Paint stripper
Encyclopedia
Paint stripper, or paint remover, is the generic name given to solvent
mixtures designed to remove paint
and other finishes and also to clean the underlying surface. The principal active ingredient is usually dichloromethane
. Formulations with orange oil
(or other terpene
solvents), N-methylpyrrolidone, ester
s such as dibasic ester
s (often dimethyl esters of shorter dicarboxylic acid
s, sometimes aminated, for example, adipic acid
or glutamic acid
), aromatic hydrocarbon
s, dimethylformamide
, and other solvents are known as well. The formula differs according to the type of paint and the character of the underlying surface. Nitromethane
is another commonly used solvent. Dimethyl sulfoxide
is a less toxic alternative solvent used in some formulations.
Paint strippers come in a liquid, or a gel
("thixotropic") form that clings even to vertical surfaces.
The principle of paint strippers is penetration of the paint film by the molecules of the active ingredient, causing its swelling
; this volume increase causes internal strains, which, together with the weakening of the layer's adhesion
to the underlying surface, leads to separation of the layer of the paint from the substrate.
is suitable for shellac
, methyl ethyl ketone is used for cellulose nitrate, and phenol
and cresol
s are employed in some industrial formulas. Benzyl alcohol
is used as well.
Activator
s increase the penetration rate; for dichloromethane water is suitable, other choices are amine
s, strong acids or strong alkalines. The activator’s role is to disrupt the molecular and intermolecular bonds in the paint film and assist with weakening it. Its composition depends on the character of the paint to be removed. Mineral acid
s are used for epoxy
resins to hydrolyze
their ether
bonds. Alkaline activators are usually based on sodium hydroxide. Some cosolvents double as activators. Amine
activators, alkalines weaker than inorganic hydroxides, are favored when the substrate could be corroded by strong acids or bases.
Surfactant
s assist with wetting
the surface, increasing the area of where the solvent can penetrate the paint layer. Anionic surfactants (e.g., dodecyl benzene sulfonate or sodium xylene sulfonate) are used for acidic formulas, cationic or nonionic are suitable for alkaline formulas.
Paint strippers containing surfactants are excellent brush cleaners.
Thickeners are used for thixotropic formulas to help the mixture form gel
that adheres to vertical surfaces and to reduce the evaporation of the solvents, thus prolonging the time the solvent can penetrate the paint. Cellulose
-based agents, e.g., hydroxypropyl cellulose
, are commonly used for mixtures that are not extremely acidic or basic; under such conditions cellulose undergoes hydrolysis and loses effectivity, so fumed silica is used for these instead. Another possibility is using wax
es (usually paraffin wax or polyethylene
or polypropylene
derivates), or polyacrylate gels.
Corrosion inhibitor
s are added to the formula to protect the underlying substrate and the paint stripper storage vessel (usually a tin can) from corrosion
. Dichloromethane decomposes with time to hydrochloric acid
, which readily reacts with propylene oxide
or butylene oxide and therefore is removed from the solution. Chromate
-based inhibitors give the mixture a characteristic yellow color. Other possibilities include polyphosphate
s, silicate
s, borate
s and various antioxidant
s.
Sequestrant
s and chelating agents are used to ‘disarm’ metal ions present in the solution, which could otherwise reduce the efficiency of other components, and assist with cleaning stains, which often contain metal compounds. The most common sequestrants used in paint strippers are EDTA
, tributyl phosphate
, and sodium phosphate.
Colourant
s are added in order to make the substance look different from the competitors’, and to make it easier to see which areas the remover has been applied to.
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
mixtures designed to remove paint
Paint
Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...
and other finishes and also to clean the underlying surface. The principal active ingredient is usually dichloromethane
Dichloromethane
Dichloromethane is an organic compound with the formula CH2Cl2. This colorless, volatile liquid with a moderately sweet aroma is widely used as a solvent. Although it is not miscible with water, it is miscible with many organic solvents...
. Formulations with orange oil
Limonene
Limonene is a colourless liquid hydrocarbon classified as a cyclic terpene. The more common D isomer possesses a strong smell of oranges. It is used in chemical synthesis as a precursor to carvone and as a renewably-based solvent in cleaning products....
(or other terpene
Terpene
Terpenes are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium. They are often strong smelling and thus may have had a protective...
solvents), N-methylpyrrolidone, ester
Ester
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...
s such as dibasic ester
Dibasic ester
In chemistry, a dibasic ester or DBE is an ester of a dicarboxylic acid. Depending on the application, the alcohol may be methanol or higher molecular weight monoalcohols....
s (often dimethyl esters of shorter dicarboxylic acid
Dicarboxylic acid
Dicarboxylic acids are organic compounds that contain two carboxylic acid functional groups. In molecular formulae for dicarboxylic acids, these groups are often written as HOOC-R-COOH, where R may be an alkyl, alkenyl, alkynyl, or aryl group...
s, sometimes aminated, for example, adipic acid
Adipic acid
Adipic acid is the organic compound with the formula 42. From the industrial perspective, it is the most important dicarboxylic acid: About 2.5 billion kilograms of this white crystalline powder are produced annually, mainly as a precursor for the production of nylon...
or glutamic acid
Glutamic acid
Glutamic acid is one of the 20 proteinogenic amino acids, and its codons are GAA and GAG. It is a non-essential amino acid. The carboxylate anions and salts of glutamic acid are known as glutamates...
