Exfoliated Α-zirconium Phosphate Research Articles

Preparation, Properties, and Mechanism of Flame-Retardant Poly(vinyl alcohol) Aerogels Based on the Multi-Directional Freezing Method.

In this work, exfoliated α-zirconium phosphate (α-ZrP) and phosphated cellulose (PCF) were employed to synthesize poly(vinyl alcohol) composite aerogels (PVA/PCF/α-ZrP) with excellent flame retardancy through the multi-directional freezing method. The peak heat release rate (PHRR), total smoke release (TSR), and CO production (COP) of the (PVA/PCF10/α-ZrP10-3) composite aerogel were considerably decreased by 42.3%, 41.4%, and 34.7%, as compared to the pure PVA aerogel, respectively. Simultaneously, the limiting oxygen index (LOI) value was improved from 18.1% to 28.4%. The mechanistic study of flame retardancy showed evidence that PCF and α-ZrP promoted the crosslinking and carbonization of PVA chains to form a barrier, which not only served as insulation between the material and the air, but also significantly reduced the emissions of combustible toxic gases (CO2, CO). In addition, the multi-directional freezing method further improved the catalytic carbonization process. This mutually advantageous strategy offers a new strategy for the preparation of composite aerogels with enhanced fire resistance.

Preparation of Polyethylene Nanocomposites Based on Polyethylene Grafted Exfoliated α-Zirconium Phosphate

Polymer nanocomposites containing well-exfoliated nanoplatelets have been shown to possess greatly enhanced physical and mechanical properties. However, it is still a significant challenge to achieve adequate exfoliation of 2D nanoplatelets in polyolefin matrices due to poor compatibility and associated entropic penalty between 2D inorganic filler and nonpolar polyolefin matrices. Grafting polyolefin chains onto the surfaces of an already exfoliated nanoplatelet is a simple, yet effective solution to this problem. The grafted polyolefin chains on the nanoplatelets can entangle and cocrystallize with the polyolefin matrix, preventing agglomeration. In this study, polyethylene (PE) grafted α-zirconium phosphate (ZrP), ZrP-g-PE, was prepared and blended with the PE matrix. The graft density of ZrP-g-PE was designed to maintain ZrP exfoliation during subsequent blending with the PE matrix. It was found that PE confined crystallization formed in ZrP-g-PE, resulting in the formation of PE crystal orientation perpendicular to the ZrP nanoplatelets. The usefulness of this study for preparation of high-performance polyolefin nanocomposites is discussed.

Preparation of Well-Exfoliated Poly(ethylene-co-vinyl acetate)/α-Zirconium Phosphate Nanocomposites.

Poly(ethylene-co-vinyl acetate) (PEVAc) nanocomposites containing exfoliated α-zirconium phosphate (ZrP) have been prepared using a simple solution mixing method to improve their barrier and mechanical properties. ZrP was pre-exfoliated with a surfactant, followed by additional targeted surface functionalization and surfactant exchange to allow for hydrogen bonding of ZrP with the acetate functionality on PEVAc and to improve ZrP surface hydrophobicity. The solvent is found to play an important role in stabilizing ZrP exfoliation in the presence of PEVAc to retain full exfoliation and homogeneous dispersion upon the removal of the solvent. The PEVAc/ZrP nanocomposite exhibits greatly improved oxygen barrier, melt strength, and mechanical properties. The usefulness of the present study for the preparation of olefinic polymer nanocomposites is discussed.

High performance epoxy nanocomposites based on dual epoxide modified α-Zirconium phosphate nanoplatelets

Epoxy nanocomposites with exfoliated α-zirconium phosphate (ZrP) using proton exchanged polyetheramines as surfactants have previously been demonstrated to show significant improvements anti-corrosion, barrier, and mechanical properties. However, these nanocomposites have a significant reduction in glass transition temperature (Tg). The low Tg of the nanocomposites is caused by detachment of the polyetheramine from ZrP which interferes with the epoxy curing process. Here, ZrP surfaces with covalently bound molecules containing epoxide functional groups were used to achieve ZrP exfoliation in epoxy without sacrificing Tg. By introducing dual epoxide functionalized ZrP, it is possible to achieve exfoliation and self-assembly of ZrP at high loadings in epoxy with greatly increased Young's modulus and significantly reduced thermal expansion coefficient, while maintaining a high Tg. Implication of the present study for preparation of high-performance polymer nanocomposites is discussed.

