Saihua Jiang

Preparation of poly(vinyl alcohol) nanocomposites with molybdenum disulfide (MoS2): structural characteristics and markedly enhanced properties

As a graphene-like layered nano-material, molybdenum disulfide (MoS2) has gained much attention from the materials fields. In our research, MoS2/poly(vinyl alcohol) (PVA) nanocomposites are prepared by solvent blending method. The morphology, thermal properties, fire resistance properties and mechanical properties of the PVA/MoS2 nanocomposites are studied. MoS2 is homogeneously dispersed and partially exfoliated in the PVA matrix as indicated by X-ray diffraction (XRD) pattern, Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) characterization. The thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) results indicate improved the thermal decomposition temperature and the glass transition temperature (Tg). The thermal degradation temperature is increased by 20–40 °C. Meanwhile, the peak of heat release rate (pHRR) and total heat release (THR) are decreased by 33% and 20%, respectively. Storage modulus at 40 °C is increased by 28%, and the tensile strength is increased by 24% upon addition of 1 wt% and 5 wt% MoS2. The improvements in the thermal properties, fire resistance properties and mechanical properties of PVA nanocomposites are attributed to the good dispersion of MoS2, physical barrier effects of MoS2 and strong interactions between PVA and MoS2.

The influence of titanate nanotube on the improved thermal properties and the smoke suppression in poly(methyl methacrylate).

The well-dispersed poly(methyl methacrylate)/titanate nanotube (PMMA/TNT) composites were synthesized by in situ polymerization of methyl methacrylate (MMA) in ethanol solution. Thermal stability and the glass transition temperature of the composites are significantly enhanced with a proper amount of TNTs. The comparison between PMMA/TNTs and PMMA/TiO(2) composites suggests the formation of network in PMMA/TNTs composite. The coaction of dehydration and the network is believed to be the crucial factor which improves the thermal properties. TG-FTIR analysis shows that the amount of organic volatiles of PMMA is significantly reduced and the non-flammable CO(2) is generated after incorporating TNTs. It implies the reduced toxicity of the volatiles. The possible mechanism of the smoke suppression is proposed as the dehydration and adsorption effect of TNTs.

MoS2 Nanolayers Grown on Carbon Nanotubes: An Advanced Reinforcement for Epoxy Composites

In the present study, carbon nanotubes (CNTs) wrapped with MoS2 nanolayers (MoS2-CNTs) were facilely synthesized to obtain advanced hybrids. The structure of the MoS2-CNT hybrids was characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy measurements. Subsequently, the MoS2-CNT hybrids were incorporated into EP for reducing fire hazards. Compared with pristine CNTs, MoS2-CNT hybrids showed good dispersion in EP matrix and no obvious aggregation of CNTs was observed. The obtained nanocomposites exhibited significant improvements in thermal properties, flame retardancy and mechanical properties, compared with those of neat EP and composites with a single CNT or MoS2. With the incorporation of 2.0 wt % of MoS2-CNT hybrids, the char residues and glass transition temperature (Tg) of the EP composite was significantly increased. Also, the addition of MoS2-CNT hybrids awarded excellent fire resistance to the EP matrix, which was evidenced by the significantly reduced peak heat release rate and total heat release. Moreover, the amount of organic volatiles from EP decomposition was obviously decreased, and the formation of toxic CO was effectively suppressed, implying the toxicity of the volatiles was reduced and smoke production was obviously suppressed. The dramatically reduced fire hazards were generally ascribed to the synergistic effect of MoS2 and CNTs, containing good dispersion of MoS2-CNT hybrids, catalytic char function of MoS2 nanolayers, and physical barrier effects of MoS2 nanolayers and CNT network structure.

Influence of g-C3N4 nanosheets on thermal stability and mechanical properties of biopolymer electrolyte nanocomposite films: a novel investigation.

A series of sodium alginate (SA) nanocomposite films with different loading levels of graphitic-like carbon nitride (g-C3N4) were fabricated via the casting technique. The structure and morphology of nanocomposite films were investigated by X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. Thermogravimetric analysis results suggested that thermal stability of all the nanocomposite films was enhanced significantly, including initial thermal degradation temperature increased by 29.1 °C and half thermal degradation temperature improved by 118.2 °C. Mechanical properties characterized by tensile testing and dynamic mechanical analysis measurements were also reinforced remarkably. With addition of 6.0 wt % g-C3N4, the tensile strength of SA nanocomposite films was dramatically enhanced by 103%, while the Youngs modulus remarkably increased from 60 to 3540 MPa. Moreover, the storage modulus significantly improved by 34.5% was observed at loadings as low as 2.0 wt %. These enhancements were further investigated by means of differential scanning calorimetry and real time Fourier transform infrared spectra. A new perspective of balance was proposed to explain the improvement of those properties for the first time. At lower than 1.0 wt % loading, most of the g-C3N4 nanosheets were discrete in the SA matrix, resulting in improved thermal stability and mechanical properties; above 1.0 wt % and below 6.0 wt % content, the aggregation was present in SA host coupled with insufficient hydrogen bondings limiting the barrier for heat and leading to the earlier degradation and poor dispersion; at 6.0 wt % addition, the favorable balance was established with enhanced thermal and mechanical performances. However, the balance point of 2.0 wt % from dynamic mechanical analysis was due to combination of temperature and agglomeration. The work may contribute to a potential research approach for other nanocomposites.

