Hybrid Latex Research Articles

Waterborne Casein-Based Latexes with High Solids Content and Their High-Throughput Coating Optimization

Over the past few years casein-based latexes have attracted increasing interest because of their good film-forming properties. This paper investigates the use of acrylic/casein hybrid latexes with a solids content of 35% in a coating application, which involves the evaluation of nonformulated latexes as binders, the high-throughput formulation with different commercial agents (cosolvents, wetting agents, and defoamers) and the formulation optimization using statistic multivariable analysis. Latexes were obtained by emulsifier-free emulsion polymerization of acrylic monomers in the presence of a chemically modified casein containing 10 vinyl bonds per molecule. The optimized clear coats formulated from the hybrid latexes showed a good performance requiring a reduced formulation-agents concentration, which could be an important benefit from an environmental viewpoint. Together the above results demonstrate that the casein biobased latexes represent a promising alternative for the development of a new genera...

Synthesis and characterization of polymer-silica hybrid latexes and sol-gel-derived films

Sol-gel derived organic-inorganic hybrid systems were obtained by applying alkaline-catalyzed co-hydrolysis and copolycondensation reactions of tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), isobutyltriethoxysilane (IBTES), diethoxydimethylsilane (DMDES), and vinyltriethoxysilane (VTES), respectively, into a polymer latex functionalized with vinyltriethoxysilane (VTES). The properties of the latex hybrid materials were analyzed by FTIR, water contact angle, environmental scanning electron microscopy (ESEM), TEM and AFM analysis, respectively. FT-IR spectra confirmed that the chemical structures of the sol-gel derived organic-inorganic materials are changed as function of inorganic precursor and SiOSi networks are formed during the co-hydrolysis and copolycondensation reactions. The water contact angle on the sol-gel latex film containing TEOS+VTES increased to 135°±2 compared to 65°±5 for the blank latex, due VTES incorporation into latex material. TGA curves of hybrid sample modifies against neat polymer, the thermal stability being influenced by the presence of the inorganic partner. ESEM analysis showed that the latex hybrid films prepared with different inorganic precursors were formed and the Si-based polymers were distributed on the surface of the dried sol-gel hybrid films. TEM and AFM photos revealed that the latex emulsion morphology was modified due to the VTES incorporation into system.

Donut-like hybrid latex comprising discrete thermoplastic lobe and thermosetting shell

Abstract We achieve a donut-like polystyrene (PS) latex structure in a dispersion polymerization system where a low dose of octavinyl polyhedral oligomeric silsesquioxane (OVPOSS) is essential for inducing the asymmetric growth of latex particles. The evolution of donut shape is sensitive to polarity of dispersion medium, monomer conversion and substituted group of styrenic monomer. This asymmetric growth originates from the attaching of OVPOSS oligomers, i.e. nanoblocks (NB), to the surface of early PS particles, which launches a colony on each particle. Subsequent anchoring of OVPOSS surrounding the colony leads to a spread of NB, which concurrently impedes the growth of PS latex over the area they settle. While the uncovered patch continues expanding through propagation of PS radical chains, the region with a spreading of NB is consequently transformed to a concave thermosetting cap on a portion of individual PS particles. This anisotropic structure demonstrates unique viscoelastic characteristic shown by the latex films prepared.

Silica encapsulation by miniemulsion polymerization: A novel approach of efficient chemical functionalization on silica nanoparticles

Abstract Hybrid latex particles with core-shell nanostructure were prepared via miniemulsion polymerization. Copolymer of (methyl methacrylate-butyl acrylate-methacrylic acid) was formed the shell on the surface of modified SiO2 nanoparticles as the core. In order to create compatibility between inorganic and polymeric phases, modification of SiO2 nanoparticles was performed with methylene diphenyl diisocyanate and 2-hydroxy ethyl methacrylate with an optimized procedure for the first time, and then miniemulsion polymerization was carried out in the presence of modified SiO2. The products of each step were characterized. The results of DLS, TEM and SEM analyses proved the formation of encapsulated hybrid latex particles. DLS and SEM data revealed that the sizes of nanocomposite particles vary between 60 and 120 nm for 0–10 wt% of the modified SiO2 nanoparticles. Thermal stability and thermo-mechanical properties of the obtained nanocomposite films were studied by TGA and DMTA, respectively. It was found that the best improvement of properties is achieved for nanocomposite containing 7 wt% modified silica nanoparticles.

