Waterborne Nanocomposites Research Articles

Waterborne Nanocomposites with Enhanced Breakdown Strength for High Energy Storage

Polymers have been considered as promising materials for dielectric energy storage because of their high breakdown strength, favorable flexibility, and processability. The achievable energy density...

Crosslinkable acrylic-melamine latex produced by miniemulsion polymerization

Nowadays, crosslinkable polymers are highly demanded in applications where improved thermal, mechanical, and chemical strengths are required. Among crosslinkable polymers, those with film forming capability (e.g., coatings and adhesives) are of particular interest. This work investigated the miniemulsion polymerization of various acrylic monomer formulations in the presence of an iso-butylated melamine-formaldehyde resin with the aim of obtaining waterborne nanocomposites with controlled crosslinkable capabilities. Variation of the acrylic monomer formulation showed a significant influence on the degree of crosslinking, and consequently, on the final properties of the acrylic/melamine nanocomposite particles, their coalesced films at room temperature and those cured at high temperature. Thereafter, these results offer the opportunity of obtaining waterborne acrylic/melamine nanocomposites with different post-crosslinking capabilities.

High performance luminescent thermosetting waterborne hyperbranched polyurethane/carbon quantum dot nanocomposite with in vitro cytocompatibility

Abstract Development of high performance and benign polymeric material still remains a challenge across the globe. Comforting the prevailing challenge, we report in situ and ex situ fabrication of tannic acid based waterborne hyperbranched polyurethane (WPU) nanocomposites as fluorescent and cytocompatible materials by incorporating various weight percentages (0.5, 1.0 and 1.5 wt%) of carbon quantum dot (CQD). CQD was synthesized from corms of Colocasia esculenta having an average size 3.2 nm. The waterborne nanocomposites were cured by using glycerol based hyperbranched epoxy in the presence of fatty acid based poly(amido amine) to obtain the desired thermosets. FTIR, Raman, UV–visible spectroscopy, XRD study and HRTEM analyses confirmed the structural changes occurred upon interaction of CQD with WPU. The thermosets showed a good photo luminescent behavior, which confirmed efficiency of the polymer matrix to prevent solid state quenching. The thermosetting nanocomposites exhibited dose dependent improvement of mechanical (tensile strength ∼4.6 fold, toughness ∼4.2 fold, scratch hardness> 2 fold, impact resistance> 1.25 fold compared to thermoplastic pristine WPU) and thermal stability (maximum 28 °C enhancement). The thermosetting films were found to be biocompatible for in vitro adhesion, proliferation and differentiation of MG 63 osteoblast cells with good cell viability.

Synthesis of poly(butyl acrylate‐co‐methyl methacrylate)/montmorillonite waterborne nanocomposite via semibatch emulsion polymerization

ABSTRACTPoly(butyl acrylate‐co‐methyl methacrylate)‐montmorillonite (MMT) waterborne nanocomposites were successfully synthesized by semibatch emulsion polymerization. The syntheses of the nanocomposites were performed in presence of sodium montmorillonite (Na‐MMT) and organically modified montmorillonite (O‐MMT). O‐MMT was used directly after the modification of Na‐MMT with dimethyl dioctadecyl ammonium chloride. Both Na‐MMT and O‐MMT were sonified to obtain nanocomposites with 47 wt % solids and 3 wt % Na‐MMT or O‐MMT content. Average particle sizes of Na‐MMT nanocomposites were measured as 110–150 nm while O‐MMT nanocomposites were measured as 200–350 nm. Both Na‐MMT and O‐MMT increased thermal, mechanical, and barrier properties (water vapor and oxygen permeability) of the pristine copolymer explicitly. X‐ray diffraction and transmission electron microscope studies show that exfoliated morphology was obtained. The gloss values of O‐MMT nanocomposites were found to be higher than that of the pristine copolymer. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42373.

Theory-Guided Strategy for Nanolatex Synthesis

The synthesis of waterborne nanocomposites in semicontinuous emulsion polymerization was investigated using a theory-guided strategy with the aim of achieving the best balance among small particle size, low surfactant concentration, and sufficiently high solids content. It was found that both kinetic (monomer feeding rate, radical generation rate, and temperature) and colloidal (ionic strength and polymer hydrophilicity) aspects were critical in the process. Waterborne nanoparticles as small as 13 nm were obtained with a solids content/(surfactant/polymer) ratio higher than 7.