Functionalized graphene oxide/phosphoramide oligomer hybrids flame retardant prepared via in situ polymerization for improving the fire safety of polypropylene

A novel strategy based on functionalized graphene oxide (FGO)/phosphoramide oligomer flame retardant was developed to overcome the challenges of the dispersion of graphene sheets in polymer matrix and the ease of the burn-out of graphene under air atmosphere. Graphene oxide (GO) was modified by 4,4-diaminodiphenyl methane (DDM) and then in situ incorporated into phosphoramide oligomer, resulting in a nanocomposite flame retardant (FRs-FGO) containing exfoliated graphene. Subsequently, the flame retardant (FRs-FGO) was incorporated into polypropylene (PP) and simultaneously compatilized with PP-grafted maleic anhydride. TEM results showed that the FGO was dispersed more uniformly in PP than the bare GO because of the strong interfacial interaction and previous exfoliation of FGO in FRs before blending. The thermal properties investigated by thermogravimetric analysis (TGA) indicated that the addition of FRs-FGO into PP resulted in a significant improvement of thermal stability at elevated temperature with higher char yields. Moreover, the crystallization and fire safety properties of PP composites were also improved by the incorporation of FRs-FGO, including increased crystallization temperature (11.4 °C increase), reduced peak heat release rate (66.9% reduction) and decreased total heat release (24.4% decrease), and decreased fire growth rate index (73.0% decrease). The cone results indicated the simple blending of GO with FRs and exhibited less improvement in fire safety properties than FRs-FGO, which resulted from the improved dispersion and thermal stability of FGO sheets. The flame retardant mechanism was because of the shielding effect of FGO and char layers, which could reduce the release of combustible gases and inhibit the mass and heat transfer between the gas phase and condensed phase.

Ternary graphene–CoFe2O4/CdS nanohybrids: preparation and application as recyclable photocatalysts

Graphene (Gr)-based binary Gr–CoFe2O4 and Gr–CdS or ternary Gr–CoFe2O4/CdS nanohybrids were prepared via a facile solvothermal strategy. It was encouraging to find that the ternary Gr–CoFe2O4/CdS nanohybrids exhibited the highest photocatalytic degradation ability (80%) among all the photocatalysts. The significant enhancement in photodegradation under 40 W daylight lamp irradiation was attributed to graphene acting as a “bridge”, where electrons generated from CoFe2O4 were transferred to CdS by graphene and finally led to separation of electrons and holes. Interestingly, neat CoFe2O4 resulted in increasing concentration of methylene blue (MB) as the irradiation time increased. The phenomenon was ascribed to adsorption of MB molecules on CoFe2O4 in the dark and desorption from the photocatalyst during irradiation, confirmed by our ingenious experiment. Digital photos of the Gr–CoFe2O4/CdS hybrids in an external magnetic field indicated that the ternary photocatalyst could be easily separated from aqueous solution. The recycle measurements of the photocatalyst revealed that the ternary nanohybrids exhibited acceptable photocatalytic stability due to unstable decoration. This work would provide a new insight into the construction of visible light-responsive and magnetic separable photocatalysts with high performances.

Novel CuCo2O4/graphitic carbon nitride nanohybrids: Highly effective catalysts for reducing CO generation and fire hazards of thermoplastic polyurethane nanocomposites

Novel spinel copper cobaltate (CuCo2O4)/graphitic carbon nitride (g-C3N4) (named C-CuCo2O4) nanohybrids with different weight ratios of g-C3N4 to CuCo2O4 were successfully synthesized via a facile hydrothermal method. Then the nanohybrids were added into the thermoplastic polyurethane (TPU) matrix to prepare TPU nanocomposites using a master batch-melt compounding approach. Morphological analysis indicated that CuCo2O4 nanoparticles were uniformly distributed on g-C3N4 nanosheets. Thermal analysis revealed that C-CuCo2O4-7 (proportion of g-C3N4 to CuCo2O4 of 93/7) was an optimal nanohybrid for the properties improvement of TPU. Incorporation of C-CuCo2O4-7 into TPU led to significant improvements in the onset decomposition temperature, temperature at maximal mass loss rate and char yields. The heat release rate and total heat release of TPU/C-CuCo2O4-7 decreased by 37% and 31.3%, respectively, compared with those of pure TPU. Furthermore, the amounts of pyrolysis gaseous products, including combustible volatiles and carbon monoxide (CO), were remarkably reduced, whereas, non-flammable gas (carbon dioxide) increased. Excellent dispersion of C-CuCo2O4-7 in TPU host was achieved, due to the synergistic effect between g-C3N4 and CuCo2O4. Enhancements in the thermal stability and flame retardancy were attributed to the explanations that g-C3N4 nanosheets showed the physical barrier effect and catalytic nitrogen monoxide (NO) decomposition, and that CuCo2O4 catalyzes the reaction of CO with NO and increased char residues.