Synthesis of Polymer/Silica Hybrid Latexes by Surfactant-Free RAFT-Mediated Emulsion Polymerization

The reversible addition–fragmentation chain transfer (RAFT) polymerization technique was used to synthesize random copolymers of poly(ethylene glycol) methyl ether acrylate) (PEGA) and n-butyl acrylate (BA) and terpolymers of acrylic acid (AA), PEGA and BA with a trithiocarbonate reactive end-group. These macromolecular RAFT agents (macro-RAFTs) were subsequently adsorbed at the surface of size-monodisperse colloidal silica particles with diameters varying between 40 and 450 nm. Adsorption isotherms for both macro-RAFTs could be well fitted to the Langmuir adsorption model, the AA-based macro-RAFT agent showing however a lower maximum adsorption. The adsorbed macro-RAFT agents were subsequently chain extended with a mixture of methyl methacrylate (MMA) and BA by starved feed emulsion polymerization. Cryo-TEM analysis of the resulting hybrid latexes synthesized in the presence of the P(AA-co-PEGA-co-BA) terpolymers resulted in multipod-like particles while the P(PEGA-co-BA) copolymers showed the formation ...

Novel Polymer Clay‐Based Nanocomposites: Films with Remarkable Optical and Water Vapor Barrier Properties

The impact of varying the copolymer composition of styrene–co‐butyl acrylate copolymers on the dispersion of montmorillonite (MMT) clay and the effect thereof on the transparency and water vapor barrier properties of the resultant films is assessed. The hybrid latexes containing MMT clay concentrations of 10–30 wt% are prepared using miniemulsion polymerization. The morphology of the resultant latexes shows that the MMT particles are predominantly adhered onto the surface of the latex particles. However, the transparency of the films suggests a fair dispersion of the MMT platelets in the matrix. The thickness‐normalized light transmittance for copolymers with 40 and 50 mol% styrene only decreases from 70% in the neat films to 50% in the nanocomposite films containing 30 wt% clay. The best optical properties are observed for the copolymers with 30 mol% styrene, in which the light transmittance only decreases from 85% (unfilled film) to 60% in the nanocomposite films containing 30 wt% clay. Overall, the water vapor barrier properties are much higher in the copolymer films with 30 mol% styrene due to the unique morphological organization of MMT platelets in the matrix. image

Epoxy-acrylic core-shell particles by seeded emulsion polymerization

We developed a novel method for synthesizing epoxy-acrylic hybrid latexes. We first prepared an aqueous dispersion of high molecular weight solid epoxy prepolymers using a mechanical dispersion process at elevated temperatures, and we subsequently used the epoxy dispersion as a seed in the emulsion polymerization of acrylic monomers comprising methyl methacrylate (MMA) and methacrylic acid (MAA). Advanced analytical techniques, such as scanning transmission X-ray microscopy (STXM) and peak force tapping atomic force microscopy (PFT-AFM), have elucidated a unique core-shell morphology of the epoxy-acrylic hybrid particles. Moreover, the formation of the core-shell morphology in the seeded emulsion polymerization process is primarily attributed to kinetic trapping of the acrylic phase at the exterior of the epoxy particles. By this new method, we are able to design the epoxy and acrylic polymers in two separate steps, and we can potentially synthesize epoxy-acrylic hybrid latexes with a broad range of compositions.

Polylactide/Montmorillonite Hybrid Latex as a Barrier Coating for Paper Applications.

We developed a paper coating for the potential application in food packaging based on polylactide and montmorillonite. It is applied to the paper in the form of a stable, water-based latex with a solid content of 25–28 wt %. The latex is prepared from a commercially available polylactide, surfactants, montmorillonite, a plasticizer, chloroform (to be removed later) and water by an emulsion/solvent evaporation procedure. This coating formulation is applied to the paper substrate by bar-coating, followed by hot-pressing at 150 °C. The coated papers achieved up to an 85% improvement in water vapor transmission rates when compared to the pristine papers. The coating latex is prepared from inexpensive materials and can be used for a solvent-free coating process. In addition, the ingredients of the latex are non-toxic; thus, the coated papers can be safely used for food packaging.

