ashish paints

8/22/2019 ashish paints

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PAINT Paint is any liquid, liquefiable, or mastic composition

which after application to a substrate in a thin layer isconverted to an opaque solid film.

Paint is used toprotect, preserve,decorate, or add functionalityto an objector surface by covering it with a pigmented coating.

An example of protection is to retardcorrosion of metal. An example ofdecoration is to add festive trim to a room's interior.

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Despite the fact that there are many different types ofhouse paint, most fall into one of two categories: oiland water. Oil based house paint is referred to as

alkyd, while water based house paint is commonlycalled latex or acrylic . The main differences betweenthe two are their drying processes, their finishes, andthe ease or difficulty of clean up. Oil based house painttakes longer to dry than the water based variety, but itcontains additives to help speed up the drying process.Oil paints also create a harder, glossier finish, andrequire paint thinner or other chemicals for clean up.Water based paints, on the other hand, dry quickly as

moisture evaporates. Their finish is not as shiny or asdurable, but the ease of clean up makes water basedpaints a popular choice. They can be cleaned up withwarm water and a bit of mild detergent.

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An example of addedfunctionality is to modify

light reflection or heatradiation of a surface.Another example offunctionality is the use ofcolour to identify

hazards or to identify thefunction of equipment andpipelines.

Paint can be applied toalmost any kind of object. Itis used, among many other

uses, in the production of art,in industrial coating, as adriving aid (road surfacemarking), or as a barrier toprevent corrosion or waterdamage.

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Paint is a semi finishedproduct, or intermediategood as the final product isthe painted article itself.

Paint can also be mixedwith glaze to create varioustextures and patterns. Thisprocess is referred to asfaux finish and isquite popular withdiscerning homeowners,architects and interiordesigners.

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Composition of CoatingsMost coatings have four basic types of ingredients:

PigmentBinder

Vehicle or solvent

Additives

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Pigments

Pigments are granular solids incorporated into the paint to contributecolour, toughness or simply to reduce the cost of the paint.

Alternatively, some paints contain dyes instead of or in combination withpigments. Other paints contain no pigment at all.

Pigments can be classified as either natural or synthetic types.

Natural pigments include various clays, calcium carbanate , mica,silicas, and talcs.

Synthetic pigmentswould include engineered molecules, calcined clays, ,precipitated calcium carbonate, and synthetic silicas.

Hiding pigments, in making paint opaque, also protect the substrate fromthe harmful effects of ultraviolet light. Hiding pigments include titaniumdioxide, phthalo blue, red iron oxide, and many others.

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Fillers

Fillers are a special type of pigment that serve to

thicken the film, support its structure and simplyincrease the volume of the paint.

Fillers are usually comprised ofcheap and inertmaterials, such as talc, lime, baryte, clay, etc.

Floor paints that will be subjected to abrasion may evencontain fine quartz sand as a filler.

Not all paints include fillers.

On the other hand some paints contain very largeproportions of pigment/filler and binder..

Some pigments are toxic, such as the lead pigments thatare used in lead paint. Paint manufacturers beganreplacing white lead pigments with the less toxicsubstitute, which can even be used to colour food, titanium

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Binder

The binder, or resin, is the actual film forming componentof paint.

It is the only component that must be present; othercomponents listed below are included optionally,depending on the desired properties of the cured film.

The binder imparts adhesion, binds the pigmentstogether, and strongly influences such properties as

gloss potential,

exterior durability,

flexibility,

and toughness. Binders include synthetic or natural resins such as acrylics,

polyurethanes, polyesters, melamine resins, epoxy, or oils. 9


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Binders can be categorized according to drying, or curingmechanism. The four most common are simple solventevaporation, oxidative crosslinking, catalyzedpolymerization, and coalescence. There are others.

Note that drying and curing are two different processes.

Drying generally refers to evaporation of vehicle,whereas curing refers to polymerization of the binder.Depending on chemistry and composition, any particularpaint may undergo either, or both processes. Thus, there arepaints that dry only, those that dry then cure, and those thatdo not depend on drying for curing.

Paints that dry by simple solvent evaporation contain a solid

binder dissolved in a solvent; this forms a solid film whenthe solvent evaporates, and the film can re-dissolve in thesolvent again.

