A binder or binding agent is any material or substance that holds or draws other materials together to form a cohesive whole mechanically, chemically, by adhesion or cohesion.
Astringents are substances that can harden as a result of physical and chemical processes. Passing from the dough to the stone-like state, the binding material binds stones or aggregate grains to each other. This property of binders is used for the manufacture of mortars – masonry, plastering and special, as well as concretes, silicate bricks, asbestos cement and other raw materials.
Astringents on structure are divided on organic and inorganic (mineral). To organic include bitumen, tar, animal glue, polymers. They go into working order by heating, melting, or dissolving in organic liquids. Inorganic include lime, cement, construction gypsum, magnesia cement, liquid glass, etc. They are usually closed by water, less often by aqueous solutions of salts. In turn, they are divided into air, hydraulic, acidic astringents and astringent autoclaved hardening.
In a more narrow sense, binders are liquid or dough-like substances that harden by a chemical or physical process and bind fibres, filler powder and other particles added into it. Examples include glue, adhesive and thickening.
Examples of mechanical binders are bond stones in masonry and tie beams in timber framing.
Classification
Binders are loosely classified as organic (bitums, animal and plant glues, polymers) and inorganic (lime, cement, gypsum, liquid glass, etc.).
Based on their chemical resistance, binders are classified by the field of use: non-hydraulic (gypsum, air-cements, magnesia, hydrated lime), hydraulic (Roman cement, portland cement, hydraulic lime), acid-resistant (silicon fluoride cement, quartz cement), and autoclavable (harden at 170 to 300°С i.e. 8-16 atm pressure and, e.g., comprise CaSiO3 materials) .
Physical properties
Some materials labeled as binders such as cement have a high compressive strength but low tensile strength and need to be reinforced with fibrous material or rebar if tension and shear forces will be applied.
Other binding agents such as resins may be tough and possibly elastic but can neither bear compressive nor tensile force. Tensile strength is greatly improved in composite materials consisting of resin as the matrix and fiber as a reinforcement. Compressive strength can be improved by adding filling material.
Physically
In emulsions and dispersions, the binder is suspended in a solvent or diluent. The physical solidification occurs by evaporation or drying of the solvent. The active components of the binder approach each other and develop even stronger mutual cohesion. Examples of physically solidifying binders are polymer and acrylic resins.
Some physically-solidified binders can be redissolved by the re-addition of solvent, e.g. Nitrocellulose (cellulose nitrate), chlorinated rubber and glue or paste.
Chemical
This type of binding is a chemical reaction of the components, i. H. usually based on the formation of polymer chains, which is also called crosslinking, resinification or polymerization.
If a solvent is included, the weak binding of the molecules of the solvent to the molecules of the binder initially impedes crosslinking of the binder. Only when the solvent has volatilized, the binder solidifies.In some cases, the binder solidifies without significant reduction in volume or weight, e.g. B. in two-component resins.
The chemical hardening can be done in different ways:
by oxidation, ie absorption of atmospheric oxygen and subsequent polymerization (eg, for drying oils, natural resin and some synthetic resins such as alkyd resin and epoxy esters)
by polymerization (such as in the case of polyester)
By polycondensation (such as in condensation resins such as phenolic resin, urea resin and melamine resin), in this case, water or other substance is released in the crosslinking and evaporated
by polyaddition (such as in reaction resins such as polyurethane and epoxy resin)
by chain polymerization
In some materials, the crosslinking comes only by adding a hardener (eg epoxy and polyester resin), a crosslinking agent (sulfur, peroxides or metal oxides in the vulcanization of rubber), a catalyst (eg acid or siccatives) or by supply of Heat or UV radiation.
The chemical drying is irreversible.
Features
In the process of stiffening a binder, two phases are distinguished. During the first phase, called an outlet, one passes from the initial fluidity to a more substantial mass capable of maintaining the imparted form. The setting is followed by hardening, in which there is a continuous increase in mechanical resistance.
The socket has a duration that, depending on the case, can go from a few minutes to a few tens of hours, while the hardening extends over an indefinite period of time.
Uses
In art, binders have use in painting, where they hold together pigments and sometimes filling material to form paints, pastels, and other materials. Binders used include wax, linseed oil, gum arabic, gum tragacanth, methyl cellulose, gums, or protein such as egg white or casein. Glue is traditionally made by the boiling of hoofs, bones, or skin of animals and then mixing the hard gelatinous residue with water. Natural gum-based binders are made from substances extracted from plants.
Larger amounts of dry substance are added to liquid binders in order to cast or model sculptures and reliefs.
In cooking, various edible thickening agents are used as binders. Some of them, e.g. tapioca flour, lactose, sucrose, microcrystalline cellulose, poly vinyl pyrrolidone and various starches are also used in pharmacology in making tablets.
Tablet binders include lactose powder, sucrose powder, tapioca starch (cassava flour) and microcrystalline cellulose.
In building construction, concrete uses cement as a binder. Asphalt pavement uses bitumen binder.
Traditionally straw and natural fibres are used to strengthen clay in wattle-and-daub construction and in the building material cob which would otherwise become brittle after drying. Sand is added to improve compressive strength, hardness and reduce shrinkage.
The binding property of clay is also used widely to prepare shaped articles (e.g. pots and vases) or to bind solid pieces (e.g. bricks).
In composite materials, epoxy, polyester or phenolic resins are common. In reinforced carbon-carbon, plastic or pitch resin is used as a source of carbon released through pyrolysis. Transite, hypertufa, papercrete and petecrete used cement as a binder.
