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Organic/inorganic (O/I) composite latexes combine the best attributes of inorganic solids with the processability, lightweight and handling advantages of organic polymers. There are common methods to produce polymer nanocomposites: melt compounding, in-situ polymerization and solution mixing. Emulsion polymerization is an unique chemical process widely used to produce waterborne resins with various colloidal and physicochemical properties. This free radical polymerization process involves emulsification of the relatively hydrophobic monomer in water by an oil-in-water emulsifier, followed by the initiation reaction with a water insoluble initiator. This research focuses on the synthesis and reactions kinetics of polyacrylic latex with the incorporation of various nanospheres (SiO2, TiO2, Al2O3 and Fe2O3), and layered silicate (Bentonite nanoclay) nanoparticles via emulsion polymerization. The influence of nanoparticle concentration on reaction kinetics was also investigated. The results showed that the concentration of nanoparticles has significant influence on the monomer conversion, particle size, coagulum content and viscosity of the emulsion. Furthermore, the nanostructured emulsions were shear thinning, exhibiting a power-law behavior, and the viscosity was influenced by the nanoparticle morphology.

The addition of nanoparticles into polymeric materials has changed dramatically the properties of the host polymers, promising a novel class of composite materials with different properties and added functionalities. This research focuses on the influence of inorganic nanospheres particles such as SiO2, Al2O3, Fe2O3, TiO2 and nanoplatelets, such as Bentonite nanoclay, on the thermo-mechanical properties of a polyacrylic latex (utilized in commercial coatings). The analysis of the thermal and mechanical properties showed a decrease of Young's modulus and glass transition temperature Tg in the presence of spherical nanoparticles. However, there was an increase of these properties in the presence of nanoplatelets (Bentonite), as demonstrated by the dynamic mechanical analysis and uniaxial tensile analysis. Moreover, water contact angle measurements demonstrated significant increase in hydrophobic behavior when incorporating nanosphere particles as compared to nanoplatelets. These results showed that the metallic oxides nanoparticles greatly influenced the physical and mechanical properties of the neat polyacrylic matrix.

Thermosetting polyurethane coating formulations which stratify into two distinct layers after application have been prepared. In a thermosetting system the polymer phase separation among other factors is seen to be kinetically controlled and have less dependence on parameters such as surface tension gradient and polymer solubility. Certain coating applications including those used in architectural, automotive, industrial maintenance and aerospace require a combination of primer/topcoat or basecoat/clearcoat layers. These multilayered systems necessitate complex application and curing procedures. Multiple product formulation, application and processing steps not only require significant amounts of processing time, and contributing to environmental waste generation and pollution they also consume excessive amount of energy and manpower until a solid film has been produced. It would be desirable to reduce the number of layers to a minimum while providing the equal or better overall performance. In this paper we report the design and development of thermosetting polyurethane coatings that self-stratify to two distinct phases upon application and cure. It was demonstrated that kinetically controlled reactions aided by incompatible polymers possessing gradient surface free energies can afford self-stratifying coatings. This investigation also revealed that solvent type, evaporation rate, and gravity did not contribute to stratification of thermosetting coatings. Prototype pigmented systems were applied and cured and characterized by FTIR, SEM/EDX and were evaluated using standard coating test methods. The results of this investigation provide a new understanding of stratification phenomenon and establish that preferentially reactive polymers can be a basis for formulating cross-linkable self-stratifying coatings.

The research on a self-decontaminating surface has received significant attention because of the growth of pathogenic microorganisms on surfaces. In this study, a novel and simple technique for producing an active surface with antimicrobial functionality is demonstrated. A tethering platform was developed by grafting the biocide ampicillin (Amp) to a nanoclay and dispersing the nanoclay in a UV-curable acrylate coating applied on polypropylene films as the substrate. A coupling agent, [3-(glycidyloxy)propyl]trimethoxysilane, was used as a linker between the nanoclay and Amp. The Amp-functionalized clay was further modified with an organic surfactant to improve the compatibility with the coating. Several characterization assays, such as Fourier infrared transform analysis, thermogravimetric analysis, and X-ray diffraction, were conducted to confirm the presence of Amp in the nanoclay. Transmission electron microscopy images revealed that the clay particles were well dispersed in the coating and had a partial exfoliated morphology. The active coating surface was effective in inhibiting the growth of Gram-positive Listeria monocytogenes and Gram-negative Salmonella Typhimurium via contact. These findings suggest the potential for the development of active surfaces with the implementation of nanotechnology to achieve diverse functionalities.

