Bld62003 mak paint
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Transcript of Bld62003 mak paint
What is paint?
Paint is more than just the color; it is a material that is applied as a liquid and dries by a variety of chemical processes to a solid state.
Purpose of paint:
1. Decoration
2. Protection
3. Identification
4. Sanitation MAK/BLD62003/PAINT 2
BINDERS The binder exists to hold the pigment to the surface.
The binder is a polymeric substance, and is either dissolved in the paint or suspended in it by emulsifiers.
Harden to produce paint film
Natural linseed oil – set by oxidation on exposure to air
Bind pigments together
Gives adhesion to surface
Provide resistance to water, chemical & abrasion
Determines performance and resistance characteristics of a paint
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• Natural oils that polymerize as they dry. • Take longer time to dry & have variable properties as the
balance of oils varies from crop to crop. Drying oils
• Most common resins to be used in solvent-based paints. • They are usually polyesters & used for both air-drying & heat-
cured paints. Alkyd resins
• These are emulsions in water and are the most common water-based binders for use in household paint.
Vinyl & acrylic emulsions
• These resins are based on polymers containing the simple
organic compound oxirane (ethylene oxide). • A variety of other components are added to give a wide
range of properties.
Epoxy resins
• Polyurethanes are polymers of any ester of carbamic acid,
H2N—CO2H. • Polyurethane-based paints are tough, durable films that
retain their gloss and are easy to clean. Often used for painting aircraft
Polyurethanes
SOLVENT: To act as a carrier for the pigments and resin
For emulsion paints the solvent is simply water, and for resin-based paints a variety of organic compounds are used with the most common being mineral turpentine.
Water or organic : hydrocarbons, ketones or esters
Same effect with thinner
Ease the application of paint
Evaporate completely once coating has been applied
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BASE
Usually white titanium dioxide
Produces the required opacity/ solidity
EXTENDER
Increase the opacity
E.g silica, calcium carbonate
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DRIER/ RESIN The binder to hold the pigment particles together
Provide adhesion to the surface painted
Induces polymerization of binder
Ensures a rapid drying process
Waterborne paints most often use acrylic emulsion polymers as binders.
Common acrylic polymer types are based on monomers such as methyl methacrylate and butyl methacrylate.
Traditionally, lower cost paints have been formulated on PVA (Poly Vinyl Acetate) binders.
Solvent-based resins come in a very wide range of types. The most common solvent-based resins are termed ‘alkyd resins’ that are normally used in enamel paints.
Urethane alkyds often used in clear varnishes. Protective coating resins include types such as Epoxy, Urethane, Polysiloxane and Moisture Cured Urethane.
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PIGMENT To provide color & finish, hiding & control gloss
To protect the surface underneath from corrosion and weathering as well as helping to hold the paint together.
Both inorganic and organic substances are used, with the inorganic ones being in general cheaper but less clear colors.
Special pigments can be used to give metallic finishes (for car bodies), to be hard wearing (for road markings) etc.
Pigments are divided into two groups: 1. ‘Prime Pigments’ : Titanium Dioxide (white), Chrome Green Oxide, Yellow
and Red Iron Oxides, etc.
2. ‘Extender Pigments’ : Calcite (Calcium Carbonate), Talc (Magnesium Silicate), Mica, Barytes (Barium Sulphate), etc.
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Additives
To enhance certain properties such as ease of brushing, mould resistant, scuff resistance, drying & sag resistance.
Low-odorless additives
Low solvent additives
Gives paint its smooth texture, driers, anti-settling agents, anti-skinning agents a& a host of others that enable paint to cover well & last long
Enhance performance
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• Finely grounded minerals to provide extra volume to paint, reduce cost & make paint easier to be applied.
Extender
• Speed up dry process Drier, hardener,
catalyst
• Jelly like structure added to paint to provide a non drip paint & allow more paint to be held by brusher or roller
Gelling
• Improves stability of paint against organic growth e.g fungi or algae Fungicides
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Water borne paint
• Soluble in water
• Applied in emulsion paint
• Less environment pollution, health & fire hazard
Solvent borne paint
• Soluble in liquid other than water
• Applied in enamel paint
• Provides glossy appearance
Acrylic base paint
• Water based
• Odorless
• Quick drying
• Durable & easy to use
Alkyd based paint
• Resin, oil modified
• Dry faster and harder than oil paint
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PRIMER
Substance that adheres well to substrate
Protects the material Offer a good base for the
undercoat Promotes adhesion Prevents absorption of
later coats by porous surfaces
Gives corrosion resistance over metal
UNDERCOAT
Ensures a good even color Provides good base for
finishing coat Provide a fresh surface of
uniform texture & color close to the finishing coat
Imparts opacity to the total paint system
Levels out minor irregularity
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SEALER
Prevents migration of substances from substrate into later coats
FINISHING COAT
Durable and decorative surface
Determines visible gloss & texture of surface
Maybe resistance to chemical & weather
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Most non-texture paint coatings are approximately 0.2mm – 0.4mm thick for coat (dry thickness)
Enough time must be allowed for drying each coat before applying the next coat
Prevent coats from mixing together
Excessively thick coats can result in sagging of paint or uneven drying
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WALL
Painted with different non glossy colors
Doors and window frames sometimes are painted but can be either glossy or non-glossy
Purpose: aesthetic value & the quality of wall surface is maintain & last longer
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CEILING
Usually non glossy
The designs are drawn according to different cultures
There are also ceiling paint in plain color
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STEEL BARS
Bars made of steel are usually painted
To prevent steel from rusting easily
Paint used are usually glossy
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PAINT
(types)
Multicolor
Broken color
Acrylated rubber
Heat resisting
Flame retardant
Intumescent coatings
Fungicide
Enamel
Micaceous iron oxide
Masonry
Waterproofing
Epoxy
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MULTICOLOR
Incorporates flecks Gives a hardwearing
graffiti removal through spray gun
Can be adjusted to change pattern & texture of the fleck
Applied to dust & grease-free internal surface
BROKEN COLOR
Reflects traditional processes of graining, stippling.