Improvement of platinum nanoparticles-immobilized α-zirconium phosphate sheets on tracking and erosion resistance of silicone rubber

Novel platinum nanoparticles immobilized on exfoliated α-zirconium phosphate (Pt@ZrP-E) was prepared and the structure of Pt@ZrP-E was characterized by SEM, TEM and XRD. The effect of Pt@ZrP-E on anti-tracking and erosion properties of Pt@ZrP-E/SiR was investigated. It was found that Pt@ZrP-E can be uniformly dispersed in SiR and SiR containing 0.3 ph Pt@ZrP-E could pass 1A 4.5 kV level. TG results showed that the residues of Pt@ZrP-E/SiR with 0.3 ph Pt@ZrP-E at 700 °C increased from 43.4 wt% to 54.0 wt% compared to SiR. According to the thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) results, the release of carbonyl compounds of Pt@ZrP-E/SiR was decreased but that of CH4 was significantly increased, indicating that Pt@ZrP-E was capable of inhibiting the oxidation of methyl groups and facilitate the cross-linking of SiR under high temperature, which results in the formation of a protective ceramic layer, reduce the ablation from electrical arcing and improve the anti-tracking and erosion properties of SiR.

Immobilization of Anti-Inflammatory Drug on Exfoliated α-Zirconium Phosphate as a pH-Responsive Carrier

In this study, the preparation and characterization of a hybrid material of a biologically active drug and α-zirconium phosphate (α-ZrP) were investigated with the aim toward developing a novel drug delivery system. Thus, bromfenac sodium (BFS) as an anti-inflammatory drug was immobilized on α-ZrP hydrogel prepared from the exfoliation of α-ZrP using propylamine. The amount of BFS immobilized on the α-ZrP hydrogel was 6.9 wt%. The release behavior of BFS from the α-ZrP hydrogel was investigated under pH conditions of 2.0, 4.0 and 7.0. An increase in the amount of BFS released could be observed with increasing pH, with quantitative release achieved at pH 7.0 for 360 min. The exfoliated α-ZrP hydrogel showed good performance as a pH-responsive drug delivery carrier.

Flame retardation behavior of polybenzoxazine/α-ZrP nanocomposites

Flame retardation behaviors of polybenzoxazine (PBa) nanocomposites containing various levels of exfoliated α-zirconium phosphate (α-ZrP) nanoplatelets were prepared and confirmed by transmission electron microscopy.

Thermally stable and highly conductive free-standing hybrid films based on reduced graphene oxide

Thermally stable and highly conductive films have been prepared based on thermally reduced graphene oxide and exfoliated α-zirconium phosphate nanoplatelet (ZrP) hybrids. Exfoliated ZrP and graphene oxide (GO) were first mixed in aqueous solution to form a stable dispersion and then cast into free-standing films through flow-directed assembly. Upon annealing at 750 °C in Argon atmosphere, significant amounts of oxidized species were removed from the GO and a noticeable recovery of sp2 structure of the reduced GO sheets was observed. With the incorporation of the inorganic nanoplatelets, the thermal stability and structural integrity of the hybrid films were greatly improved, while the good electrical conductivity of the reduced GO was maintained. Potential applications for graphene-based hybrid films based on the current approach are discussed.

Electrical conductivity and thermal stability of polypropylene containing well-dispersed multi-walled carbon nanotubes disentangled with exfoliated nanoplatelets

