Chlorinated Rubber Coatings
Chlorinated rubber (CR) is manufactured from natural or synthetic rubber such as polypropylene, polyethylene, or polyisoprene which is degraded to low molecular mass compounds by mastication or addition of radical formers and dissolved in carbon tetrachloride. Chlorine gas is than introduced into the solution and will reacts with the raw material to form CR. The solution is then introduced into boiling water. The CR is than precipitated and vaporized. It is separated from water, rinsed, dried, and ground to form a white powder.
CR has some properties :
- high resistance to oxidizing agents (such as ozone or peroxide), water, inorganic salts, acids, alkalis, and gases.
- good solubility in almost conventional ssolvents except water, aliphatic hydrocarbons, and alcohols.
- good compability with a wide range of paint resins and plasticizers.
- low flammability.
- fungistatic and bacteriostatic behavior.
- compatible with almost all inorganic pigments and extenders, as well as many organic pigments.
Chlorinated rubber has high water resistance, it is used for underwater coatings on steel and concrete.
Apr 17, 2010
Apr 5, 2010
Oil-Based Coatings
Oil-Based Coatings
Oil-based paints (oil paints) are the oldest organic coating materials. The content of Oil paints is natural drying oils such as linseed oil, tung oil, and soybean oil which will undergo autoxidative polymerization in the presence of catalytic driers and atmospheric oxygen. The catalytic driers are metallic soaps such as cobalt, lead, and manganese naphthenates or octoates.
Oil-based paints are tough but not excessively hard. It has limited weather resistance. It will lose its gloss and tend to yellow much more than otehr binders (ca. two years).
The use of oil paint has decrease and have been replaced by other types of binder. Its renewable natural oil are environment friendly as long as toxic pigment and solvent are not used.
Oil-based paints (oil paints) are the oldest organic coating materials. The content of Oil paints is natural drying oils such as linseed oil, tung oil, and soybean oil which will undergo autoxidative polymerization in the presence of catalytic driers and atmospheric oxygen. The catalytic driers are metallic soaps such as cobalt, lead, and manganese naphthenates or octoates.
During curing of paint, the atmospheric oxygen reacts with the oil to form hydroperoxides which will decompose into radicals and then initiate polymerization of the binder. The drier will catalyze the formation and decomposition of the hydroperoxides and thereby accelerate film formation.
Oil-based paints are tough but not excessively hard. It has limited weather resistance. It will lose its gloss and tend to yellow much more than otehr binders (ca. two years).
The use of oil paint has decrease and have been replaced by other types of binder. Its renewable natural oil are environment friendly as long as toxic pigment and solvent are not used.
Apr 1, 2010
Nitrocellulose Lacquers
Nitrocellulose Lacquers
Nitrocellulose (cellulose nitrate) lacquers are a mixture of binders (nitrocellulose and resins), plasticizers, and pigments dissolved or dispersed in organic solvents.
The components of nitrocellulose lacquers are :
a. Nitrocellulose
Nitrocellulose is an outstanding film-forming substance which displays rapid solvent evaporation (short drying time). Nitrocellulose is characterized by its nitrogen content and solubility. The nitrogen contents are :
- Ester-soluble nitrocellulose 11.8 - 12.2 wt%
- Alcohol-soluble nitrocellulose 10.9 - 11.3 wt%
Based on its viscosity nitrocellulose classified into three category : high-viscosity, medium-viscosity, and low-viscosity.
High-viscosity nitrocellulose have good flexibility combined with a high crack resistance. It is used where high mechanical stress is to be expected (e.g., in leather coatings, putty, adhesives). Only lacquers with low solids contents can be obtained from high-viscosity nitrocellulose.
Medium-viscosity nitrocelluloses have the broadest application range, such as furniture lacquers, paper and metal coatings.
Low-viscosity nitrocellulose is used to prepare high-solids lacquers. The low-viscosity nitrocellulose produces hard to brittle coating films, plasticizers and plastifying resins must be added to the lacquer formulation. They are used in putty, dipping paints, and printing inks.
b. Resins
Many synthetic resins such as alkyd, ketone, urea, maleate, and acrylic can be combined with nitrocellulose to make nitrocellulose lacquers. Selection of the resins based on price, color, influence on solvent release, gloss, hardness, sandability, yellowing, and durability of the final coating.
c. Plasticizers.
