Evaporation Of Latex Paint

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This report deals with the drying of paint, with the main focus on latex paint. Evaporation and polymerisation are the two main processes in drying paint. These are described and the effects that the environment has on evaporation is discussed. Furthermore, an attempt was made to create a theoretical model to predict the evaporation of paint and an experiment was carried out to test this model. Several plates were prepared with different mixtures and two were coated in paint. The experimental data of the evaporation of water agrees with the theoretical model. The drying of the latex paint however, does not coincide with the theoretical model.
INTRODUCTION
In this project we take a look at the drying process of paint. At first this may not seem …show more content…

Water is a commonly used solvent, because it is more environmental friendly and healthier than organic solvents. In water based paints there are usually organic co-solvents present to help the film forming process.
In oil-based paint, the solvent is a mixture of organic substances, wherein toluene or xylene are usually the largest components (> 50%). In addition, a whole range of other organic compounds are used, which are usually ketones or alcohols[1][2].
Paint often contains a colouring material and that is either a pigment or a dye. The main difference between these is that a pigment is insoluble and a dye is either a liquid or soluble in the paint. Acrylic paints contain only pigments, so dyes will not be discussed further.
Pigments are used since ancient times and are originally extracted from plants, animals or minerals, but today most pigments are synthetic. The biggest disadvantage of using pigments is that they are insoluble in water and do not attach to the surface the paint is applied on. To overcome this, manufacturers use different additives in their paints to keep the pigment in suspension and improve dispersion. In order to attach the pigment to the surface, the binding agent is …show more content…

In physical drying, no chemical reaction takes place. The binding agent’s long polymers have been dissolved in a solvent. During drying, the solvent evaporates and the long polymer chains remain unaltered as a film. Some paints dry only by means of evaporation of the solvent, but the majority of paints dry chemically[1].
Chemical drying is usually slower. This is because in addition to the evaporation of the paint’s solvent, there is also a chemical reaction that takes place. In this reaction polymers form which provide the binding in the paint’s film. In most cases organic molecules crosslink themselves through oxidation reactions to form a polymer network of large macromolecules. The energy required for this chemical oxidation process is often provided by ultraviolet light[1][3].
The less ventilation and amount of light, the slower this type of paint generally will dry. To accelerate this process, a catalyst is usually added. Paints which dry by means of oxidative crosslinking are catalysed by metal compounds such as cobalt naphtenate[1].
There are also coatings which consist of two different components, a base and a hardener. These paints do not dry by means of oxidation with the air, but by a polymerization reaction between the two

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