Aqueous extraction of Ricinodendron heudelotii oil and direct miniemulsion polymerization of the oil-in-water fraction

This paper reports the aqueous extraction of Ricinodendron heudelotii oil and synthesis of Candida rugosa lipase catalyzed in-situ hydrolyzed emulsions of the extracted fraction for production of high-value products. The extracted oil-in-water emulsion fraction was polymerized with (meth)acrylate monomers by miniemulsion polymerization technique to synthesize environmental friendly and waterborne hybrid latex binders for coating systems. The aqueous extraction was carried out at 40°C by ultrasonication for 30min. The in-situ enzymatic hydrolysis reaction was carried at 37°C and the yield of the cream (oil-in-water emulsion) fraction is 6.7% (%wt). This fraction contains more than 80% of the total extracted oil and it is further polymerized with methyl methacrylate and butyl acrylate via miniemulsion polymerization in the presence and absence of sodium dodecyl sulfate (SDS) as an external emulsifier. The final degree of hydrolysis is 69.12%. The monomer conversion with SDS is 74.41% and without SDS the conversion is 62.00%. The hybrid latexes were characterized by Fourier transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), particle size analysis and thermo-mechanical analysis (TMA). The morphology of latexes was also evaluated by transmittance electron microscopy (TEM) and film surface topography with atomic force microscopy (AFM) techniques.

Chemical modification of TiO2 nanoparticles as an effective way for encapsulation in polyacrylic shell via emulsion polymerization

Abstract Encapsulation of inorganic nanoparticles by polymers is one of the interesting research topics that lead to the synthesis of nanocomposites. These nanocomposite materials comprise the properties of both organic polymer and inorganic nanoparticles. Here, hybrid latex particles with core–shell nanostructure were prepared via semi-batch emulsion polymerization. Copolymers of (methyl methacrylate-butyl acrylate) and (dimethylaminoethyl methacrylate-butyl acrylate-acrylic acid) were formed as the inner and outer layers, respectively on the surface of modified TiO 2 nanoparticles as the core. In order to create compatibility between inorganic and polymeric phases, modification of TiO 2 nanoparticles was performed with glycidyl methacrylate with an optimized procedure for the first time and then emulsion polymerization was carried out. The products of each step were fully characterized. The results of dynamic light scattering, TEM and SEM analyses proved the formation of encapsulated hybrid latex particles. DLS and SEM data revealed that the sizes of nanocomposite particles vary between 85 and 120 nm for 0–5 wt% of the modified TiO 2 nanoparticles. Physico-mechanical properties of the obtained nanocomposite films were studied by DMTA. It was found that using only 3 wt% of modified TiO 2 improved those properties of resulting films remarkably.

Surface topography and hydrophobicity of waterborne fluorinated acrylic/silica hybrid coatings

Fluorinated acrylic/silica hybrid latexes have been prepared by mini-emulsion polymerization in the presence of silica nanoparticles functionalized by 3-(methacryloxy) propyltrimethoxysilane. The hybrid particle size and morphology were determined by transmission electron microscopy (TEM). Surface topography of the coating was investigated by atomic force microscopy (AFM) and chemical composition of the surface was analyzed by energy dispersive spectroscopy (EDS). Surface hydrophobicity of the coating was evaluated by water contact angle measurement. The results showed that polymeric latex particles were grafted onto silica. The presence of modified silica in fluorinated acrylic coating favored enrichment of fluorine at the film surface, which contributed to the hydrophobicity of the hybrid film.

Dielectric relaxations of Acrylic-Polyurethane hybrid materials

In this work we present a dielectric relaxation study of Acrylic/Polyurethane polymers synthesized via miniemulsion photo-polymerization. Three different samples, both parts of the synthesized hybrid latex (SOL and GEL fractions) and a full acrylic sample as reference have been considered. Besides dielectric experiments using Broadband Dielectric Spectroscopy (BDS) technique, complementary Differential Scanning Calorimetry measurements have been performed. The thermodynamic characterization outcomes evidence very similar characteristics of the glass transition phenomena among the investigated samples without any signature of melting/crystallization. However BDS experiments show three well resolved dielectric relaxation processes above Tg, two of them evidence marked differences among the samples. A detail study allows us to provide a molecular origin for these three dielectric relaxation processes in connection with the sample characteristics. In particular, our results show that the characterization of these hybrid Acrylic/PU by BDS can provide access to some of the structural features that would ultimately influence the adhesives properties.

