Coating knowledge: main compositions and function of emulsion paint

a)Base stock (film former) : synthetic resin emulsion (styrene-acrylic, acetic styrene-acrylic, acrylic latex, silicone acrylic, etc.). Function: emulsion is non-volatile part of the coating, also known as binding material, it is the foundation of the film, it can make pigments and fillers bonding together and adhere to the content on the film. The grade of the coating and performance level mainly decided by film former.

b)Pigment: titanium dioxide, zinc oxide, lithopone (BaSO4. ZnS) and other pigments. Function: it is a micro powder coloured material. It does not dissolve in water or oil base, but can evenly disperse in media to form even suspensoid. The object distributed on surface of coating to give the film covering power and color.

c)Filler: CaCO3 (light and heavy), talcum powder, kaolin, etc. Function: a physical pigment, which is white powder and mostly do not have covering power and tinting strength, the price is low. It can add the film’s thickness, improve the durability, wear resistance and other mechanical strength, also can reduce the cost of coating.

d)Solvent: to dissolve and diluted paint film former, it also can reduce the viscosity of the coating. But after film formation it will still remain in the film. It is a kind of volatile matter (solvent of emulsion paint is water, which is cheap, vast, non-toxic)

e)Additives: dispersant, wetting agents, thickening agents, film additives, mildew preventive, etc. Function: to increase coating processing properties, construction performance, storage performance and coating properties.

i.Dispersant, wetting agent: be good for scattering of pigments and fillers. Wetting agent influence the affinity of the basic level of coating, and leveling property.

ii.Film additives: decrease coating temperature, be benificial to film forming in cold weather and good to improve the film performance.

iii.Defoaming agent: defoaming, convenience in machining process and the defoaming during construction process

iv.Mildew preventive: to prevent the coating’s reeking and film’s mildewing in damp environment.

v.Thickener: usually have 3 types: hydroxyl cellulose, alkali soluble type and associating type.

By Nicole