Changhua Liu

Effects of surface functionalized graphene oxide on the behavior of sodium alginate.

The aim of this study was to improve the miscibility between fillers and polymer through modifying the face of graphene oxide (GO). In order to compare the effects of GO and modified graphene oxide (MGO) to sodium alginate (SA), sodium alginate/graphene oxide (SA/GO-n) and sodium alginate/modified graphene oxide (SA/MGO-n) biocomposite films were prepared, then the interaction between nanofillers and matrix was evaluated. The structure, morphologies and properties of biocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Ultraviolet-visible (UV-vis), scanning electron microscopy (SEM) and mechanical tests. The results revealed that strong interactions existed between GO (MGO) and SA. Compared with neat SA film, the maximum level of Youngs moduli (E), tensile strength (σ(b)) and elongation at break (ɛ(b)) of the SA/MGO biocomposites improved by 37.8%, 68.4% and 44.9%, while that of the SA/GO biocomposites improved by 19.6%, 44% and 36.5%.

Preparation and characterization of films based on zirconium sulfophenyl phosphonate and chitosan

Zirconium sulfophenyl phosphonate (ZrSP), Zr(O(3)P-C(6)H(4)SO(3)H)(2), was synthesized and characterized to prepare nanocomposites based on chitosan (CS). The effects of ZrSP on the structure, morphology, and thermal properties, as well as the mechanical properties of the films were investigated by Fourier-transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and tensile tests. FTIR spectroscopy revealed that electrostatic interactions had been formed in the nanocomposites, which improved the compatibility between CS and ZrSP. XRD and SEM results indicated the ZrSP nanoparticles were uniformly distributed in the chitosan matrix at low loading, and obvious aggregations existed at high loading. In addition, compared with neat CS, the values of tensile strength (sigma(b)), elongation at break (epsilon(b)), and water resistance of CS/ZrSP-3 containing 0.6wt% ZrSP had been improved by 60.0%, 69.7%, and 41.8%, respectively.

Properties and structural characterization of chitosan/graphene oxide biocomposites

Novel chitosan (CS)/graphene oxide (GO) biocomposites (CS/GO-n) in the form of films are prepared in a casting and solvent evaporation method. Fourier-transform infrared spectroscopy (FT-IR), X-ray diffractions (XRD), atomic force microscopy (AFM), tensile testing and moisture uptake are used to study the structure and properties of these biocomposites. The results indicated that the biocomposite containing 0.6 wt% GO exhibits high tensile strength (64.42 MPa) with a large elongation at break (38.80%). GO improved the mechanical properties and the water-resistance of chitosan-based biocomposites.

Study of the thermal stability and flame retardant properties of graphene oxide-decorated zirconium organophosphate based on polypropylene nanocomposites

The aim of this study is to reduce the flammability of polypropylene (PP) by adding an organic nano-sized flame retardant into the PP matrix. In order to compare the effects of adding N-containing zirconium organophosphate and graphene oxide (GO) decorated N-containing zirconium organophosphate to PP, PP/zirconium 2-(2-(2-aminoethylamino)ethylamino)ethylphosphonate (PP/Zr(AE)3P) and PP/GO-decorated zirconium 2-(2-(2-aminoethylamino)ethylamino)ethylphosphonate (PP/GO-Zr(AE)3P) nanocomposite films were prepared, and their flame resistance evaluated. The structure and morphology of the novel flame retardants were characterized by Fourier transform infrared (FTIR) spectroscopy, and other properties of the nanocomposites were studied by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), limited oxygen index (LOI), cone calorimeter tests, vertical flame and mechanical tests. The results reveal that both the addition of Zr(AE)3P and GO-Zr(AE)3P improve the flame resistance of PP but GO-decorated films exhibited other advantages. Moreover, the evaluation of the thermal properties demonstrated that the addition of Zr(AE)3P or GO-Zr(AE)3P to PP improves the stability of PP, and leads to a higher char yield at higher temperatures.