In‐situ formation of metal nanoparticle/acrylic polymer hybrid and its application to miniemulsion polymerization

ABSTRACTWe present in‐situ formation of metal nanoparticle/acrylic polymer hybrid and its application to prepare hybrid latex particles by miniemulsion polymerization. On the surface of a silver nanoparticle/silica nanoparticle/acrylic polymer hybrid layer formed in‐situ on a polyethylene terephthalate (PET) substrate, a copper film is deposited using electroless copper deposition. Silver nanoparticles, which are formed in‐situ via the reduction of silver ion by radical species and subsequent annealing, work as a catalyst for the electroless deposition. Miniemulsion polymerization via the in‐situ formation of nanoparticles affords nanoparticle/acrylic polymer hybrid latex particles and polymer particles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42675.

Waterborne acrylic–casein latexes as eco-friendly binders for coatings

Abstract The use of casein as renewable resource to produce eco-friendly hybrid latexes has an increasing importance in industrial applications especially for high performance waterborne coatings. This work describes the synthesis of hybrid acrylic–casein latexes by emulsion polymerization of acrylic monomers in presence of varied casein concentration, and in absence of emulsifier which is usually a challenge for preparing stable nanocomposite latexes. The production and microstructure characterization of the casein–acrylic nanoparticles, as well as the properties of the films obtained from the hybrid latexes are here reported. The synthesized acrylic–casein latexes are able to form films with promising properties for a potential application as waterborne bio-based coatings.

Hybrid latex particles preparation with seeded semibatch emulsion polymerization

Abstract Hybrid latex particles of modified nano silica and polystyrene were prepared by seeded semibatch emulsion polymerization. The block copolymer of styrene (St) and vinyltrimethoxysilane was synthesized by reversible addition-fragmentation chain transfer polymerization using as a modifying agent for improving the silica dispersion property in St. In seeded semibatch emulsion polymerization, hybrid latex particles were prepared by feeding a monomer mixture or emulsion component that contained modified silica. The effects of the feeding material, feeding rate and SLS concentration of the emulsion components on the St conversion (instantaneous conversion and cumulative conversion), the resultant latex particles size, distribution and morphology were discussed. With the St monomer mixture at a 5.0 g/h feeding rate, the instantaneous conversion was approximately 75%, and the resultant latex particles Z average diameter and particle size distribution was 99.5 nm and 0.06, respectively. The modified silica was uniformly distributed at the seed latex surface. The prepared film surface exhibited more bright spots, and convex structures were observed by atomic force microscopy. The Si atom content was 2.5%, as measured by X-ray photoelectron spectroscopy.

Photoactive self-cleaning polymer coatings by TiO2 nanoparticle Pickering miniemulsion polymerization

Titanium dioxide Pickering stabilized methyl methacrylate/n-butyl acrylate (MMA/BA) copolymer latexes were synthesized by miniemulsion polymerization. The particle size of the hybrid latexes was controlled by the concentration of TiO2 used as stabilizer; the larger the concentration, the smaller the particle size. The hybrid latexes formed coherent films with honey comb structures, the opacity of the films increased with the amount of TiO2. The photocatalytic activity of the hybrid films was assessed by coating concrete specimens and analyzing the capabilities to degrade Rhodamine B under UV-light exposure. The films showed excellent self-cleaning activity and it was found that the photocatalytic activity index was little affected by the concentration of TiO2 and the roughness of the film. The kinetic of the photocatalytic reaction was controlled by the diffusion of the Rhodamine B from the inner of the film to the interface.