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Latex paint is a water-based dispersion of sub-micrometre polymer particles. The term "latex" in thecontext of paint simply means an aqueous dispersion;

latex rubber (the sap of the rubber tree that hashistorically been called latex) is not an ingredient.These dispersions are prepared by emulsionpolymerization.

Latex paints cure by a process called coalescencewhere first the water, and then the trace, or coalescing,solvent, evaporate and draw together and soften thelatex binder particles and fuse them together into

irreversibly bound networked structures, so that thepaint will not redissolve in the solvent/water thatoriginally carried it.

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Paints that cure by oxidative crosslinking are generallysingle package coatings that when applied, the exposure tooxygen in the air starts a process that crosslinks and

polymerizes the binder component. Classic alkyd enamelswould fall into this category.

Paints that cure bycatalyzed polymerization aregenerally two package coatings that polymerize by way of achemical reaction initiated by mixing resin and hardener,

and which cure by forming a hard plastic structure.Depending on composition they may need to dry first, byevaporation of solvent. Classic two package epoxies orpolyurethanes would fall into this category.

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Still other films are formed by cooling of the binder.For example, encaustic or wax paints are liquid whenwarm, and harden upon cooling. In many cases, theywill resoften or liquify if reheated.

Recent environmental requirements restrict the use ofVolatile Organic Compounds (VOCs, and alternative

means of curing have been developed, particularly forindustrial purposes. In UV curing paints, the solvent isevaporated first, and hardening is then initiated byultraviolet light.

In powder coatings there is little or no solvent, andflow and cure are produced by heating of thesubstrate after application of the dry powder.

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Vehicle or solvent The main purpose of the vehicle is to adjust the

viscosity of the paint. It is volatile and does notbecome part of the paint film. It can also control flowand application properties, and affect the stability ofthe paint while in liquid state. Its main function is as

the carrier for the non volatile components. Volatilesubstances impart their properties temporarilyoncethe solvent has evaporated or disintegrated, theremaining paint is fixed to the surface.

What is viscosity? - In everyday terms (and for fluidsonly), viscosity is "thickness".

Thus,water is "thin", having a lower viscosity, whilehoneyis "thick" having a higher viscosity.

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http://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Honeyhttp://en.wikipedia.org/wiki/Honeyhttp://en.wikipedia.org/wiki/Water


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Water is the mainvehicle for water-based paints.

Solvent-based, sometimes called oil-based, paints canhave various combinations of solvents as the vehicle,including aliphatics, aromatics, alcohols, and ketones.

These include organic solvents such as petroleudistillate, esters, glycol ethers, and the like.

Sometimes volatile low-molecular weight syntheticresins also serve as diluents. Such solvents are usedwhen water resistance, grease resistance, or similarproperties are desired.

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Besides the three main categories of ingredients, paint canhave a wide variety of miscellaneous additives, which are

usually added in very small amounts and yet give a verysignificant effect on the product. Some examples includeadditives to

Modify surface tension, Improve flow properties, Improve the finished appearance, Increase wet edge, Improve pigment stability, Impart antifreeze properties, Control foaming, Control skinning, etc. Other types of additives include catalysts, thickeners,

stabilizers, emulsifiers, texturizers, adhesion promoters,UV stabilizers, flatteners (de-glossing agents), biocides tofight bacterial growth, and the like.

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Semi Gloss Enamels These do not have much film former but a higher

percentage of pigmentation than gloss enamels. The

pigment particles are designed to project through thesurface to diffuse the light refraction to achieve a lowersheenPaints comes in a variety of finish gloss levels. These arenot standardized, but normally run:

flat matte eggshell satin semi-gloss high gloss

Different manufacturers group these differently, so someconsider flat and matte to be synonymous, and so on.

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Manufacturers describe finish by percent gloss, where0% gloss is a dull unreflective surface and 100% gloss is

mirror-like. Values for percent gloss vary, as do the terms. For

example, one manufacturer lists the values as such:

Flat (1-9% gloss)

Low Sheen (10-25% gloss)

Eggshell (26-40% gloss)

Semi Gloss (41-69% gloss) Gloss (70-89% gloss)

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Relative durability of finishes:

Since the material they use to create gloss is dense andglassy, a gloss paint will be more resistant todamage than a flat paint.