Enhancing the performance of exterior waterborne coatings for wood by inorganic nanosized UV absorbers

Enhancing the durability of the architectural wood coatings is essential for a successful commercialization of the forest products. Therefore, this paper is focused on UV resistant waterborne nanocomposites coatings for exterior uses of wood, which were improved with inorganic UV absorbers such as zinc oxide and titanium dioxide nanoparticles. The performance of such nanocomposites coatings applied on black spruce boards was demonstrated trough accelerated weathering. Artificial aging behavior of the coatings was followed by color, gloss and thickness changes. Scanning electron microscopy and transmission electron microscopy was used to investigate nanoparticles dispersion in nanocomposite dry films. Fourier Transform Infrared Spectroscopy was used to characterize the chemical modification of the weathered coatings surface. The results have shown significant improvement in UV-shielding of the nanocomposites coatings. Depending of aging criteria, a selection of the best nanocomposite coatings formulations for exterior wood could be done.

Modeling the equilibrium morphology of nanodroplets in the presence of nanofillers

Waterborne polymer nanocomposites containing carbon nanotubes, clay platelets, laponite disks and other spherical/nonspherical nanofillers have been the focus of many recent investigations. The miniemulsion polymerization has proved to be a powerful technique to create new hybrid waterborne nanocomposites with enhanced properties. It is necessary to understand how the nanofiller shape/size and its compatibility with the phases affects the equilibrium morphology of the polymer nanoparticle to control the morphology and the properties of the resulting polymeric dispersions. With the aid of Monte Carlo simulations, the equilibrium morphology of hybrid monomer nanodroplets in the presence of nanofillers with different characteristics was obtained. A series of morphology maps depending on the nanofiller compatibility with the monomer and water phases and its shape have been obtained. These new maps may help to design and determine the required conditions to synthesize innovative waterborne polymer nanocomposites with specific morphologies through miniemulsion polymerization.

Macroinitiator and Macromonomer Modified Montmorillonite for the Synthesis of Acrylic/MMT Nanocomposite Latexes

A cationic macromonomer, 2-methacryloylethylhexadecyldimethylammonium bromide MA16, and a cationic macroinitiator, cationic acrylic/styrene oligomer end-capped with a nitroxide, were used to modify pristine Na−MMT, to enhance compatibility between the clay platelets and the host acrylic polymer matrix in waterborne nanocomposites. Both cationic species were successfully exchanged in the montmorillonite. The organically modified clays were used for the synthesis of acrylic (MMA/BA)/clay waterborne nanocomposites by miniemulsion polymerization. The 30% solids containing latexes were stable and coagulum free and presented better mechanical, thermal and barrier properties than the pristine acrylic copolymer.

Towards the synthesis of high solids content waterborne poly(methyl methacrylate-co-butyl acrylate)/montmorillonite nanocomposites

Small angle X-ray scattering of Na-montmorillonite (Na-MMT) aqueous dispersions showed that at concentrations below 1.5wt%, clay platelets were fully dispersed with an average distance between platelets higher than 16nm. At higher concentrations (3wt%) platelet–platelet interaction was not negligible and SAXS measurements detected ordered stack structures composed of 2–3 platelets with an average distance of around 14–16nm. Thus, initiating an emulsion polymerization of methyl methacrylate and butyl acrylate in an aqueous phase containing Na-MMT at concentrations below 1.5wt% allowed the production of stable and coagulum free waterborne nanocomposites having 30wt% solids content, with exfoliated structure. The in situ produced poly(methyl methacrylate-co-butyl acrylate)/Na-MMT nanocomposite latexes provided better mechanical, thermal and permeability properties than composites prepared by blending pristine latex with Na-MMT or the pristine copolymer synthesized in the same conditions. Furthermore, for the first time nanocomposite latexes with 45wt% solids content and intercalated morphologies having enhanced mechanical properties were also produced by seeded semibatch emulsion polymerization. The intercalated structure was likely due to the higher clay concentration in the aqueous phase that favoured platelet–platelet interaction, increased the viscosity of the polymeric dispersion and prevented a complete exfoliation.

A Molecular Mechanism for Toughening and Strengthening Waterborne Nanocomposites

A Molecular Mechanism for Toughening and Strengthening Waterborne Nanocomposites