Industrial chemistry paint ppt

NOTES: industrial chemistry notes for B.Sc. Chemistry students

1. INDUSTRIAL CHEMISTRY Paint, pigment and varnishes U.HAJARA BANU M.Sc., B.Ed., Assistant Professor of chemistry

2. PAINT Definition Classification of paint Constituents of paints Requisites of a good paint CONTENT

3. DEFINITION: P aint is a mechanical dispersion of one or more pigment in medium (liquid, non-volatile) drying oil and thinner. When a metallic surface is painted, the thinner evaporates while the drying oil forms a dry pigmented film after oxidizing itself . PAINT

4. 1.Emulsion paints E mulsion paint is a dispersion of rubber like resin in water. It contains film forming vehicle, pigmentation and extender. The main constituent of emulsion paint is stabilizer, drier and antifoaming agent. Emulsion paints provide Easy to apply on surface of metal or wood. Quick drying. More durable. More impermeable to dust and dirt. 2. LUMINESCENT PAINT I t contains luminor pigment which fluoresce under influence of UV light. Such pigment absorb UV and emit radiation in the visible region of the spectrum. EX: ZnS , sulphides of Zn, titania with a small amount of colour modifiers like Cu, Ag, Mn and B called activators. CLASSIFICATION OF PAINTS:

5. 3.HEAT RESISTANT PAINT: Heat resistant paint are paints that withstand temperatures, even up to red heat It is suitable for space technology. Composition: TiO 2 (pigment),Water solution of an alkali metal silicates(vehicle), aluminium orthophosphate (wetting agent), and water (thinner). USES: It is used as finishes of ovens, furnaces, oil stills, air craft combustion chambers, diesel-engine exhaust pipes, smoke stacks. 4.DISTEMPERS: Distempers are water paint Ingredient : chalk powder(base), glue(blinder), colouring pigments and water. USES: It is used as finishing coat on White washed surface of interior walls. Plastered surfaces of interior walls External surfaces of brick-works, concrete.

6. 5. Water repellent paints: Water repellent paints are made by hydrolysis and condensation of organoethoxy silianes and organochloro silans It is more durable It can last for more than 5 years 6. COAL TAR PAINTS: It consists of a melt of coal tar and spirit is applied on the surface at the hot condition USES: it is used for protecting iron and steel surfaces and materials used under the ground

7. 7.ANTIFOULING PAINTS: It is a special coating that is applied to marine crafts Antifouling agent: mercuric oxide, cuprous oxide etc., USES: it is used in marine construction It retards the fouling of ship piers by marine worm, fungi etc. It is used for controlling the corrosion.

8. 1.PIGMENT Pigments are various inorganic and organic insoluble substances, which are of different colours depending upon the composition It is used for surface coating EXAMPLE White pigment – Zinc oxide, white lead, titanium dioxide Red pigment – red lead, ferric oxide, chrome red Green pigment – chromium oxide Black pigment – carbon black Pigment provide strength to paint Protection to the film by reflecting harmful ultraviolet Resistance against wear Impermeability to moisture Aesthetic appeal to the paint film A good pigment should be Opaque, chemically inert, non toxic Cheap Freely mixable with film foaming constituent oils CONSTITUENTS OF PAINT

9. 2.EXTENDERS OR FILLERS It reduces the cost and increase the durability of the paint. It improve consistency, leveling and setting of paint. They serve to fill voids in the film and act as carrier for pigment colour Ex: Barite (BaSO 4 ), talc, asbestos, gypsum(CaSO 4 ). 3.Drying or film forming materials Drying oil oils is also called vehicle. They are glycerides of higher fatty acids. It may be vegetable oil. It absorbs oxygen and forms peroxides hydro peroxides etc. They provide toughness durability, adhesion and water proofers to the film.

10. 4.DRIERS: Its accelerate the drying of the film through oxidation and polymerization process. EX: PbO , modern driers are Co, Mn , Pb , Zn, resinaleate , linoleate and naphthalenates . 5.THINNER: It is a highly volatile liquid. It reduces viscosity of the paint and increase its elasticity. It increases the penetration power of drying oil. The common thinner is turpentine oil. Other thinners are benzene, mineral sprit, xylol , kerosene, etc

11. 6.PLASTICISERS It is used to increase elasticity and to minimize cracking EX: dibutyl phosphate, tricresyl phosphate, dibutyl tartarate etc.. 7. ANTI SKINNING AGENTS It prevent skinning and gelling of paint film EX: polyhydroxyphenols

12. Requirements or characteristics of good paint A good paint has the following qualities It should be opaque and chemically inert. It should have high covering power. It should for, a tough, uniform and adherent film. The coating of paint should not crack after drying. It should be non toxic, stable and long life. It should neither be oxidized nor reduced in environment. The colour due to paint should be shinning and stable. Various requirements of paint are controlled by pigment volume concentration(PVC) which is defined as PVC= (volume of pigment in the paint/total volume of the constituent)× 100 The PVC range of various paints are Flat paint – 50-75% Exterior house paint -28-36% Metal primers – 25-40% Wood primers – 35-40%

13. TIME FOR QUESTION

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