Plasticizers are used in coatings for the following purposes:
- To improve adhesive strength and gloss
- To improve mechanical properties such as elongation, pliability, buckling strength, crease resistance, and deep-drawing ability
- To increase resistance to light, heat, cold, and sudden temperature changes (cold-check test)
Plasticizers may be solvents such as dibutyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, tricresyl phosphate, and triphenyl phosphate. Or nonsolvent such as crude and blown vegetable oils, stearates, and oleates.
d. Pigment
The use of pigment in nitrocellulose lacquers is same with other type of paint.
e. Solvents
The mixture of solvents has influence specially in drying time. The last solvent that evaporate should be a true solvent (can disslove) all material from the formula. Some solvents that are used are acetate esters (such as : ethyl acetate, butyl acetate, or propyl acetate) and ketones (such as : acetone, methyl ethyl ketone, methyl isobutyl ketone).
Uses
Nitrocellulose lacquers is used in printing inks employed in flexographic, gravure, or silk-screen printing. The most important uses of nitrocellulose lacquers are for coating wood, metal (automotive repair), paper, foil (cellophane, aluminum), leather, textiles, and in nail polish.
Mar 30, 2010
PIGMENTS -Types
PIGMENTS -Types
Pigment ussually divide into some categories : White and colored pigment; metallic pigment; and functional pigment.
White pigments : lithopone and titanium dioxide
Colored pigments : red/yellow - iron oxide, blue/green-phtalocyanine, black-carbon or lamp black.
Metallic pigment : metallic appearance-alluminium flake, pearlescene-titania and surface modified talc
Functional pigments : filler-limestone and clay, UV stabilizer-lithopone and zinc sulfide, conductive ability-nickel/copper/silver powder and barium titanate.
Pigment ussually divide into some categories : White and colored pigment; metallic pigment; and functional pigment.
White pigments : lithopone and titanium dioxide
Colored pigments : red/yellow - iron oxide, blue/green-phtalocyanine, black-carbon or lamp black.
Metallic pigment : metallic appearance-alluminium flake, pearlescene-titania and surface modified talc
Functional pigments : filler-limestone and clay, UV stabilizer-lithopone and zinc sulfide, conductive ability-nickel/copper/silver powder and barium titanate.
Resin - Convertible Binders
Resin - Convertible Binders
1. Oils and Oleoresinous Varnishes
The use of oils in paint formulation has already decline. Their use are limited in certain types of primer for steel and timber (refined linseed oil and linseed stand oil). Oils are often used for preparation of oleoresinous varnishes, specially for oil-modified alkyd resins.
Vegetable oils are classified as drying or nondrying oils.
Drying oils : linseed oil and tung oil will readily dry when exposed to oxygen. Soybean oil is called as semidrying oil, because of not drying quickly. The drying process is oxidative polimerization or auto-oxidation. The oxidation rate is slow but can be accelerated by the addition of driers such as cobalt or lead naphthenates.
Nondrying oils : castor oil and olive oil. The nondrying oil can not be oxidized readily. It can be converted to drying oil by heating (to 280 deg. C) for several hours to break down some of the constituent acids of the oil.
2. Alkyd resins
Alkyd resins are modified with some oils such as soya, linseed, dehydrated castor, and coconut oil.
Alkyds can be made directly from oil (triglyceride), a polyol, or an acid. The percentage of oil that contained in an alkyd will classifies the end use of the alkyd and affects properties such as speed of drying, flexibility, durability, etc.
The resin can be combined with such resins as acrylics, vinyl toluene, silicones, and amino-resins. They are fairly inexpensive and they have a variety of properties. These makes them popular for use in industrial coatings.
3. Polyester resins
Polyester resins are typically used in heat-cured coatings that need to be high in paint solids and low in solvent content. They have extremely good color retention that provides good over-bake protection and very good UV resistance.