Novel isocyanate-free moisture curepolyurethane coatings with excellent properties have been formulated and evaluated. These coatings utilize polyols derived from the renewable resource soybean oil and its simple derivatives. The coating is autocatalytic and does not require continuous exposure to moisture for the development of full properties. A series of soybean oil-based polyols were synthesized by treating either the raw oil or epoxidized soybean oil (ESO) by a variety of reagents including long chain fatty acids. In a series of model reactions the above polyols were reacted with various diisocyanate compounds, at molar ratio of NCO/OH=1.5:1–3:1 to obtain prepolymers with residual NCO% of around 1.8. The isocyanate-free moisture curable resin was obtained by coapping the prepolymer with of aminosilane followed by the addition of a small amount of methanol. Typical clearcoat formulations become tack-free in less than an hour, recoatable in about one hour, and reach a functional cure stage in 24 hr at 40% RH and 25°C.

Cycloaliphatic epoxy resins are used in coatings and inks because of their exceptionally low viscosity and reactivity with a variety of co-reactants, thus permitting high-solids and zero VOC coatings. The low viscosity of epoxidized soybean oil (ESBO), its reactivity, and relatively low cost make it an inexpensive candidate co-resin in cationic thermally cured coatings and inks using blocked acid catalysts. Formulations with up to 40% ESBO in the epoxy resin blend were investigated. Blending of cycloaliphatic resin with 10% ESBO gave a bake coating with the same results as the standard formulation except pencil hardness was one unit lower when cured for 12 min at 120°C with a heat de-blocked catalyst. The hardness of coatings with ESBO is adjustable by changing the epoxy/polyol ratio, using harder polyols and harder epoxy resins.

Conventional solution polymerization under monomer-starved conditions was compared with separation polymerization, also known as monomer-starved, as a method for making acrylic resins with low polydispersity (D=Mw/Mn). Separation polymerization employs aliphatic or cycloaliphatic solvents that are good solvents for the monomers but poor solvents for the resin; thus, the resin separates during polymerization. Various process conditions, initiators, chaintransfer agents, and solvents were studied, focusing mainly on a monomer line-up of methyl methacrylate, styrene, ethyl acrylate, and 2-hydroxy ethyl methacrylate in a 15/15/40/30 weight ratio. Two initiators, t-amyl peroxy 2-ethyl hexanoate and t-butyl peroxy 2-ethyl hexanoate gave about equal, excellent results. 2-Mercapto ethanol was selected as a chain transfer agent. With these ingredients, the separation polymerization method is capable of producing oligomeric acrylic polyol resins with polydispersities (D) of about 1.7 to 1.8 when Mn is in the range 1350 to 1600. These resins have substantially lower solution viscosities than a commercial benchmark resin, which has Mn=1230 and D=2.03. In preliminary tests of 2K polyurethane coatings, the film properties obtained with acrylics made by separation polymerization were, on balance, superior to those obtained with a commercial benchmark resin.

Publisher Summary Almost all surfaces are coated to enhance substrate properties. Coatings are also used to protect, decorate, and functionalize surfaces. The major advantages of choosing plastics as alternatives to metals are numerous including ease of manufacturing, lower material cost over metal alternatives, corrosion resistance properties and ease of casting, tooling, and styling latitude. Such advantages have led to the increased use of plastics, particularly in the transportation industry, for both interior and exterior applications. A major challenge in coating plastics is the adhesion of various types of coatings. Except for temporary and protective coatings, all other types of surface coatings must adhere tenaciously to the substrates and preferably last as long as the object itself. Since coatings must function by surface attachment only, the nature and condition of the surface is critical to the success of any durable coating venture. In most cases, it is desirable to have a coating that is difficult to remove from the substrate to which it has been applied. An important factor controlling this property is the adhesion between the substrate and the coating. In formulating a coating, it is critical to remember that difficulty in removing a coating can also be strongly affected by how difficult it is to penetrate through the coating and how much force is required to push the coating out of the way as the coating is being removed from the substrate as well as the actual force holding the coating onto the substrate.