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Ease of cleaning: Glossy surfaces do not trap dirt like flat finishes, and

generally are easier to clean. High-gloss paint is also

more resistant to staining.

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Ease of repair/touchup: Flat can be touched up locally without repainting the

entire surface.

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Other considerations:

Prep time for high gloss surfaces is considerably morethan for flat.

The gloss finish will reveal surface imperfectionssuch as sanding marks and fingerprints. In the

automotive and marine industry, this is a majorconsideration.

In traditional household interiors, walls are usuallypainted in flat or eggshell gloss, wooden trim

(including doors and window sash) in high gloss, andceilings almost invariably in flat. Similarly, exteriortrim is usually painted with a gloss paint, while thebody of the house is painted in a lower gloss.

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Acrylic paint is fast-drying paint containing pigmentsuspended in an acrylic polymer emulsion.

Acrylic paints can be dilutedwith water, but becomewater-resistant when dry.

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Enamel paint is used to describe oil-based coveringproducts, usually with a significant amount of gloss inthem, however recently many latex or water-based

paints have adopted the term as well.

The term today means "hard surfaced paint" andusually is in reference to paint brands of higher quality,floor coatings of a high gloss finish, or spray paints.

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Sealers , Primers and Undercoats These are paints used to prepare the surface for

painting. The sealer is used to seal the surface tominimise porosity while the primer is used to facilitate

both adhesion and ease of application of the topcoat.

The term undercoat is often confused with the primercoat although the two are quite different. Theundercoat is used to cover the primer or sealer and actas the base colour for the coats of paint.

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Color changing paint

Various technologies exist for making paints thatchange color.

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Thermochromic paints

Thermochromic paints

and coatings containmaterials that changeconformation when heat isapplied, and so theychange color.

Liquid crystals have beenused in such paints, suchas in the thermometerstrips and tapes used infishtanks.

Recently car manufactureshave been testingThermochromic paints ontheir products.

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Photochromic paints


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Photochromic paints

Photochromic paints

and coatings containdyes that changeconformation when thefilm is exposed to UV

light, and so they changecolor.

These materials are usedto make eyeglasses.

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Electrochromic paints

Electrochromic paints

change color in responseto an applied electriccurrent. Carmanufacturer Nissan

has been reportedlyworking on anelectrochromic paint foruse in its vehicles, basedon particles ofparamagnetic iron oxide.

See pic opposite

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Electrochromic paints can be applied to plasticsubstrates as well, using a different coating chemistry.

The technology involves using special dyes that changeconformation when an electric current is appliedacross the film itself.

Recently, this new technology has been used toachieve glare protection at the touch of a button inpassenger airplane windows.

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Common Paint Film Problems/Defects

Mildew occurs inmoist humid conditions( bathrooms, kitchens,

laundry rooms) whenusing alkyd or oil basedpaint or lower qualitypaint. Can occur due tofailure to prime woodbefore painting and notsuccessfully removingmildew from the surfacebefore repainting

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Cracking and Peeling

-occurs if the paint had

inadequate adhesion andflexibility, overspreadingor thinning of the paint,inadequate surface

preparation or applyingto bare wood withoutprimer, and hardeningand fragility as the paint

ages.

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Bleeding -Discolouration of paint

film due to pigmentseeping to the surface

from undercoats or gumfrom knots in timber.

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Blistering

-formation of small areasofswelling on thesurface caused bypainting in the direct

heat of the sun or fromtrapped moisture,seeping through to thesurface or from corrosion

sites.

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Chalking

-appearance offinepowder on the paintfilm due to weathering

causing the resin tobreak down, or paintingover a porous surface.

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Cissing

Shrinkage or contractionof the new coating awayfrom area which is

contaminated by grease, oilor polish ( particularlysilicone types.)

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Crazing

- irregular cracking ofsurface film due to ageapplication of the paint

over an oily or wetundercoat.

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Efflorescence

- formation of a series ofopen blisters in a paintfilm due to soluble salts

rising to the surface frombrick, plaster andcement objects.

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Flaking

- occurs when the paintpeels away from thesurface due to a crack or

joint in the film. It maybe caused by use of anunsuitable undercoat, orshrinkage/ expansion of

the surface.

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Sagging

- Formation of a waterfall

like appearance on thesurface due to , too muchpaint being applie in onecoat.

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