4. Acrylic resins
Acrylic resins are very versatile and popular for industrial liquid coatings. It is happen because they provide toughness, good weathering ability, and has good resistance to abrasion and chemical attack.
The resins are the polymers and copolymers of the esters of methacrylic and acrylic acids.
5. Amino resins
They are usually used in baked coatings as cross-linking agents. They are used in proportions up to 50% of the total vehicle binder. They can be used with alkyds, polyesters, epoxies, thermosetting acrylics, phenolics, and other heat reactive resins.
Melamine and urea–formaldehyde are the most common examples of this resin.
6. Epoxy resins
Epoxy resins are have excellent corrosion and chemical resistance. But they tend to fade and chalk when exposed to sunlight (UV). They are used for interior applications or as primer for exterior applications. The epoxy resin is usually cross-linked with melamine or urea resin at high curing temperatures.
7. Urethane resins
Urethane resins are very good in chemical resistance, toughness and abrasion resistance, and exterior durability.
Urethanes are the reaction products of isocyanates with materials that have hydroxyl groups. The isocyanates are can be in many different forms, but the most widely used is Toluene Diisocyanate (TDI). The TDI has a noticeable vapor pressure and has an irritant effect on the mucous membranes and so requires special handling.
1. Oils and Oleoresinous Varnishes
The use of oils in paint formulation has already decline. Their use are limited in certain types of primer for steel and timber (refined linseed oil and linseed stand oil). Oils are often used for preparation of oleoresinous varnishes, specially for oil-modified alkyd resins.
Vegetable oils are classified as drying or nondrying oils.
Drying oils : linseed oil and tung oil will readily dry when exposed to oxygen. Soybean oil is called as semidrying oil, because of not drying quickly. The drying process is oxidative polimerization or auto-oxidation. The oxidation rate is slow but can be accelerated by the addition of driers such as cobalt or lead naphthenates.
Nondrying oils : castor oil and olive oil. The nondrying oil can not be oxidized readily. It can be converted to drying oil by heating (to 280 deg. C) for several hours to break down some of the constituent acids of the oil.
2. Alkyd resins
Alkyd resins are modified with some oils such as soya, linseed, dehydrated castor, and coconut oil.
Alkyds can be made directly from oil (triglyceride), a polyol, or an acid. The percentage of oil that contained in an alkyd will classifies the end use of the alkyd and affects properties such as speed of drying, flexibility, durability, etc.
The resin can be combined with such resins as acrylics, vinyl toluene, silicones, and amino-resins. They are fairly inexpensive and they have a variety of properties. These makes them popular for use in industrial coatings.
3. Polyester resins
Polyester resins are typically used in heat-cured coatings that need to be high in paint solids and low in solvent content. They have extremely good color retention that provides good over-bake protection and very good UV resistance.
4. Acrylic resins
Acrylic resins are very versatile and popular for industrial liquid coatings. It is happen because they provide toughness, good weathering ability, and has good resistance to abrasion and chemical attack.
The resins are the polymers and copolymers of the esters of methacrylic and acrylic acids.
5. Amino resins
They are usually used in baked coatings as cross-linking agents. They are used in proportions up to 50% of the total vehicle binder. They can be used with alkyds, polyesters, epoxies, thermosetting acrylics, phenolics, and other heat reactive resins.
Melamine and urea–formaldehyde are the most common examples of this resin.
6. Epoxy resins
Epoxy resins are have excellent corrosion and chemical resistance. But they tend to fade and chalk when exposed to sunlight (UV). They are used for interior applications or as primer for exterior applications. The epoxy resin is usually cross-linked with melamine or urea resin at high curing temperatures.
7. Urethane resins
Urethane resins are very good in chemical resistance, toughness and abrasion resistance, and exterior durability.
Urethanes are the reaction products of isocyanates with materials that have hydroxyl groups. The isocyanates are can be in many different forms, but the most widely used is Toluene Diisocyanate (TDI). The TDI has a noticeable vapor pressure and has an irritant effect on the mucous membranes and so requires special handling.
Resin - Nonconvertible resins
Resin - Nonconvertible resins
1. Cellulose Ester
Some of the cellulose ester are cellulose acetate, cellulose acetate butyrate (CAB), and cellulose acetate propionate (CAP).
