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

Effect of filler loading on polymer chain confinement and thermomechanical properties of epoxy/boron nitride (h-BN) nanocomposites

This article examines the effect of the addition of hexagonal boron nitride (h-BN) nanopowder on the polymer chain confinement, thermal, morphological and mechanical properties of the epoxy system.

Layered double hydroxide and zirconium phosphate as ion exchangers for the removal of ‘black crusts’ from the surface of ancient monuments

Two ion exchanger solids (LDH and ZrP) as an innovative tool to remove gypsum from ancient monuments.

Copper oxide nanoparticles in an epoxy network: microstructure, chain confinement and mechanical behaviour

Copper oxide nanoparticles (nCOPs) having octahedral morphology, synthesized through hydrazine reduction reaction were employed to formulate an epoxy based novel nanocomposite. The synthesis of copper oxide nanoparticles was carried out in polyethylene glycol medium to enhance their interfacial adhesion with the epoxy matrix. The extent of conservation of the crystalline nature and octahedral morphology of the nCOP in its epoxy nanocomposites was confirmed by X-ray diffraction and electron microscopy analysis. The mechanical properties including tensile, impact, fracture toughness and surface hardness of epoxy-nCOP nanocomposites were evaluated as a function of nCOP content. The maximum enhancement in strength, modulus, impact strength, fracture toughness and surface hardness of epoxy-nCOP nanocomposites was observed for 5 phr nCOP content. This may be due to the strong interaction between the nCOP and epoxy chains at this composition arising from its fairly uniform dispersion. A quantitative measurement of constrained epoxy chains immobilized by the nCOP octahedra was carried out using dynamic mechanical analysis. The enhancement in the storage modulus is related to the amount of the added nCOP as well as the volume of the constrained epoxy chains in the proximity of nCOP. The behaviour of epoxy-nCOP nanocomposites in this study has been explained by proposing a mechanism based on the distribution of nCOP domains in the epoxy matrix and the existing volume of constrained epoxy chains.

Layered perovskite nanosheets bearing fluoroalkoxy groups: their preparation and application in epoxy-based hybrids

Nanosheets bearing fluoroalkoxy groups were prepared via exfoliation of a CF₃(CF₂)₇C₂H₄O derivative of HLaNb₂O₇·xH₂O for application in epoxy-based hybrids.

Advances in the chemistry of nanosized zirconium phosphates: a new mild and quick route to the synthesis of nanocrystals

Simple addition of zirconyl propionate to phosphoric acid in alcoholic media surprisingly led to the formation, in few minutes, of transparent gels containing solvent intercalated zirconium phosphate (ZrP) nanoparticles with hexagonal shape and a planar size of about 40 nm. With the help of elemental analysis, inductively coupled plasma-optical emission spectrometry (ICP-OES), and (31)P magic angle spinning (MAS) NMR, the nanoparticle composition was formulated as Zr(R)(w)(HPO(4))(x)(H(2)PO(4))(y), in which R can be an hydroxyl or a propionate group. The stoichiometric coefficients for propanol intercalated ZrP are x = 1.43, y = 0.83, and w = 0.32. Solvent elimination at 60 °C gave rise to an increase in the x value and a decrease in the y and w values. X-ray powder diffraction analysis and transmission electron microscopy (TEM) observations showed a concomitant increase in the particle size: planar size and thickness ranged from 90 to 200 nm and from 20 to 85 nm, respectively, depending on the nature of the solvent. A possible mechanism explaining the change in the x, y, and w values, the growth of nanoparticles, and the role of the solvent is proposed. Finally, the possibility of using these gels to disperse the ZrP nanoparticles within the polymer matrix of Nafion117 is shown.

High yield precipitation of crystalline α-zirconium phosphate from oxalic acid solutions

Microcrystalline zirconium phosphate (ZrP) has been synthesized by precipitating a Zr(IV) salt (i.e., zirconium propionate, chloride, or oxide chloride) with H(3)PO(4) from aqueous solutions of oxalic acid (H(2)C(2)O(4)) at 80 °C. Independent of the Zr(IV) salt, crystalline materials have been obtained with reaction yields >90% and reaction time of one day for the following molar ratios: H(3)PO(4)/Zr = 6 and H(2)C(2)O(4)/Zr = 10. The material prepared from Zr propionate (ZrP(prop)) has been further investigated by scanning electron microscopy, thermogravimetry, and ion exchange titrations. Structural characterization has been performed by X-ray powder diffraction and solid state (1)H-(31)P 2D correlation NMR experiments. Structural parameters obtained by Rietveld analysis of powder diffraction data agree with those reported in the literature for single crystal determinations. Moreover, NMR data show that the closest proton environment of the phosphorus atom in ZrP(prop) is the same as in ZrP samples of similar crystallinity prepared according to literature methods.

Photochemical Methods for the Preparation of Complex Linear and Cross-linked Macromolecular Structures

In this contribution, the current state of the art is summarized and an overview of photoinitiating systems for both radical and cationic polymerizations and their potential application in the preparation of complex linear and cross-linked macromolecular structures are described. Recent relevant studies have been devoted to developing novel free radical and cationic photoinitiators having spectroscopic sensitivity in the near-UV or visible range. Photoinitiated controlled radical polymerization methods leading to tailor-made polymers with predetermined structure and architecture are briefly presented. Several synthetic methodologies for the preparation of epoxy and (meth)acrylate based formulations containing clay or metal nanoparticles are also summarized. The nanoparticles are homogenously distributed in the network without macroscopic agglomeration. Applicability to both free radical and cationic systems is demonstrated.