then the films of the WCFPU were prepared. The influence on the mechanical properties and water absorption of the films, such as the molar ratio of NCO to OH, the dosage of MDEA, TMP and FEOH, was investigated. Their structure, morphology and heat performance were characterized by fourier transform infared spectrometer (FT-IR), dynamic light scattering (DLS), transmission electron microscope (TEM), X-ray diffraction (XRD), differential scanning calorimeter (DSC) and thermogravimetry (TG). The results revealed that the best mechanical properties and water resistance could be obtained under the condition that NCO/OH molar ratio was 1.25, w(TMP) was 1.1%, w(MDEA) was 7.29% and w(FEOH) was 22.3%. In addition, WCFPU was endowed with low surface energy of its film and the membrane surfaces had excellent water and oil repellency. Furthermore, the thermal stability of the waterborne cationic fluorinated polyurethane increased with the incorporation of perfluoroalkyl chain. And XRD, DSC and TG showed that micro-crystallinity of polyurethane increased with the increase of FEOH, which was benefit to the micro-phase seperation.

Micromorphology and thermal properties of polyurethane/polyacrylate soap-free emulsion in the presence of functional monomers

Novel polyurethane/polyacrylate (PUA) composite emulsions were synthesized by soap-free emulsion polymerization method from methyl methacrylate (MMA), butyl acrylate (BA), and 2-Hydroxyethyl acrylate (HEA) in the presence of PU as seeds and a polymerizable emulsifier-Allyloxy hvdroxyl propanesulfonic salt (AHPS). Effects of the AHPS content on the properties of the emulsions and films were studied. Dynamic light scattering (DLS) result showed that the average diameters and polydispersity were decreased with the increment of AHPS content. Fourier transform infrared spectroscopy (FT-IR) result shows that AHPS was introduced into the PUAS chains. Their thermal stability and Tg of the films increased gradually with augment of AHPS amount in polymer. X-ray photoelectron spectroscopy (XPS) analysis showed that sodium was preferably enriched on the surface of latex particles. Atomic force microscopy (AFM) observation performed the extremely flat membrane.

Study on the self-assembly properties of fluorinated hydrophobically associating polyacrylamide

The self-assembly of a fluorinated hydrophobically associating polyacrylamide (UFPAM) prepared by emulsifier-free ultrasound-assisted radical polymerization was studied using fluorescence spectroscopy (FS), rheological measurements, and dynamic light scattering (DLS). The effects of the degree of mineralization (M), temperature, and the concentrations of ionic surfactants—sodium dodecyl sulfate (SDS) and cetyltrimethyl ammonium bromide (CTAB)—on the self-assembly behavior of UFPAM were explored in detail. The results showed that 2,2,3,4,4,4-hexafluorobutyl methacrylate (FA) was effectively incorporated into the UFPAM. As the concentration of UFPAM increased, the hydrophobic self-assembly behavior of UFPAM increased the apparent viscosity and enhanced the structural network of UFPAM, as indicated by the Ostwald–de Waele power-law model, FS, dynamic rheological measurements, and DLS. The maximum apparent viscosity of the UFPAM solution occurred when the polarity of the solution was enhanced in mineralized solution and the polymer coils were expanded at increased temperature. Provided that the concentration of the ionic surfactant was below its CMC, the addition of CTAB promoted the self-assembly of UFPAM, but this did not occur upon the addition of SDS. When the concentration of the surfactant was above the CMC, the aggregation number increased in the UFPAM–CTAB system, whereas it exhibited a minimum value in the UFPAM–SDS system.

Carboxymethyl fenugreek gum: Rheological characterization and as a novel binder for silicon anode of lithium-ion batteries

The rheology of carboxymethyl fenugreek gum (CFG) is characterized and applied it as a binder for the silicon anode of lithium-ion batteries (LIBs). First, a series of carboxymethyl fenugreek gum (namely CFG-1, CFG-2 and CFG-3) was prepared and characterized by Fourier transform infrared spectrophotometer and hydrogen nuclear magnetic resonance spectrometry studies. In rheological measurements, the CFG solutions show higher flowability, weaker viscoelastic behavior and better thixotropy than that of fenugreek gum (FG) solution. Furthermore, the higher degrees of substitution (DS) of CFG solutions lead to lower apparent viscosity and higher flow index, weaker elastic effect and smaller relaxation time, and higher viscosity recoverability than those obtained for lower DS of CFG solutions. In electrochemical measurements, the polar hydroxyl and carboxyl groups in the CFG skeleton chain provide bonding points between the CFG binders and the silicon electrode to produce binder-silicon bonds, which cause strong hydrogen bonding, and resulted in excellent electrochemical stability and specific capacity. The electrochemical performances were measured via the silicon electrodes with FG and CFG at 5 wt% content. As the DS is increased, the initial Coulombic efficiency can increase from 88.74% to 91.3%. When the electrode undergoes a volume change, the CFG binder with silicon electrodes can hold high capacity of above 1500 mAh/g after 200 charge-discharge cycles. Therefore, the carboxymethyl fenugreek gum as a binder may also be a novel extended binder-design, with applications for silicon anodes of LIBs.

Rheological and fracturing characteristics of a novel sulfonated hydroxypropyl guar gum

A series of sulfonated hydroxypropyl guar gum (SHG) samples with different degrees of substitution (DSs) were prepared, and the SHG solution and SHG fracturing fluid were prepared and analyzed. The SHG aqueous solutions with different DSs all exhibit shear thinning behavior, which is well correlated with the Ostwald-deWaele model. Owing to the electrostatic repulsion of SHG molecular chains, SHG solutions with a higher DS will exhibit weaker thixotropic performance and strong anti-salinity ability. In addition, the SHG fracturing fluids, which were formed by interactions between SHG and organic zirconium, exhibit good temperature- and shear-resistant properties, proppant suspension properties, and salt tolerance. Furthermore, SHG gel-breaking fluids show low interfacial and surface tensions, with low residue content and small core permeability damage. These results provide useful indicators for the applications of SHG in the oil field industry.