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Thisstudy provides a facile approach to improving the dispersionof graphene in polymer matrix through a synergetic effect betweentwo kinds of two-dimensional (2D) nanofillers. The nanohybrid basedon graphene and boehmite (AlOOH) was synthesized by decorating AlOOHnanoplatelets on the graphene nanosheets. The graphene nanohybrid/ethylenevinyl acetate copolymer (EVA) nanocomposite showed a more homogeneousdispersion than those of composites containing only a single nanomaterial.The obtained nanocomposite exhibited significant enhancements in thermalstability and mechanical properties, compared with those of neat EVAand composites with only graphene or AlOOH. The temperature at 80wt % degradation for the nanohybrid-based nanocomposite was increasedby 27 °C in comparison with that of neat EVA. Nevertheless, onlya 14 °C improvement and no enhancement were observed for theAlOOH- and graphene-based composites, respectively. Additionally,after the incorporation of nanohybrid in EVA, the tensile strengthincreased by 37.1%, from 12.4 to 17.0 MPa. [ABSTRACT FROM AUTHOR]

Composites based on poly(vinyl alcohol) (PVA) and aluminumhypophosphite(AHP) are prepared by solvent blending. The thermal, mechanical, andcrystallinity properties of the composites are studied. AHP remarkablyimproves the char residue yield during the thermal degradation andcombustion of AHP/PVA composites. The flame retardancy of the compositesis obviously improved. The increased char which protects underlyingPVA from heat and oxygen is one of the key reasons for the improvedflame retardancy. The crystallinity of the composites is decreased.The glass transition temperature (Tg)and the storage modulus of the composites are increased. In the compositewith 15 wt % AHP, limiting oxygen index (LOI) reaches 28.0%, UL-94V-0 rating is obtained, Tgis increasedby 7 °C, and the storage modulus is increased by 17.2% in comparisonwith neat PVA. Moreover, AHP/PVA composites keep high transparenceand maintain most of the mechanical properties of PVA, which is advantageousfor the practical application of the composites. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) nanosheets prepared from condensation reaction between melamine and o-phthalaldehyde are first prepared through ball milling and then incorporated into thermoplastic polyurethanes (TPU) by solution mixing. Transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectrometer are applied to characterize COFs nanosheets. It is observed apparently from TEM image that COFs nanosheets are obtained. Successful preparation of COFs nanosheets is proved further by vanishment of typical diffraction peak of COFs at around 23.5° in COFs nanosheets XRD pattern, appearance of quadrant and semicircle stretching of the s-triazine ring at 1568 and 1469 cm -1 in FTIR spectra and N═C bond at 389.5 eV in N 1s high-resolution XPS spectra of COFs nanosheets. The thermal property, combustion behavior and mechanical performance of TPU naoncomposites are also investigated. Incorporation of COFs nanosheets into TPU contributes to char forming of TPU under nitrogen atmosphere and 14.3% decrease of peak heat release rate of TPU. Besides, the elongation at break, Young's modulus, and fracture strength of TPU nanocomposites increase sharply compared with that of neat one.

Herein, the molybdenum disulfide (MoS2) was simultaneously exfoliated and noncovalently functionalized by ultrasonication in a Pluronic aqueous solution and then was used to prepare the poly(ethylene oxide) (PEO) based nanocomposite films. The homogeneous dispersion of MoS2 and strong nanosheets/matrix interfacial adhesion were confirmed by representative electron microscopes. The considerable barrier action of the effective MoS2 nanosheets obviously restricted the ordering of crystal lamellae and the motion of polymer chains and then resulted in the formation of the devastated spherocrystal structure and morphological alterations in the nanocomposites, which were confirmed by polarized optical microscopy and the high value of the glass transition temperature. Importantly, MoS2 nanosheets hold great promise in reinforcing the thermal stability and mechanical property of polymer by increasing the effective volume of MoS2 nanosheets. A substantial reinforcement effect of PEO/MoS2 composite films was achieved: even at a relatively low loading level (0.9 wt %), 88.1% increase in Young's modulus, 72.7% increase in stress-at-failure, and 62.1 °C increment of the temperature corresponding to half weight loss were obtained. These significant reinforcements can be attributed to the gradient interface region, which could effectively transfer the stress from the weak polymer chains to the robust nanosheets, thus endowing the PEO/MoS2 composite films with excellent properties.