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.     

Effect of poly(amid–imide)/Al2O3 hybrid with various ratios on the physicochemical properties of poly(vinyl alcohol) nanocomposites films

To study the effect of the various ratios of poly(amide–imide)/Al₂O₃ nanocomposites (PANC)s on the mechanical and thermal properties of nanocomposites films, poly(vinyl alcohol) (PVA)/PANCs based on various ratios of 2, 4, and 6 wt% were prepared and characterized. In the first step, the surface of alumina nanoparticles was treated with 15 wt% of biosafe diacid and consequently, about 10 wt% of these modified nanoparticles were loaded into the poly(amide–imide) matrix. Then, various contents of the obtained PANCs were incorporated into a PVA solution using a sonochemical treatment. The effects of PANC on the structure and morphology of PVA matrix were studied using powder X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, atomic force microscopy (AFM), and thermal gravimetric analysis (TGA). The results show that the tensile strength and decomposition temperature were improved as the portion of PANC into PVA matrix are increased from 2 to 6 wt%. Also, AFM pictures of the fracture surfaces of PVA/PANCs showed a significantly rougher surface than the neat PVA.     

Thermal stability and flammability of butadiene–styrene rubber nanocomposites

Heterobimetallic oxalato complex precursors, manganese(II)tetraaquatris(oxalato)lanthanate(III)hexahydrate (MnOLa), cobalt(II)pentaaquatris(oxalato)lanthanate(III)trihydrate (CoOLa), nickel(II)pentaaquatris(oxalato)lanthanate(III)hexahydrate (NiOLa) and copper(II)diaaquatris(oxalato)lanthanate(III)monohydrate (CuOLa) of the type, M₃[La(C₂O₄)₃(H₂O) _m ]₂·nH₂O have been synthesized in aqueous medium. The precursors were characterized by elemental analysis, IR, electronic spectral and powder X-ray diffraction studies. The good crystalline nature with monoclinic structures predominates in MnOLa and NiOLa whereas triclinic structures were found in CoOLa and CuOLa. The solid-state thermal behaviour of the precursors was explored using TG, DTG and DTA in air. The MnOLa generated a mixture species consisting mainly of MnO₂, Mn₃O₄, Mn₅O₈, La₂O₃ and LaMn₇O₁₂ at 1000 °C through the formation of several intermediate species at 380 and 570 °C. The studies revealed that CoOLa led mainly to LaCoO₃ and La₂CoO₄ along with some oxides of both the cobalt and lanthanum at 1000 °C. In case of nickel analogue the mixture species identified at 1000 °C are mainly of La₂NiO₄, La₂O₃, Ni₂O₃ and NiO_2. In case of CuOLa the product at 1000 °C consisted of La₂CuO₄, La₂Cu₂O₅ and oxides of copper and lanthanum. The nature of decomposition of the precursors in nitrogen were seen from DSC study and the kinetic parameters i.e., E ^* , lnk ₀, ΔH ^# , ΔS ^# and order of reaction of all the steps were evaluated and discussed.     

Intercalation of pyridine and quinoline intoα-zirconium phosphate

The uptake of pyridine and quinoline into-zirconium phosphate has been investigated by the batch method. The effect of solvent on the reactions was also studied. Pyridine was taken up from ethanol, chloroform, carbon tetrachloride, ethanol-water, and acetone-water solutions, but not from pure acetone at 25°C. Water accelerated the uptake of pyridine. These facts indicate that a water molecule was involved in the uptake reaction of pyridine.Quinoline was taken up easily in an ethanol-water solution at 25°C, and in an ethanol solution at the boiling point. Two reactions — ion exchange and intercalation — occur on taking up the quinoline. An IR spectrum of the quinoline form is reported.     

Morphology, crystallization and mechanical properties of poly(ɛ-caprolactone)/graphene oxide nanocomposites

A series of nanocomposites based on poly(ε-caprolactone) (PCL) and graphene oxide (GO) were prepared by in situ polymerization. Scanning electron microscopy observation revealed not only a well dispersion of GO but also a strong interfacial interaction between GO and the PCL matrix, as evidenced by the presence of some GO nanosheets embedded in the matrix. Effects of GO nanofillers on the crystal structure, crystallization behavior and spherulitic morphology of the PCL matrix were investigated in detail. The results showed that the crystallization temperature of PCL enhanced significantly due to the presence of GO in the nanocomposites, however, the addition of GO did not affect the crystal structure greatly. Thermal stability of PCL remarkably increased with the addition of GO nanosheets, compared with that of pure PCL. Incorporation of GO greatly improved the tensile strength and Young’s modulus of PCL without a significant loss of the elongation at break.     

Chemical–physical behavior of hydrogels of poly(vinyl alcohol) and poly(ethylene glycol)

New hydrogels based on polyethylene glycol (PEG) and poly(vinyl alcohol) (PVA) of different degrees of hydrolysis were synthesized. To form the network the PEG was modified at their ends with acyl chloride groups to be used as the crosslinking agent. The compositions of the hydrogels were between 50% and 90% by weight of PEG and PVA of various degrees of hydrolysis were used. It was found that the degree of hydrolysis of the PVA and the PEG content influence the equilibrium water content of the hydrogel. The process of swelling of all the hydrogels prepared followed a second-order kinetics.     