The morphology, crystallization behavior, electrical conductivity, and thermal stability of polypropylene (PP) modified with disentangled multi-walled carbon nanotubes (MWCNTs) is reported. Slightly oxidized MWCNT clusters were disentangled in solution by mild sonication in the presence of exfoliated α-zirconium phosphate nanoplatelets. The disentangled MWCNTs were isolated using acid-induced coagulation to precipitate the nanoplatelets, and were subsequently reacted with octadecylamine. The recovered functionalized MWCNTs (F-MWCNTs) are disentangled and easily dispersed in a commercial PP matrix, and serve as more efficient nucleating agents than the untreated MWCNTs. The PP/F-MWCNT composites exhibit an extremely low percolation-like transition in electrical conductivity, which is attributed to the preservation of a random dispersion of disentangled F-MWCNTs upon cooling from the melt. The thermal stability of PP in air is also substantially enhanced at loadings below the percolation threshold due to the tremendous interfacial area between the polymer chains and the free radical scavenging F-MWCNTs. The present approach provides an efficient and potentially scalable route for commercial production of conductive semi-crystalline thermoplastics. The method may be adapted to uniformly disperse MWCNTs in other polymer matrices by appropriate selection of surface functionality.

Epoxy-nanocomposites containing exfoliated zirconium phosphate: Preparation via cationic photopolymerisation and physicochemical characterisation

Gels of exfoliated α-zirconium phosphate in 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylate (hereafter BCDE) were polymerised by a UV-induced process and the resulting nanocomposites were characterised by TEM, X-ray diffraction, thermogravimetric analysis and dynamic-mechanical thermal analysis. Real-time FT-IR spectroscopy was used to investigate the photopolymerisation kinetics. The polymerisation rate of the gels is faster than that of neat BCDE, especially when the filler is functionalised with aminoalcohols (HO(CH 2) n NH 2, with n = 3, 4, 5). The composites exhibit lower T g values in comparison with neat polymerised BCDE. Because of the barrier effect towards oxygen diffusion due to the high aspect ratio of the filler particles, all composites also exhibit enhanced thermal stability.

Preparation and properties of poly(vinyl alcohol)/exfoliated α-zirconium phosphate nanocomposite films

In this work, poly(vinylalcohol)(PVA)/exfoliated α-zirconium phosphate(e-α-ZrP) nanocomposites of various compositions were created by a solution casting method. The α-ZrP compound was synthesized by refluxing. The characteristic properties of the PVA/e-α-ZrP composite films were examined by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and tensile tests. Tensile tests indicated that with the loading of e-α-ZrP, the tensile strength and the elongation at break were increased by 17.3% and 26.6% compared to neat PVA, respectively. It is noteworthy that optimum film properties were obtained with 0.8 wt% e-α-ZrP, and higher proportions of e-α-ZrP, may be related to the aggregation of e-α-ZrP particles and deterioration of the film properties. On the whole, the nanocomposite PVA/e-α-ZrP systems had mechanical and thermal properties which were superior to that of the neat polymer and its conventionally filled composites.

Optical Properties of ZnO Quantum Dots in Epoxy with Controlled Dispersion

Optical properties of monodisperse colloidal ZnO quantum dots (QDs) having various degrees of dispersion in epoxy have been systematically studied. Exfoliated α-zirconium phosphate (ZrP) nanoplatel...

Proton-conducting solid dispersions of silica and zirconium phosphate pyrophosphate

Solid dispersions of α-zirconium phosphate pyrophosphate in porous silica have been prepared starting from mixtures of a tetrapropylammonium oligosilicate solution with exfoliated α-zirconium phosphate. The treatment of the mixture with acetic acid led to the formation of a gel from which, after calcination at 650 °C to remove the organic moieties, the above solid dispersions were obtained. Their surface areas decreased from about 500 to just a few m2 g–1 with decreasing silica percentage, while the surface ion-exchange capacity showed a maximum for a Zr mole fraction of ca. 0.2. The conductivity dependence on the zirconium content qualitatively reflects that of the surface ion-exchange capacity with a maximum (σ= 3 × 10–3 S cm–1 at 100 °C and ca. 97% relative humidity) at a Zr mole fraction of 0.25. For this composition, conductivity measurements were also carried out as a function of relative humidity at room temperature and 100 °C; in both cases the conductivity decreased by about two orders of magnitude when the relative humidity decreased from 60 to 5%, while remaining at least an order of magnitude higher than that of crystalline α-zirconium phosphate under the same conditions. On the other hand, the conductivity of the anhydrous dispersions was always lower than that of crystalline α-zirconium phosphate and decreased with increasing silica content.