), aromatic hydrocarbon
Aromatic hydrocarbon
An aromatic hydrocarbon or arene is a hydrocarbon with alternating double and single bonds between carbon atoms. The term 'aromatic' was assigned before the physical mechanism determining aromaticity was discovered, and was derived from the fact that many of the compounds have a sweet scent...
s, dimethylformamide
Dimethylformamide
Dimethylformamide is an organic compound with the formula 2NCH. Commonly abbreviated as DMF , this colourless liquid is miscible with water and the majority of organic liquids. DMF is a common solvent for chemical reactions...
, and other solvents are known as well. The formula differs according to the type of paint and the character of the underlying surface. Nitromethane
Nitromethane
Nitromethane is an organic compound with the chemical formula . It is the simplest organic nitro compound. It is a slightly viscous, highly polar liquid commonly used as a solvent in a variety of industrial applications such as in extractions, as a reaction medium, and as a cleaning solvent...
is another commonly used solvent. Dimethyl sulfoxide
Dimethyl sulfoxide
Dimethyl sulfoxide is an organosulfur compound with the formula 2SO. This colorless liquid is an important polar aprotic solvent that dissolves both polar and nonpolar compounds and is miscible in a wide range of organic solvents as well as water...
is a less toxic alternative solvent used in some formulations.
Paint strippers come in a liquid, or a gel
Gel
A gel is a solid, jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state...
("thixotropic") form that clings even to vertical surfaces.
The principle of paint strippers is penetration of the paint film by the molecules of the active ingredient, causing its swelling
Swelling (medical)
In medical parlance, swelling is the transient enlargement or protuberance in the body and may include tumors. According to cause, it may be congenital, traumatic, inflammatory, neoplastic or miscellaneous....
; this volume increase causes internal strains, which, together with the weakening of the layer's adhesion
Adhesion
Adhesion is any attraction process between dissimilar molecular species that can potentially bring them in close contact. By contrast, cohesion takes place between similar molecules....
to the underlying surface, leads to separation of the layer of the paint from the substrate.
Other components
Various co-solvents are added to the primary active ingredient. These assist with penetration into the paint and its removal and differ according to the target paint. EthanolEthanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
is suitable for shellac
Shellac
Shellac is a resin secreted by the female lac bug, on trees in the forests of India and Thailand. It is processed and sold as dry flakes , which are dissolved in ethyl alcohol to make liquid shellac, which is used as a brush-on colorant, food glaze and wood finish...
, methyl ethyl ketone is used for cellulose nitrate, and phenol
Phenol
Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...
and cresol
Cresol
Cresols are organic compounds which are methylphenols. They are a widely occurring natural and manufactured group of aromatic organic compounds which are categorized as phenols . Depending on the temperature, cresols can be solid or liquid because they have melting points not far from room...
s are employed in some industrial formulas. Benzyl alcohol
Benzyl alcohol
Benzyl alcohol is an organic compound with the formula C6H5CH2OH. The benzyl group is often abbreviated "Bn", thus benzyl alcohol is denoted as BnOH. Benzyl alcohol is a colorless liquid with a mild pleasant aromatic odor. It is a useful solvent due to its polarity, low toxicity, and low vapor...
is used as well.
Activator
Activator
Activator may mean:* Activator , a DNA-binding protein that regulates one or more genes by increasing the rate of transcription* Activator , a type of effector that increases the rate of enzyme mediated reactions...
s increase the penetration rate; for dichloromethane water is suitable, other choices are amine
Amine
Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...
s, strong acids or strong alkalines. The activator’s role is to disrupt the molecular and intermolecular bonds in the paint film and assist with weakening it. Its composition depends on the character of the paint to be removed. Mineral acid
Mineral acid
A mineral acid is an acid derived from one or more inorganic compounds. A mineral acid is not organic and all mineral acids release hydrogen ions when dissolved in water.-Characteristics:...
s are used for epoxy
Epoxy
Epoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....
resins to hydrolyze
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
their ether
Ether
Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...
bonds. Alkaline activators are usually based on sodium hydroxide. Some cosolvents double as activators. Amine
Amine
Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...
activators, alkalines weaker than inorganic hydroxides, are favored when the substrate could be corroded by strong acids or bases.
Surfactant
Surfactant
Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...
s assist with wetting
Wetting
Wetting is the ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. The degree of wetting is determined by a force balance between adhesive and cohesive forces.Wetting is important in the bonding or adherence of...
the surface, increasing the area of where the solvent can penetrate the paint layer. Anionic surfactants (e.g., dodecyl benzene sulfonate or sodium xylene sulfonate) are used for acidic formulas, cationic or nonionic are suitable for alkaline formulas.