Requires a base coat with clear colored glaze
Pattern the glaze to create desired effects e.g. metallic, shimmer, etc.
Odor free Dry within 2 hours
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ACRYLATED RUBBER
For chemical exposure attach or wet & humid atmospheric conditions
Non environmentally damaging
Applied to metal or masonry by brushing or spraying
HEAT RESISTING
Aluminum paint Lustrous metallic finish Resistant to 230 – 260
degree Celsius The most satisfactorily is
100 degree Celsius
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FLAME RETARDANT
Emit non-combustible gases when subject to fire
Consists of antimony oxide Applied to plywood and
particleboard E.g. matt, semi-gloss and
gloss Applied by brush, roller or
spray
INTUMESCENT COATINGS
Thin film 1mm – 2mm Fire protection to structural
steel without visual effect Expands up to 50 times to
form a layer of insulating form when exposed to fire
30, 60 or 120 minutes fore protection
Applied for timber
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FUNGICIDE
For mould growth
ENAMEL
Highly durable Impact resistance Easily cleaned Hard floss surface For machinery & plant
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MICACEOUS IRON OXIDE
Resistant to moisture on structural steelwork, iron railing
Mica plates reduces permeability to moisture vapor
Applied over metal primer
MASONRY
Smooth and sand texture Suitable for brick, block,
concrete, stone & rendering Hides fine cracks through sand
textured materials Contains fungicides to prevent
discoloration by moulds and algae
Water based Fast drying Forms a crystalline protective
layer over masonry
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WATER REPELLENT & WATERPROOFING
Made of silicone Prevent damp penetration E.g. bituminous, epoxy etc
EPOXY
Highly resistant to abrasion and spillages of oils, detergents or dilute aqueous chemicals
Finishes top concrete, stone, metal & wood
Requires mixing immediately before applications
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MASONRY WALL & CEMENT SUBSTRATES
Allow plaster to adequately dry
Apply 1 coat of alkali resistant sealer
1 undercoat 1 finishing coat
WOOD SUBSTRATES
Sanding, filling up gaps on fully seasoned wood
Apply 1 coat of aluminum wood primer
1 undercoat 1-2 finishing coat
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Gives good protection to all kind of masonry surfaces from ultraviolet rays present in sunrays.
Good protection from severe climatic conditions i.e. rain, heat, water, humidity, salt atmosphere.
Prevents growth of fungus and bacteria on masonry surfaces.
Hides out irregularities, hair lining, roughness etc. thus giving smooth & pleasing appearance to all cemented masonry surfaces.
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PROCESS:
Making the paste Dispersing the
pigment Thinning the paste Canning the paint
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Dilution This usually occurs when the dilution of the paint is not done as per
manufacturers recommendation. There can be a case of over dilution and under dilution, as well as dilution with the incorrect diluent.
Contamination Foreign contaminants added without the manufacturers consent can cause
various film defects.
Peeling/Blistering Most commonly due to improper surface treatment before application
and inherent moisture/dampness being present in the substrate.
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Chalking Chalking is the progressive powdering of the paint film on the painted
surface.
The primary reason for the problem is polymer degradation of the paint matrix due to exposure of UV radiation in sunshine and condensation from dew.
The degree of chalking varies as epoxies react quickly while acrylics and polyurethanes can remain unchanged for long periods.
Cracking Cracking of paint film is due to the unequal expansion or contraction of
paint coats.
It usually happens when the coats of the paint are not allowed to cure/dry completely before the next coat is applied.
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Erosion
Erosion is very quick chalking. It occurs due to external agents like air, water etc.
Blistering
Blistering is due to improper surface exposure of paint to strong sunshine.
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http://www.resene.co.nz/whatispaint.htm http://nzic.org.nz/ChemProcesses/polymers/1
0D.pdf Product variants: http://en.wikipedia.org/wiki/Paint
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Paint is used as decorative and protective films against a substrate. It is classified into four different groups. Discuss all of the FOUR (4) groups as follows: Water-borne paint Solvent-borne paint Acrylic base paint Alkyd based paint
(15marks) A coating that prematurely reaches the end of its useful life is said to have failed. Even protective coatings properly selected and applied on well-prepared surfaces gradually deteriorate and eventually fail. Describe the following failures of paint. Chalking. Cracking. Dilution. Blistering. Erosion.
(10 marks)
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Paint is used as decorative and protective films against a substrate and made up of seven components. Name and discuss FIVE (5) of these components.
(15 marks) A coating is a covering that is applied to the surface of an object, usually referred to as the substrate. The purpose of applying the coating may be decorative, functional, or both. Differentiate the following types of coating: Primer Undercoat
(10 marks)
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