Polyethylene Terephthalate Composite Films with Enhanced Flame Retardancy and Gas Barrier Properties via Self-Assembly Nanocoating.

The flammability and gas barrier properties are essential for package material. Herein, a highly-oriented self-assembly nanocoating composed of polyvinyl alcohol (PVA) and montmorillonite (MMT) was prepared for endowing polyethylene terephthalate (PET) films with excellent flame retardancy and gas barrier properties. The specific regular nanosheet structure of the PVA/MMT composite nanocoating was confirmed by Fourier transform infrared (FTIR) and X-ray diffraction (XRD). Thermogravimetric analysis (TGA) and the vertical burning test (VBT) suggested that the thermal stability and flame-retardancy of the coated PET films were considerably improved with more pick-up of the resulting nanocoating. When reaching 650 °C, there was still 22.6% char residual left for coated PET film, while only 6% char residual left for pristine PET film. During the vertical burning test, the flame did not spread through the whole PET film with the protection of PVA/MMT nanocoating, and no afterflame was observed. Scanning electron microscopy (SEM) is consistent with vertical burning test, proving that the thermal stability and flame retardancy of coated PET films were considerably enhanced with the increment of PVA/MMT. Thanks to the multi-layer structure, PVA/MMT nanocoating could effectively improve the gas barrier properties of PET films, and the oxygen vapor transmittance rate and water vapor transmittance rate of PET films were more than four hundred times lower and 30% lower than those of neat PET film. Our work demonstrates that bi-functional flame retardant and gas barrier materials could be gained via constructing inorganic/organic highly-oriented self-assembly nanocoating, which is promising in the area of packaging.

A green approach for tunable fluorescent and superhydrophobic monodisperse polysilsesquioxane spheres.

HYPOTHESIS: Typically, calcination at high temperature could bring fluorescence to hybrid silica spheres prepared with 3-aminopropyltriethoxysilane and tetraethylorthosilicate, but they tended to be hydrophilic. Further extra modification is required to gain superhydrophobicity, which might probably block the fluorescence. Short side organic chains are very thermostable at high temperature. Therefore, it might be possible to produce superhydrophobic and fluorescent hybrid silica spheres through the co-condensation of organosilanes with short side organic chains and calcination at high temperature. EXPERIMENTS: Methyltrimethoxysilane (MTMS) and vinyltrimethoxysilane (VTMS) were co-condensed to prepare polysilsesquioxane (PSQ) spheres, which were subsequently calcinated at high temperature. The impact of MTMS/VTMS ratio on the chemical structures, fluorescence and wettability was investigated, and the applications of PSQ spheres were expanded. FINDINGS: The PSQ spheres with the ratio of MTMS/VTMS as 3/1 and 2/2 exhibited strong fluorescence, and the calcination did not destroy the superhydrophobicity for the remaining of abundant methyl, vinyl, or ethyl groups. Our study provides an extremely green, simple and effective approach to prepare thermostable, fluorescent and superhydrophobic monodisperse silica spheres without using rare earth element, gold, conjugated polymer, phorsphore, fluoride chemical or organic solvent.

Mechanically strong and electrically stable polypyrrole paper using high molecular weight sulfonated alkaline lignin as a dispersant and dopant.

Flexible and conductive polypyrrole (PPy) paper shows the potential use in electromagnetic shielding, antistatic packaging, and electrochemical materials due to its low cost and facile manufacturing procedure. However, the poor mechanical strength and relatively low electrical stability of PPy paper is still challenging. In this study, we use horseradish peroxidase polymerized sulfonated alkaline lignin (HSAL) as a dispersant and dopant for PPy and demonstrate mechanically strong and electrically stable PPy paper by a combination of multiple impregnations and in-situ polymerization. The abundant sulfonic, carboxyl, and phenolic hydroxyl groups of HSAL could significantly improve the interfacial interaction between cellulose fibers and PPy. Meanwhile, its high molecular weight facilitated the uniform distribution of pyrrole along the fiber axial direction during in-situ polymerization. As a result, the resulting PPy paper exhibits enhanced mechanical properties and electrical stability, as well as high conductivity (24.84 S cm-1). More significantly, we investigated the influences of the dosage of HSAL and the cycles of multilayer impregnations on the electrical and mechanical properties of PPy paper. This work sheds light on the design and fabrication of flexible and conductive PPy paper with superior mechanical robustness and stable electrical performance.

