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Additives ( Latin: additivum "added, enclosed") - also called auxiliary substances or additives - are substances that are added to products in small quantities in order to achieve or improve certain properties.

Additives are used to achieve a positive effect on production , storage , processing or product properties during and after the use phase. In contrast to fillers , additives usually only contribute a few percent to the total volume and are very finely distributed in the material (often dissolved).

Use of additives


Additives are usually optimized for the respective application. For example, additives in fuels have to be more hydrophobic , while biocides in water cycles are typically hydrophilic or soluble .

In addition to specific properties, the following requirements are placed on additives:

In addition, there are the general requirements for all raw materials:

The amount used is usually specifically coordinated. In general, the amount is very small and usually comprises less than 1% of the total formulation.

In the case of plasticizers, however, the amount can be up to 30%.

Typical additives

The additives typically have a broad and very heterogeneous group of possible applications.

However, raw materials can also take on the function of an additive which are usually not used as an additive or are not referred to as such.

Additives usually increase the material price of the manufactured product, since additives are specialty chemicals that are only produced in small quantities. Depending on the type and mode of action of the additive, they can also be hazardous to health. In more complex formulations , interactions between different additives used at the same time and a resulting reduced or even eliminated effect cannot be ruled out.

Special applications

For fuels

In the case of fuels , additives are added in order to strengthen or improve various properties, such as: B. with gasoline to increase the knock resistance (previously tetraethyl lead ; due to its effect as a catalyst poison , lead-free anti- knock agents are used today ), to improve combustion, to clean / keep the fuel system including valves and combustion chamber clean, to improve shelf life. In the case of diesel there are additives for improving the low-temperature properties (see Winter Diesel , Cloud Point , Cold Filter Plugging Point ). These additives are added by the mineral oil companies to their own fuels such as those produced in a refinery (so-called branded fuel ). Free filling stations , on the other hand, usually only receive the standardized basic fuel without additives, which, however, also meets all standard requirements. The fuels sold at branded petrol stations are often mixed with dyes that give the liquids the respective brand color of the mineral oil company. In addition to optimizing diesel fuels for resistance to cold, there are other uses for additives in diesel. Two other important modes of action that are decisive for certain branches of industry are, on the one hand, the stabilization of the fuel during storage and the increase in efficiency during deflagration in the engine. The storage stability of commercial diesel decreases over time. This effect is also known in Germany as the " diesel pest ". It is caused by the watering down of the fuel, as water promotes the growth of microorganisms, yeast and other fungi, which results in deposits on the bottom of fuel tanks. This silt was called the plague in common parlance. By adding additives, this dilution can be delayed, the formation of silt can be almost completely prevented (often through the addition of biocides ) and the storage stability can thus be partially multiplied.

Another important aspect is the increase in the degree of efficiency between burned (for gasoline engines) / deflated (for diesel engines) fuel and the power converted. Here, some additives increase the octane or cetane number and thus ensure considerably more power and efficiency in the engine.

In the case of gasoline engines operated with natural gas ( CNG ) and autogas ( LPG ), it is advisable to add additives to lubricate and cool the valve seats. Since the additives cannot be filled in via the tank during gas operation, there are special installation sets that draw the liquid additive metered through a valve from a bottle using the intake air directly into the carburetor. There it is atomized drop by drop in the gas / air mixture and thus reaches the valves. Similarly, lead substitutes are sometimes used in classic cars because of a suspected lubricating effect .

In newer diesel engines in the truck sector, the standardized urea solution AUS 32 is not sprayed as an additive during combustion, but from an additional tank usually attached next to the diesel tank into a special nitrogen oxide catalytic converter. This means that pollutant emissions that are hazardous to health and the environment can be greatly reduced and the strict standards of Euro 4 , Euro 5 and Euro 6 can be met.

For lubricants

In principle, all lubricants consist of a base fluid (mostly base oil) and other ingredients, which are called additives. Additives for lubricants are used in lubricating oils, cooling lubricants and lubricating greases.

The tribological properties of the lubricant are improved with the following additives:

The following additives are required to meet additional requirements for the lubricant:

The additives are mixed with the base oil (up to 30%). Depending on the type of application, the additives are selected to ensure the required properties. In the case of gear oils, additives are used for certain purposes, e.g. B. essential to increase the compressive strength and shear strength. A typical additive in engine oils for internal combustion engines is molybdenum disulfide .

For fuels and lubricants especially for aircraft engines

Usual additives in aircraft fuels and aircraft lubricating oils are (in alphabetical order of the substance classes):

Check for turbidity
Leaded gasoline

AvGas contains in addition to other additives or valve seat wear- protection agents, anti-knock agents such as tetra-ethyl lead ( "TEL") together with 1,2-di-bromo-ethane or 1,2-di-chloro-ethane and so-called Free radical scavengers ( to form volatile lead bromide or lead chloride as an end reaction product and to prevent lead oxide deposits). There are fuels with different lead contents on the market ( low lead (LL); very low lead (VLL); or unleaded (UL) " almost all avgas on the US market today [2013] is low lead ". Up to 560 mg lead / Liters in Avgas 100LL (octane number 100, "little lead") By 2018, the Piston Aviation Fuel Initiative will test whether lead additives can finally be omitted; worldwide [2015] an estimated 230,000 piston aircraft engines are in use. Other anti-knock agents used are (methylcyclopentadienyl ) manganese tricarbonyl and ferrocene

The worldwide consumption of additives for aviation fuels was 30,000 tons in 1990, for all fuels (including motor vehicle fuels ), detergents had the largest share (50%), followed by flow improvers (13%), cetane number improvers (8%), antioxidants (7%) , Lubricating performance improvers (approx. 5%), anti-icing agents and anti-corrosion agents (3%)

For coating materials

Paint additives are auxiliaries that are added in small amounts to a coating material in order to give it certain properties or to improve it.

In addition to the price-performance ratio, the selection criteria are the effectiveness and the mode of operation .

When using it, one must always pay attention to whether there are any interactions between additives. This is particularly common with substances that are surface-active - surfactants can cause foam, defoamers, on the other hand, craters , wetting disorders and similar effects. The effects of the two groups of additives are opposite to one another and can therefore cancel each other out in the worst case.

Most additives are liquid or in solid form. This makes training very easy. After dispersion, they are added and stirred in. Additives that are supposed to influence the production process, e.g. B. defoamers , wetting and dispersing agents are added before dispersing.

If several additives are used, these are added individually. In addition, thorough mixing should take place after each additive in order to rule out interactions.

For plastics

Additives are used in plastics:

  • to prevent degradation (corrosion) due to autoxidation,
  • as alkyl radical scavengers in production (thermal decomposition of thermoplastics during melting),
  • as stabilizers :
  • Compatibilizers or compatibilizers: Thermoplastic polymers are immiscible with one another in the molten state. Compatibilizers lower the interfacial tension between the phases in copolymers and reduce the phase separation and agglomeration of the different basic material molecules.
    • Impact modifier : Toughness describes the resistance of a material to breakage or crack propagation , as can occur in the event of plastic deformation . The impact resistance describes the temperature-dependent behavior of a material when exposed to energy ( impact energy or impact energy ) a portion of the kinetic energy to be absorbed by deformation. If the impact strength is low, the sample would break brittle or crumble. The properties of plastics can change significantly depending on how they are processed; for injection molding , the literature gives examples of what can have an influence on mechanical properties: heating rate of the granulate with local overheating, temperature, mixing, dwell time in the melted state, the injection pressure and the holding pressure time , the temperature of the mold and the cooling time " . Impact modifiers improve the ductility during processing and use of the articles made from them.
  • Processing aids,
  • