IMF and Industry News

Abstract

The Organic Finishing Group of the IMF is dedicated to supporting and promoting the interests of the paint and powder coating sector for metal finishing. We meet regularly to discuss topics of importance and relevance, from coating manufacture through application to final testing and specification. What does ‘Organic’ mean? In the context of materials finishing, it is any finish which is based on organic chemistry as opposed to electroplating, which is generally inorganic – the application of a metal to a surface. Organic chemistry is based on compounds made up of carbon, hydrogen and oxygen starting with the simplest CH4 – methane – and building up with the addition of carbon and hydrogen atoms to multiple carbon chain polymers, to which can be added oxygen and nitrogen. The most common example of organic surface finishing is paint. Functional Groups in polymers and monomers used in paint include amines, carboxylic acids, amides, alcohols, esters, isocyanates and carbamates (urethane). The use of the words, paint and coating, can be used interchangeably – they mean the same thing. However, it is necessary to distinguish between a coating system and a coat of paint. A coating system is more than just the material applied, it also refers to other factors such as the surface preparation requirements, the application of a number of coats of paint, in a specific order, and the thickness of each coat of paint. A coat of paint is a single layer, applied to form a coherent film when dry. All liquid paints are composed of three basic ingredients: resins (polymers), pigments and solvent. The resin is the film-forming portion of the paint it holds together the pigment particles and binds the paint to the surface. The resin plays the main part in contributing to the durability, strength and chemical resistance of the final film. Paint types are often referred to by the type of resin in the formulation, so when we talk about an alkyd or epoxy, for example, we are referring to the main resin used to make the paint. The second ingredient in paint is the pigment. This is a relatively insoluble finely divided powder, or more commonly a mixture of powders. The pigment(s) primarily provide hiding power (opacity), and colour, but they also improve weather resistance, increase paint adhesion, decrease moisture permeability and control gloss. The final ingredient, the solvent, ‘carries’ the resin and pigment(s) and controls the viscosity such that the paint can be applied to a surface. The chemical ingredients in each of the components vary widely from one generic type of paint to another, in addition, each of the components (resin, pigment and solvent) are also usually mixtures of different materials. For example, a paint formulation may contain three or four solvents one solvent dissolves the resin, while some are used to control evaporation, and others are used to dilute the solution (control viscosity). It is not important for a user to know all the ingredients in paint, suffice that he knows the properties. The common designation of a series of coatings applied to a surface is primer, intermediate or build coat, and top coat. Normally each coat contains properties that contribute to the success of the total coating system.