![]() ![]() The paint frequently comes as two components which are mixed together just before use: the main paint portion typically consists of an acrylic resin produced by the polymerization of a propenoate ester formed from a polyhydric alcohol (diols and triols). Solvent-borne industrial paints can have a tough protective finish and are widely used in industry as topcoats, for example on car bodies. Mass and viscosity for solution and dispersion polymers.Īcrylic resins may also be used in industrial paints, either as water-borne emulsion paints or as solvent-borne paints. As such they are useful only as dispersions since they would be extremely viscous if they were carried in solution and this would make them unusable.įigure 3 Graph showing relationship between relative molecular The polymers produced by this process typically have relative molecular masses of 500 000 - 1 000 000. The polymers used in these paints are carried in water (water-borne emulsion paints) which as described above are much better for the environment than paints in which the binders are in organic solvents.įigure 2 Water-borne emulsion paints are used as decorative paints, particularly for the inside and outside of buildings (including masonry paints and exterior primers).Įmulsion paints are so-called as they are made by a process known as emulsion polymerization, in which the liquid monomers to be polymerized are first dispersed in water, as an emulsion. Other acrylic esters used as co-monomers with ethenyl ethanoate are ethyl propenoate, butyl propenoates, or a co-polymer of butyl propenoate and methyl 2-methylpropenoate. The binder in many emulsion paints is based on homopolymers or co-polymers of ethenyl ethanoate (vinyl acetate) and a propenoate (acrylic) ester.Įthenyl ethanoate is manufactured by passing a mixture of ethanoic acid vapour, ethene and oxygen over heated palladium(ll) and copper(ll) chlorides:Įthenyl ethanoate and an acrylic ester (for example, methyl 2-methylpropenoate) are then co-polymerized to form a random array, in which these groups link into a linear chain: The three most important binders (resins) used in modern paints are: This unit discusses the most commonly used binders followed by the pigments. Amounts ranging up to 40 000 dm 3 of paint may be made in a single batch.įigure 1 Contents of a white gloss (alkyd) paint and a white matt emulsion (acrylic) paint. Each batch of ingredients is thoroughly mixed in large, stirred containers with the required additives (Figure 1). ![]() Solvent is then added to give the required consistency. The pigment powder is broken down into individual particles which are coated by and dispersed in the binder (resin) - known as 'wetting out'. Paints are formulated according to their proposed use - primer, undercoat, special finishes (matt, gloss, heat resistance, anti-corrosion, abrasion resistance). fungicides and algaecides - to protect exterior paint films against disfigurement from moulds, algae and lichen.bactericides - to preserve water based paints in the can.anti-settling agents - to prevent pigment settling.thixotropic agents - to give paints a jelly-like consistency that breaks down to a liquid when stirred or when a brush is dipped into it.silicones - to improve weather resistance.dispersants - to separate and stabilise pigment particles.The binder may be dissolved as a solution or carried as a dispersion of microscopically small particles in a liquid.ĭepending on the type of paint and intended use, additives may include: The binder (resin) and solvent together are sometimes known as the vehicle. additives - used to modify the properties of the liquid paint or dry film. ![]() Water-borne paints are replacing some paints that use volatile organic compounds such as the hydrocarbons which are harmful to the atmosphere. solvent (sometimes called a thinner) - either an organic solvent or water is used to reduce the viscosity of the paint for better application.extender - larger pigment particles added to improve adhesion, strengthen the film and save binder. ![]() binder (resin) - a polymer, often referred to as resin, forming a matrix to hold the pigment in place.pigment(s) - prime pigments to impart colour and opacity.Paints may be broadly classified into Decorative paints, applied on site to decorate and protect buildings and other objects, and Industrial coatings which are applied in factories to finish manufactured goods such as cars. Paint is used to decorate, protect and prolong the life of natural and synthetic materials, and acts as a barrier against environmental conditions. ![]()
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