Polystyrene‐montmorillonite core–shell particles via Pickering emulsion polymerization and their use as reinforcing additives for polypropylene and ethylene vinyl acetate

Solid particles can be used as stabilizers for oil/water (o/w) emulsions instead of the conventional surfactants. Emulsion polymerization of styrene, as an example of polymerizable oil, was started in the current study after ultrasonication of the monomer into aqueous phase with aid of montmorillonite nanoplatelets as solid stabilizer. Imaging using a field emission scanning electron microscopy equipped with energy dispersive X‐ray unit as well as transmission electron microscopy proved the formation of polystyrene/montmorillonite as core–shell hybrid latex particles via Pickering mode of emulsification. The mechanical properties of polypropylene (PP) and ethylene vinyl acetate copolymer (EVA) were studied after addition of various loadings of these hybrids (2, 4, 8, 12, and 14 wt%). It could be ensured that the tolerance of PP towards phase separation caused by the insertion of the core–shell particles was higher than that of EVA, which translates into different extents of reinforcements. POLYM. ENG. SCI., 55:1546–1552, 2015. © 2015 Society of Plastics Engineers

Synthesis and properties of fluorine–silicon modified polyacrylate hybrid latex particles with core–shell structure obtained via emulsifier‐free emulsion polymerization

AbstractA core–shell fluorine–silicon modified polyacrylate hybrid latex was successfully prepared via emulsifier‐free emulsion polymerization. The chemical composition and core–shell morphology of the resultant hybrid particles were investigated using 1H NMR and Fourier transform infrared spectroscopies and transmission electron microscopy (TEM), respectively. TEM analysis indicated that the core–shell hybrid particles were uniform with narrow size distributions. The particle size and zeta potential decreased with an increase of alkylvinylsulfonate surfactant from 2.5 to 6.0 wt%. X‐ray photoelectron spectroscopy revealed that fluorine concentrated preferentially at the film surface during a film‐formation process. The film formed from the fluorine–silicon modified polyacrylate showed much higher thermal stability than a film formed from polyacrylate and fluorine‐modified polyacrylate. Contact angle results showed that a finished fabric had remarkable water repellency. © 2015 Society of Chemical Industry

Synthesis and properties of Ricinodendron heudelotii oil based hybrid alkyd–acrylate latexes via miniemulsion polymerization

Abstract Ricinodendron heudelotii (R. heudelotii) oil-based novel alkyd–acrylate hybrid latexes were synthesized as waterborne environmental friendly binder for coating systems. Long oil length alkyd resins were synthesized by two-stage alcoholysis–polyesterification reaction with variation of phthalic anhydride (PA) and maleic anhydride (MAH) proportion and further polymerized with methyl methacrylate (MMA) and butyl acrylate (BA) via miniemulsion polymerization. It is found that increasing the proportion of MAH in the alkyd resin enhances monomer conversion and total solid content of the hybrid latex. The latexes exhibited fast drying time at room temperature. The prepared latexes showed a bimodal particle size distribution motion. It is shown that the increase in MAH content in the alkyd moiety has a significant effect on the improved performance properties of hybrid latexes as well as latex films including, fast drying time at room temperature, highly crosslinked network, improved mechanical characteristics before and after UV exposure, better shore A hardness and hydrophobic water repellency contact angle. The results suggested that, the R. heudelotii oil-based alkyd–acrylate hybrid latexes have potential improved properties for manufacture of waterborne coatings and are usable as an alternative to petroleum-based coating systems.

Film forming hybrid acrylic/ZnO latexes with excellent UV absorption capacity

Acrylic/ZnO hybrid latexes were synthesized through a two-step emulsion polymerization process. First, a hybrid seed was synthesized by miniemulsion polymerization, which contained all the hydrophobically modified ZnO nanoparticles. Subsequently, this hybrid seed was employed in a seeded semibatch emulsion copolymerization yielding high solids content hybrid latexes (40wt%). Cryo-transmission electron microscopy (cryo-TEM) demonstrated that the dispersion of the ZnO nanoparticles in the initial miniemulsion was not homogeneous, which led to a hybrid seed with two populations, polymer particles containing ZnO and pristine polymer particles. After the second step of polymerization barely the same morphology was obtained. Nevertheless, it was proved by electron tomography (3D-TEM) that the ZnO nanoparticles were encapsulated in the polymer particles. The hybrid films containing ZnO presented a superior UV absorption capacity than their counterpart hybrid acrylic/CeO2 prepared following the same strategy.