Flame retardant and hydrophobic coatings on cotton fabrics via sol-gel and self-assembly techniques.

Nanocoatings consisting of ammonium polyphosphate (APP), sodium montmorillonite (MMT), and vinyltrimethoxysilane (VTMS) were prepared via self-assembly and in situ sol-gel techniques and applied onto cotton fabrics to achieve both flame retardancy and hydrophobicity. The impacts of APP concentration on the hydrophobicity and fire resistance of the coated fabrics were investigated. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) characterization results verified the hydrolysis-condensation reaction of VTMS and the formation of Si-O-Si network structure. X-ray diffraction (XRD) proved the formation of a layered structure based on MMT nanosheets in the coatings. Both vertical flame test (VFT), limiting oxygen index (LOI), thermogravimetric analysis (TGA) and microscale combustion calorimeter (MCC) characterization were conducted to evaluate the flame retardancy, thermostability and heat release behavior of the coated cotton fabrics, respectively. The results suggested that a higher concentration of APP is beneficial for both hydrophobicity and flame retardancy of the coated substrates. Overall, our research provides a facile and very effective approach to prepare flame retardant and hydrophobic multifunctional coating for cotton fabric and other substrates.

Synthesis and hydrogenation application of Pt-Pd bimetallic nanocatalysts stabilized by macrocycle-modified dendrimer.

Different generations of poly(propylene imine) (G n -PPI) terminated with N-containing 15-membered triolefinic macrocycle (G n M) (n = 2, 3, 4, 5) were prepared. The bimetallic nanoparticle catalysts G n M-(Pt x /Pd10-x ) (x = 0, 3, 5, 7, 10) were prepared by the synchronous ligand-exchange reaction between G n M and the complexes of Pt(PPh3)4 and Pd(PPh3)4. The structure and catalytic properties of G n M-(Pt x /Pd10-x ) were characterized via Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, energy-dispersive spectroscopy and inductively coupled plasma atomic emission spectroscopy. The novel bimetallic Pd-Pt nanoparticle catalysts stabilized by dendrimers (DSNs) present higher catalytic activities for the hydrogenation of dimeric acid (DA) than that of nitrile butadiene rubber (NBR). It can be concluded that bimetallic Pd-Pt DSNs possess alloying and synergistic electronic effects on account of the hydrogenation degree (HD) of DA and NBR. Furthermore, the HD of DA and NBR shows a remarkable decrease with the incremental generations (n) of G n M-(Pt3/Pd7) (n = 2, 3, 4, 5).

Highly monodisperse polysilsesquioxane spheres: synthesis and application in cotton fabrics.

Highly monodisperse methyl-functionalized, vinyl-functionalized, and thiol-functionalized polysilsesquioxane spheres (MPSQ, VPSQ, and MPPSQ spheres) have been successfully prepared through a one-pot emulsion approach with one organosilane as sole precursor in aqueous medium. The morphology, size distribution, and chemical structure were characterized by SEM, DLS, FT-IR, solid NMR, XRD, etc. The thermodecomposition and hydrophobicity of these spheres were investigated with TGA and water contact angle measurement. Our research turns out that the organofunctional groups play a key role in thermostability and hydrophobicity of polysilsesquioxane spheres, MPSQ, and VPSQ spheres possess better thermostability than MPPSQ spheres, the order of hydrophobicity is as follows: MPSQ>VPSQ>MPPSQ. Cotton fabrics can become superhydrophobic when treated with methyl- or vinyl-functional silica spheres.