Paint strippers containing surfactants are excellent brush cleaners.
Thickeners are used for thixotropic formulas to help the mixture form gel
Gel
A gel is a solid, jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state...
that adheres to vertical surfaces and to reduce the evaporation of the solvents, thus prolonging the time the solvent can penetrate the paint. Cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....
-based agents, e.g., hydroxypropyl cellulose
Hydroxypropyl cellulose
Hydroxypropyl cellulose is a derivative of cellulose with both water solubility and organic solubility. It is used as a topical ophthalmic protectant and lubricant.-Chemistry:...
, are commonly used for mixtures that are not extremely acidic or basic; under such conditions cellulose undergoes hydrolysis and loses effectivity, so fumed silica is used for these instead. Another possibility is using wax
Wax
thumb|right|[[Cetyl palmitate]], a typical wax ester.Wax refers to a class of chemical compounds that are plastic near ambient temperatures. Characteristically, they melt above 45 °C to give a low viscosity liquid. Waxes are insoluble in water but soluble in organic, nonpolar solvents...
es (usually paraffin wax or polyethylene
Polyethylene
Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...
or polypropylene
Polypropylene
Polypropylene , also known as polypropene, is a thermoplastic polymer used in a wide variety of applications including packaging, textiles , stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer banknotes...
derivates), or polyacrylate gels.
Corrosion inhibitor
Corrosion inhibitor
A corrosion inhibitor is a chemical compound that, when added to a liquid or gas, decreases the corrosion rate of a material, typically a metal or an alloy. The effectiveness of a corrosion inhibitor depends on fluid composition, quantity of water, and flow regime...
s are added to the formula to protect the underlying substrate and the paint stripper storage vessel (usually a tin can) from corrosion
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
. Dichloromethane decomposes with time to hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
, which readily reacts with propylene oxide
Propylene oxide
Propylene oxide is an organic compound with the molecular formula CH3CHCH2O. This colourless volatile liquid is produced on a large scale industrially, its major application being its use for the production of polyether polyols for use in making polyurethane plastics...
or butylene oxide and therefore is removed from the solution. Chromate
Chromate
Chromate salts contain the chromate anion, CrO42−. Dichromate salts contain the dichromate anion, Cr2O72−. They are oxyanions of chromium in the oxidation state +6. They are moderately strong oxidizing agents.- Chemical properties :...
-based inhibitors give the mixture a characteristic yellow color. Other possibilities include polyphosphate
Polyphosphate
Triphosphates are salts or esters of polymeric oxyanions formed from tetrahedral PO4 structural units linked together by sharing oxygen atoms. When two corners are shared the polyphosphate may have a linear chain structure or a cyclic ring structure. In biology the polyphosphate esters AMP, ADP...
s, silicate
Silicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
s, borate
Borate
Borates are chemical compounds which contain oxoanions of boron in oxidation state +3. The simplest borate ion, BO33−, has a trigonal planar structure. Other borates are made up of trigonal BO3 or tetrahedral BO4 structural units, sharing oxygen atoms...
s and various antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...
s.
Sequestrant
Sequestrant
A sequestrant is a food additive whose role is to improve the quality and stability of the food products. Sequestrants form chelate complexes with polyvalent metal ions, especially copper, iron and nickel, which serve as catalysts in the oxidation of the fats in the food...
s and chelating agents are used to ‘disarm’ metal ions present in the solution, which could otherwise reduce the efficiency of other components, and assist with cleaning stains, which often contain metal compounds. The most common sequestrants used in paint strippers are EDTA
EDTA
Ethylenediaminetetraacetic acid, widely abbreviated as EDTA , is a polyamino carboxylic acid and a colourless, water-soluble solid. Its conjugate base is named ethylenediaminetetraacetate. It is widely used to dissolve limescale. Its usefulness arises because of its role as a hexadentate ligand...
, tributyl phosphate
Tributyl phosphate
Tributyl phosphate, known commonly as TBP, is an organophosphorus compound with the formula 3PO. This colourless, odorless liquid finds some applications as an extractant and a plasticizer. It is an ester of orthophosphoric acid with n-butanol.- Production :Tributyl phosphate is manufactured by...
, and sodium phosphate.
Colourant
Colourant
A colourant or colorant is something added to something else to cause a change in colour. Colourants can be:* Dyes* Pigments* Biological pigments* Inks* Paint* Coloured chemicals...
s are added in order to make the substance look different from the competitors’, and to make it easier to see which areas the remover has been applied to.
External links
- DIYinfo.org's Paint Removal Wiki - Heaps of practical information on how to remove / strip paint around the house
- JAIC 1993: The composition of proprietary paint strippers
- Patent 6923873 - Paint stripping composition and method of using the same
- http://www.easystrip.co.nz/more_info.php - has pictorial sequence and information on how to strip paint effectively