Cellulose acetate is the simplest organic cellulose ester, offers excellent properties in coating films (e.g., flame resistance, high melting point, toughness, and clarity).
2. Nitrocellulose
Nitrocellulose is an outstanding film-forming substance which displays rapid solvent evaporation (short drying time). Nitrocellulose is the common name for the nitration product of cellulose. It is derived from cellulose, a material from plants, and therefore a renewable source. The commercial product is made by reacting cellulose with nitric acid.
Soluble nitrocellulose has a unique combination of properties such as toughness, durability, solubility, gloss, and rapid solvent release. The most important areas of use of nitrocellulose lacquers are for coating wood, metal (e.g., automotive repair), paper, foil (cellophane, aluminum), leather,and textiles and in nail polish.
3. Chlorinated Rubber
Chlorinated rubber (CR) is manufactured by using natural or synthetic rubber such as polyethylene, polypropylene or polyisoprene which is degraded to low molecular mass compounds by mastication or addition of radical formers and dissolved in carbon tetrachloride (CTC). Chlorine contents are typically 64-68 wt %. Chlorine gas is introduced into this solution and reacts with the raw material to form CR. The solution is then introduced into boiling water. The CR is precipitated, and the solvent vaporizes. The CR is separated from water, rinsed, dried and ground to form a white powder which is the saleable product.
The main area of use of chlorinated rubber paints is for underwater coatings on ships. Favorable properties for this application are high water resistance, rapid drying, good mutual adhesion of the individual layers, and the fact that old coats of paint can easily be renewed.
4. Vinyl resins
Vinyl resins are synthesized by polymerization of monomers that contain CH2=CH groups.
Paints and coating materials based on vinyl resins are generally physically drying.
Vinyl resins are include polyolefins, poly(viny1 halides) and vinyl halide copolymers, poly(viny1 esters), poly(viny1 alcohol), poly(viny1 acetals), poly(viny1 ethers), and polystyrene.
1. Cellulose Ester
Some of the cellulose ester are cellulose acetate, cellulose acetate butyrate (CAB), and cellulose acetate propionate (CAP).
Cellulose acetate is the simplest organic cellulose ester, offers excellent properties in coating films (e.g., flame resistance, high melting point, toughness, and clarity).
2. Nitrocellulose
Nitrocellulose is an outstanding film-forming substance which displays rapid solvent evaporation (short drying time). Nitrocellulose is the common name for the nitration product of cellulose. It is derived from cellulose, a material from plants, and therefore a renewable source. The commercial product is made by reacting cellulose with nitric acid.
Soluble nitrocellulose has a unique combination of properties such as toughness, durability, solubility, gloss, and rapid solvent release. The most important areas of use of nitrocellulose lacquers are for coating wood, metal (e.g., automotive repair), paper, foil (cellophane, aluminum), leather,and textiles and in nail polish.
3. Chlorinated Rubber
Chlorinated rubber (CR) is manufactured by using natural or synthetic rubber such as polyethylene, polypropylene or polyisoprene which is degraded to low molecular mass compounds by mastication or addition of radical formers and dissolved in carbon tetrachloride (CTC). Chlorine contents are typically 64-68 wt %. Chlorine gas is introduced into this solution and reacts with the raw material to form CR. The solution is then introduced into boiling water. The CR is precipitated, and the solvent vaporizes. The CR is separated from water, rinsed, dried and ground to form a white powder which is the saleable product.
The main area of use of chlorinated rubber paints is for underwater coatings on ships. Favorable properties for this application are high water resistance, rapid drying, good mutual adhesion of the individual layers, and the fact that old coats of paint can easily be renewed.
4. Vinyl resins
Vinyl resins are synthesized by polymerization of monomers that contain CH2=CH groups.
Paints and coating materials based on vinyl resins are generally physically drying.
Vinyl resins are include polyolefins, poly(viny1 halides) and vinyl halide copolymers, poly(viny1 esters), poly(viny1 alcohol), poly(viny1 acetals), poly(viny1 ethers), and polystyrene.
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