Comparative study on the thermal stability, flame retardancy and smoke suppression properties of polystyrene composites containing molybdenum disulfide and graphene

As a graphene-like layered nano-material, molybdenum disulfide (MoS2) has gained intensive attention from the materials fields. In our research, MoS2 and graphene sheets (GNS) were used as nanofillers to prepare polystyrene (PS) composites by masterbatch-melt blending. The morphology, thermal stability, fire resistance and smoke suppression properties of the PS composites were studied. The aim of our present study is to compare the effect of MoS2 and GNS on the thermal stability, fire resistance and smoke suppression properties of the PS composites. The cone test results indicate the PS/GNS composites exhibited superior flame retardance over PS/MoS2 composites. The results from TGA exhibits that the addition of MoS2 improved the thermal stability and char residues of the PS composites more obviously, When adding 3 wt% MoS2, T−5%, T−10% and T−50% of the composites are increased to 371, 390 and 428 °C, which are 39, 43 and 31 °C higher than those of PS/3% GNS composites. TG-IR results show that the main decomposition products of PS/MoS2 and PS/GNS composites are aromatic compounds and alkenyl units which are similar to those of pure PS. However, less flammable gas products are released relative to pure PS which further leads to the inhibition of smoke. The improvements in the thermal stability, fire resistance and smoke suppression properties of the PS composites are attributed to good dispersion, physical barrier effects of layered nanofillers and the presence of MoS2 which can promote char formation.

Synergetic effect of ferrocene and MoS2 in polystyrene composites with enhanced thermal stability, flame retardant and smoke suppression properties

As a graphene-like layered nanomaterial, molybdenum disulfide (MoS2) has gained intensive attention from the materials community. In our research, MoS2 is firstly modified with ferrocene (Fe–MoS2) on a large scale and then is used as a nanofiller to prepare PS composites by a masterbatch-based melt blending method. The aim of our present study is to study the synergistic effect of ferrocene and MoS2 on the thermal stability, fire resistance and smoke suppression properties of the PS composites. It was found that the thermal stability of the PS composite was obviously enhanced upon the introduction of 3.0 wt% Fe–MoS2. The cone test results indicated that the PS/Fe–MoS2 composites exhibited superior flame retardance to PS/MoS2 and PS/ferrocene composites. Furthermore, the addition of Fe–MoS2 could improve the smoke suppression properties of PS composites, as evidenced by the reduction of the carbon monoxide production rate and smoke production rate (SPR). The total flammable gaseous products from the PS composites were decreased which further led to the inhibition of smoke. Such a significant improvement in thermal stability, fire resistance and smoke suppression properties was mainly attributed to good dispersion of the modified MoS2 nanosheets, synergistic effects between ferrocene and MoS2 nanosheets, physical barrier effects of MoS2 nanosheets and the presence of ferrocene and MoS2 can promote char formation simultaneously.

Multigram-scale fabrication of organic modified MoS2 nanosheets dispersed in polystyrene with improved thermal stability, fire resistance, and smoke suppression properties

A multigram-scale fabrication method was developed to modify molybdenum disulfide (MoS2) nanosheets with cetyl trimethyl ammonium bromide (CTAB), and the CTAB-modified MoS2 nanosheets (CTAB-MoS2) were applied to improve the properties of polymers. CTAB-MoS2 dispersed well in organic solvents and was incorporated into polystyrene (PS) by a masterbatch-based melt-blending method. The morphology, thermal behavior, fire resistance, and smoke suppression properties of the nanocomposites were studied. The CTAB-MoS2 nanosheets dispersed well in PS and exhibited a partial exfoliation structure. The incorporation of 3 wt% CTAB-MoS2 nanosheets led to an increase in thermal degradation temperature (43–60 °C) and char formation as well as a reduction of the peak heat release rate (PHRR) (20%). Moreover, the addition of CTAB-MoS2 nanosheets significantly decreased the smoke production rate (SPR), the peak specific extinction area (peak-SEA) values (52% reduction), and the gaseous products. The improvements in the thermal stability, fire resistance, and smoke suppression properties of PS nanocomposites were ascribed to good dispersion of modified MoS2 nanosheets, physical barrier effects, and catalytic char function of MoS2 nanosheets.