Intercalation of phenylethylamines intoα-zirconium phosphate and characterization of intercalates

The intercalation of phenylethylamines into-zirconium phosphate has been investigated by the pH titration method.dl-1-Phenylethylamine (dl-PEA) is taken up in two stages. New phases were obtained: Zr(HPO₄)₂(dl-PEA) · H2O in the first, and Zr(HPO₄)₂(dl-PEA)_/43· H₂O in the second stage. 2-Phenylethylamine (2-PEA) also is loaded in two stages, but the first end point is not observed clearly. A new phase, Zr(HPO₄)₂(2-PEA)₂ · H₂O has been formed at the second stage. The new phases have been characterized by elemental analysis, X-ray diffractometry, thermal analysis and IR spectroscopy.     

Direct and stepwise intercalation of alkylalcohols intoα-zirconium phosphate

Intercalation of alkylalcohols into -zirconium phosphate was investigated at 25°C and/or under reflux.n-Alcohols having two to five carbons and 2-propanol were taken up at 25°C. These alcohols, andn-hexanol and heptanol, also intercalated under reflux.n-Alcohols having eight to eighteen carbon atoms intercalated when a stepwise method was employed. 2-Butanol and tertiary amylalcohols intercalated under reflux using a butanol intercalate as a starting material. Ethanol-to-butanol intercalates were unstable at room temperature, losing alcohols and changing to -zirconium phosphate. The particle size of the -zirconium phosphate did not affect the intercalation of alcohols.     

Morphological structures of poly(vinylidene fluoride)/montmorillonite nanocomposites

Poly(vinylidene fluoride) (PVDF)/montmorillonite (MMT) nanocomposites were prepared by melt blen- ding a kind of organically modified montmorillonite with PVDF. The morphological structures of the nanocomposites were studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). The re- sults indicate that organically modified montmorillonites are in the form of intercalation, exfoliation, and fragments in the PVDF matrix. For the composites, the (001) peak position of MMT was found to shift to a lower angle in XRD patterns, and some MMT fragments could be observed under TEM. MMT loading was favorable to producing the piezoelectric β phase in the PVDF matrix and caused internal stress in α crystals. At the same time, the crystallinity and spherulite size of PVDF decreased with the MMT content. MMT induced β phase is stable even at high temperatures (160℃). For these changes in morphological structures, some possible explanations were proposed based on the experimental re- sults.     

Viscoelastic behaviors of poly(ε-caprolactone)/attapulgite nanocomposites

Nanocomposites based on biodegradable poly(ε-caprolactone) (PCL) and attapulgite (AT) were prepared by solution blend. The morphology and rheological behaviors of the blends were examined. SEM observation showed that AT nano-rods were well dispersed in the PCL matrix in a nanometer scale at low AT content and a severe aggregation would happen at high AT content. The rheological behaviors of the polymer/fibrous clay nanocomposite samples were investigated by an Advanced Rheometric Expansion System with parallel plate geometry. The effects of AT content on the viscoelastic behaviors of the PCL/AT nanocomposites were also confirmed by rheological analysis. The apparent activation energies of flow were calculated by the Arrhenius equation.     

Flame retardancy properties of α-zirconium phosphate based composites

α-Zr phosphate (hereafter referred to as ZrP) based composites were prepared by melt blending in order to improve the flame retardancy properties of polyamide 6 (PA6), polyethylene terephthalate (PET), polypropylene (PP) and ethylene vinyl acetate copolymer (EVA). Different morphologies are distinguishable by electron microscopy: PA6-ZrP seems to be a nanocomposite by Transmission Electron Microscopy (TEM) whereas PET-, PP- and EVA-ZrP blends appear micro-composites by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) analyses. ZrP acts as flame retardant in PA6 reducing the total heat evolved and consequently the heat release rate during the combustion measured by cone calorimetry. Moreover, ZrP reduces the flammability of PET and EVA acting in synergistic effect with phosphorous based flame retardants. Indeed, it is showed that it is possible to reduce the amount of phosphorous flame retardant adding ZrP to reach UL94 classification V0 for both polymers.     

The synthesis and applications of α-zirconium phosphate

The synthesis of α-ZrP with a range of crystallinity is of high importance due to the different requirements in various applications.Nanosized crystalline α-ZrP is typically obtained by refluxing amorphous ZrP in concentrated H₃PO₄ solutions.Microcrystalline α-ZrP are obtained by direct precipitation in the presence of either HF or oxalic acid which are used as complexing agents for zirconium.These larger crystals are useful as ion-exchangers in column-type applications as ...     

