Coating application has two wings, one is PAINT other is INK.
Sometimes we get confused, between Paint and Printing inks. Both are coatings, But application wise, they have differences. Paint is known as the Coating For decorative and protective purpose. Printing ink is also coating but in Graphic-Way, where decoration is more important as Substrate, takes care of protection. Very simply, both are the selection of Raw-Materials, depending on the purpose. Subjects are Application and Selection. There are so many common raw-materials used in Inks and Paints.
General-Properties - Naturally and Physically
Printing-inks are generally in two Forms, Paste-Form and Liquid-Form ( off-set inks and screen inks are in paste form, means more viscous than gravure and flexo-inks. It is in general way only). In Roto-Printing process the flow (viscosity) of the inks must be low (as printing-process's demand) for both the Inks.
But visually, physically and application-way, Paint is always in Liquid-Form.
Drying-Process (curing) - oxidation, evaporation (solvent-release), radiation-cure.
It occurs, when oxygen molecules from air initiate on the surface of coating, to make the surface dry. When in formulation, plant-oils are used as one of the main ingredient, for in both enamel-oil-bound paints and oil-bound-inks (off-set, rotary-news-inks, screen inks). This type of drying occurs mainly where the surface is non absorbent. Adding Driers(metal-carboxylates) we accelerate the drying-process.
Evaporation-Drying( solvent –release-way)
It occurs mainly, where solvents take major-part in formulation. Solvent releases from the surface of the coating, by the process of evaporation to make the surface dry and cure. This type of drying is faster than, oxidation-drying. And also it depends on the nature of solvents used in formulation. This type of drying occurs for both absorbent and non-absorbent surfaces.
Photo-energy(light)initiates, on the surface of the coatings and cures the surface, with the help of photo-initiator. It is faster than oxidation-drying but slower than evaporation–solvent-release drying. Here surfaces may be absorbent and non-absorbent.
It is the section of formulation mainly, although it looks like a Physical, Visual part of the coating ( both Inks and Paints) but selection of pigments is very important for the purpose (end-use) of the Coatings.
The binder holds the coating-system with surface. It is also the section of formulation. It has so many roles in coating, application, finishing and others too, for both Inks and Paints applications.
It adds, always some-thing-special to both Inks and Paints, in today's demand-wise-technology additives have great role, from Processing to Finishing and for the purpose of end-use.
Apurba Krishna Das