Abstract
A hollow core-shell latex particle synthesized through sequential semi-continuous emulsion polymerization method has served as a promising substitute to white inorganic pigments useful for the coating applications. Incorporating more amount of Titanium dioxide in the paint is a costly measure with diminishing returns. Severe paint defects such as phase separation, agglomeration or settling arises due to incompatibility between inorganic pigments and organic resins. Opaque polymer helps in minimizing the cost of Titania in surface coating formulations. It provides white appearance and hiding due to diffraction of incoming light in different directions. It has gained widespread importance over the years due to its unique structure and morphology. It has potential applications in other technologies such as micro-encapsulation, paper coatings and controlled release of drugs. Osmotic swelling – the most prominent approach involves the synthesis of an ionizable core particle which is encapsulated by another polymer functioning as shell, followed by neutralization with the addition of suitable alkali. Significant techniques have been developed including hydrocarbon encapsulation and water-in-oil-in-water emulsion in this field.
Highlights
INTRODUCTION*Energy and material costs are rising for the multibillion-dollar architectural coatings market, yet tough competition between industry leaders prevents passing on increasing manufacturing costs to consumers
A hollow core-shell latex particle synthesized through sequential semi-continuous emulsion polymerization method has served as a promising substitute to white inorganic pigments useful for the coating applications
Almost one third to half of the cost for a typical latex paint is titanium dioxide (TiO2), which is used as a pigment to whiten the coating or increase its opacity
Summary
Energy and material costs are rising for the multibillion-dollar architectural coatings market, yet tough competition between industry leaders prevents passing on increasing manufacturing costs to consumers. The difference of the refractive index between the polymer shell (e.g. npolystyrene =1.46–1.68; nPMMA =1.49) and the (nair =1.0) inside the voids, produces intensive scattering of light, thereby accelerating the intensity of the diffracted light (i.e. diffuse light) and lowering the intensity of the reflected light (i.e. peculiar light) This results in improving the hiding ability of the core-shell particle. The opaque polymer is a non-film forming, water-based emulsion polymer that forms microscopic air voids on drying, as the water diffuses through the polymeric shell These micro voids of fine and narrow particle size distribution behave like a primary pigment, thereby influencing efficient dispersion of TiO2. Compared to simple copolymer/polymer blend, particles with core-shell structure can enhance properties like abrasion resistance, water-resistance, weather-resistance, stain-repellence, anti-radiation performance, tensile strength, impact strength, adhesive strength and remarkably reduce the minimum film forming temperature of the polymer emulsion [7]. Core-shell, hemispherical, or inverted core-shell particles (where polymer at the second step is located at the center and the seed polymer resides at the periphery of the particle) are examples of particle morphologies which can be designed through modification of thermodynamic and kinetic factors
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