Properties and structural characterization of chitosan/poly(vinyl alcohol)/graphene oxide nano composites

Abstract Chitosan (CS)/poly(vinyl alcohol) (PVA)/graphene oxide (GO) nanocomposites in the form of films are prepared in a casting and solvent evaporation method. Fourier-transform infrared spectroscopy (FTIR), X-ray diffractions (XRD), atomic force microscopy (AFM), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), tensile testing and moisture uptake were used to study the structure and properties of these chitosan/poly(vinyl alcohol) /graphene oxide (PCS/GO-n) nanocomposites. The result from tensile testing indicated that the nanocomposite containing 2 wt% GO exhibits high tensile strength (71.21 MPa) with a large elongation at break (51.8%). The high mechanical properties of the nanocomposite films are mainly due to uniform dispersion of GO sheets in the polymer matrix and strong interfacial interactions among components.

Synergistic flame retardant properties of a layered double hydroxide in combination with zirconium phosphonate in polypropylene

High-performance flame retardant nanocomposites were prepared for polypropylene (PP). The nanocomposites consisted of an organic-modified layered double hydroxide (LDH) in combination with zirconium 2-(2-(2-aminoethylamino)ethylamino)ethylphosphonate (ZrP) compounds containing phosphorus and nitrogen. The composition, thermal stability and mechanical properties of the nanocomposites combined with PP were studied by X-ray diffraction, scanning electron microscopy, thermogravimetric analysis and differential scanning calorimetry. The flame retardant behavior was observed using a microscale combustion calorimeter. As an effective synergistic flame retardant, the addition of the nanocomposites resulted in a significant decrease in the heat release rate compared with pure PP. When the load of LDH in combination with ZrP was 5 and 15% (a ratio of 1 : 3), the peak heat release rate was reduced by 28.2%. The flame retardant showed good dispersion in the PP matrix. The improved flame retardant performance may be because LDH and ZrP decomposed to produce non-combustible gases, which diluted the combustible gases, and a compact char layer that acted as a fire barrier.

A novel castor oil-based polyurethane/layered zirconium phosphonate nanocomposites: preparation, characterization, and properties

A new type of layered zirconium glycine-N,N-dimethylphosphonate (ZGDMP), with the functional groups –COOH, has been prepared and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). Situ polymerization method was employed to prepare castor oil-based polyurethane/layered zirconium phosphonate (PU/ZGDMP-n) nanocomposite films. The structure and morphology of ZGDMP in PU matrix have been characterized by XRD, SEM, TEM, and Fourier transform infrared spectroscopy. The results show that the morphology and properties of PU-based nanocomposites greatly depend on the functional groups –COOH because of the chemical reactions and physical interactions involved. The tensile test shows that the tensile strength and elongation at break for the nanocomposite films increase with the loading of ZGDMP as compared to those of the virgin PU.

Enhanced tribological properties in core–shell structured SiO2@GO hybrid fillers for epoxy nanocomposites

SiO2 coated with graphene oxide (GO) hybrids (SiO2@GO) were fabricated by electrostatic self-assembly and introduced into an epoxy polymer (EP) matrix to prepare epoxy composites by a solvent-free curing process. The thermal stability, mechanical properties and tribological behavior of SiO2@GO/EP composites were investigated and compared. It was found that the epoxy composites with the aligned core–shell structure of SiO2@GO improved the thermal stability, as well as excellent mechanical and tribological properties. The low content 0.5 wt% SiO2@GO/EP nanocomposites exhibited nearly 88.4% reduction in the friction coefficient and several orders of magnitude reduction in wear rate, constituting a potential breakthrough for future tribological applications. Compared with unfilled epoxy polymers or epoxy polymers with unmodified fillers, the major increase in the tribological properties of the SiO2@GO/EP composites shows the synergy effect between nano-SiO2 and GO during the wear process. The behavior of nano-SiO2 and GO were probably mostly due to ball-bearing and an ultrathin lamellar effect, respectively. The obtained results indicate that the core–shell structure of SiO2@GO as a more effective synergistic system is a valid method for greatly improving the friction and wear properties and mechanical properties of resin-based composites.