In explosives, wax or polymers like polyisobutylene or styrene-butadiene rubber are often used as binders for plastic explosives. For polymer-bonded explosives, various synthetic polymers are used.
In rocket fuels, polybutadiene acrylonitrile copolymer was used in 1960-70’s big solid-fuel booster rocket fuels.
Organic binders, designed to disintegrate by heat during baking, are used in sintering.
Types of binders
Depending on their composition, binders can be classified into two main families: mineral binders and organic binders.
mineral binders: depending on how they are hardened, they can be classified into two sub-families:
aerial binders: air hardening due to a carbonation reaction: aerated lime, clays;
hydraulic binders: curing in a humid environment or in water due to a hydration reaction of silicates or aluminates: hydraulic lime, cement (prompt cement, Portland cement, aluminous cement), plaster, slag.
organic binders:
hydrocarbon binders: bitumens, tars;
resins and especially polymers: aminoplasts, for example, are polymers widely used in the wood industry and its derivatives.
Mineral binders
Inorganic (mineral) binders are called powdered finely divided substances, which when mixed with water (sometimes with salt solutions) form a plastic dough, which subsequently solidifies and unites loose solids in the monolith.
All mineral binders are obtained by the following technology: 1. Extraction of raw materials; 2. Preparation of raw materials (magnetic separation, crushing, washing); 3. Roasting of raw materials, which is carried out at different temperatures; 4. Grinding of the binder obtained;
All mineral binders are divided into 4 groups:
1. Air astringents. These are astringents that, after mixing with water, harden and last for a long time retain their properties only in the air. This is due to the fact that the resulting new hydrate compounds are readily soluble in water. Air binders should only be used in air dry conditions. Examples: gypsum, air lime, magnesian binders, etc.
2. Hydraulic binders. These are astringents that harden and last for a long time retain their properties in water. They can be used for a long time in the aquatic environment, because they form hydrate compounds that are resistant to the aquatic environment. Examples: romantsement, portland cement, etc.
3. Acid-resistant astringents. These are astringents that can be used for a long time when exposed to acids. Example: acid-resistant, silicofluorinated, quartz cements, etc.
4. Autoclave binders. These are astringent substances that harden only when processed in autoclaves, i. E. at a temperature of 170-300 ° C and a pressure of 8 to 16 atmospheres. Example: all binders obtained on the basis of lime and any siliceous or aluminous component.
Organic binders
Organic binders are mixtures of high molecular weight hydrocarbons. They are a viscous or liquid material that goes into operation when the temperature changes or when contact with organic liquids (in some cases, ultraviolet radiation is used).
The main organic binders are:
1. Bitumen is a mixture of hydrocarbons and their chemical derivatives containing: oxygen, sulfur, nitrogen and some metal compounds. It is mainly used as raw material for asphalt.
2. Degty – viscous liquids of black or brown color, consisting of hydrocarbons and their sulfurous, nitrogenous and oxygen derivatives. They are used in road construction and for the production of waterproofing materials.
Food binding agent
A food binding agent is used in dishes to give liquid food products (such as soups, gravies, sauces, and custards) the desired thickness without changing the properties of the dish too much, such as the taste.
There are starchy binders (eg flour, potato flour and corn) and non-starchy binders (eggs, gelatin, butter).
Starch-containing binders are often odorless, colorless and odorless and have the property to swell and bind liquid as soon as it is heated. A commonly used binder is corn starch, also known under the trade name Maïzena.
Flour is often used to make gravies and sauces thicker. Corn starch is often used in soups. Yoghurt is mainly used in Eastern Europe and the Middle East as a binder. Egg yolks are rich in flavor and give a soft mouthfeel to a dish and by heating it in a custard for example, it thickens.
Binder must be used carefully in dishes. Some binders lose power as soon as it is boiled too long or too hot. Binder should be carefully added to the dish during preparation. If too much binder is used, adding water can provide a solution, but this results in loss of taste and texture. Also, the use of some binders can be harmful to people suffering from celiac disease or gluten intolerance.
In painting
A paint consists of two ingredients: the pigment or dye and the binder.
The binder performs three functions:
give cohesion to the pigments so that the pictorial material can be manipulated with a brush or a knife. The binder coats the pigment powder and the agglutin to form a more or less liquid or thick paste;
allow the colored material to dry and harden to form a strong and durable pictorial film. This solidification (or siccativation in the case of oil) can be permanent (acrylic, watercolor) or reversible (gouache, wax).
Give a particular and wanted appearance to a type of painting3 (matt, shiny, mirror, etc.)
In the artistic field
Among the various binders available to the painter are:
drying oil (linseed oil, safflower oil, walnut oil, poppy oil) for oil painting;
gum arabic for watercolor and gouache);
alkyd, acrylic or vinyl resins for paints of the same name;
the egg for the tempera;
wax for encaustic painting and wax pastels.
In the industrial field and in building painting
This section is empty, insufficiently detailed or incomplete. Your help is welcome ! How to do ?
Here is a list of ten binders4:
the vinyl binder;
the acrylic binder;
alkyd and glycerophthalic binders;
the siloxane binder;
the epoxy binder;
the polyurethane binder;
urethane alkyd binders;
linseed oil;
beeswax;
lime.
In the inks
Inks in the Far East (see India ink) in the traditional print (print), whether artistic or industrial, as in brush writing are made of soot that is mixed with water, which is enough to bind soot and paper.
The typographic ink invented by Guttenberg uses linseed oil as a binder, it is one of the revolution, with the printing press that will make it famous.