Synergetic effect of poly(vinyl butyral) and calcium carbonate on thermal stability of poly(vinyl chloride) nanocomposites investigated by TG–FTIR–MS

In order to improve poly(vinyl chloride) (PVC) thermal stability, poly(vinyl butyral) (PVB) matrix and calcium carbonate nanoparticles were incorporated in plasticized PVC. Thermal properties of these composites were investigated by thermogravimetry analysis coupled with mass spectrometry and Fourier transform infrared spectroscopy (FTIR). This approach highlighted the efficiency of both PVB and CaCO₃ as HCl scavengers by postponing both the onset degradation temperature and the HCl release. Moreover, a synergetic effect was evidenced regarding the HCl release. Finally, kinetic parameters of the PVC first degradation stage, determined using the Flynn–Wall–Ozawa’s method, revealed a significant increase of the activation energy by incorporation of CaCO₃ in the presence or not of PVB.     

Preparation and characterization of microspheres based on blend of poly(lactic acid) and poly(ɛ-caprolactone) with poly(vinyl alcohol) as emulsifier

In this paper, microspheres were prepared by oil-in-water (o/w) emulsion solvent evaporation method. Biodegradable polymer such as blend of poly (lactic acid) (PLA) and poly(?-caprolactone) (PCL) with certain compositions and characteristics was used to prepare the microspheres with poly(vinyl alcohol) (PVA) as an emulsifier. This study observed the microspheres particle’s size distribution at various concentrations of PVA (1%, 1.5%, 2%, and 2.5% PVA). The PVA volume variations effects during the process (50, 100, 150, 200, and 250 mL) were also observed. The blend of PLA and PCL is formed only by physical interaction between them. This can be seen from the FTIR spectrum which shows both PLA and PCL component. The microspheres physical size and appearance were observed by optical microscope (MO). The overall results of this study showed that the formula which used 50–150 mL of 2.5% polyvinyl alcohol produced the microspheres with the most uniform size distribution.     

Reentrant behavior of poly(vinyl alcohol)–borax semidilute aqueous solutions

 The reentrant behavior of Poly(vinyl alcohol) (PVA)–borax aqueous semidilute solutions with a PVA concentration of 20 g/l and borax concentrations varies from 0.0 to 0.20 M was investigated using dynamic light scattering (DLS) and dynamic viscoelastic measurements. Two (fast and slow modes) and three (fast, middle, and slow) relaxation modes of PVA semidilute aqueous solutions without and with the presence of borax, respectively, were observed from DLS measurements. The fast and middle relaxation modes were q ²-dependent (q is the scattering vector) characteristic of diffusive behavior; however, the slow modes were q ³-dependent, characteristic of intraparticle dynamics. The experimental results showed that the slow relaxation mode dominates the DLS relaxation. The DLS slow mode relaxation time, τ_s, and the viscoelastic modulus G′(ω) and G′′(ω) data had a similar trend and demonstrated reentrant behavior as the borax concentration was increased from 0.0 to 0.20 M, i.e. τ_s, G′(ω), and G′′(ω) fluctuated with increasing borax concentration. The excluded-volume effect of polymers, charge repulsion among borate ions bound on PVA molecules, and intermolecular cross-linking didiol–borate complexation caused an expansion of the polymer chain; however, the screening effect of free Na⁺ ions on the negative charge of the borate ions bound on PVA and intramolecular cross-linking didiol–borate complexation led to a shrinkage of the polymer chain. The reentrant behavior was the consequence of the balance between expansion and shrinkage of the PVA–borate complex. Received: 26 March 1999/Accepted in revised form: 3 September 1999     

Remarkably improved toughness and thermal stability of poly (vinyl chloride) (PVC)/poly (α-methylstyrene-acrylonitrile) (α-MSAN) blend with the assistance of two impact modifiers

The key drawback of impact modifier-toughened polymer is that the improved toughness is accompanied by loss in stiffness. Surprisingly, poly (vinyl chloride) (PVC)/poly (α-methylstyrene-acrylonitrile) (α-MSAN) blend was toughened without loss in stiffness by simply combining two impact modifiers-chlorinated polyethylene (CPE) and acrylic resin (ACR). The prepared blend's impact strength was 3.0 times higher than PVC/α-MSAN/CPE blend and 18.6 times higher than pure PVC/α-MSAN blend. An impressive thermal stabilizing effect was also achieved when CPE and ACR were combined. The improved toughness could be attributed to the overlap of the stress field between different impact modifiers, which help to form the continuum percolation of stress volume under impact loading.     

Synthesis and structural characterization of sol–gel derived titania/poly (vinyl pyrrolidone) nanocomposites

Non hydrolytic sol–gel method was employed to synthesize pure anatase TiO₂ nanocrystals using tetra isopropyl orthotitanate and poly vinylpyrrolidone as precursors. The structural analyses of the prepared samples were carried out using Fourier transform infrared spectroscopy (FT-IR), thermo gravimetric and differential thermal analysis (TG–DTA), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). The capping of PVP around TiO₂ nanoparticles was confirmed by FT-IR spectroscopy, the interaction being via bridging oxygens of the carbonyl (C=O) and the nanoparticle surface. The XRD, Raman and TEM results indicate that the prepared samples had a pure anatase nano-TiO₂ structure. The particle size analysed by TEM ranged between 7 and 12 nm. The size of the nanocrystals evaluated from the XRD spectra and TEM micrograph is well in agreement. The spacing for the crystal planes was also determined using the ImageJ program applied to the TEM micrographs.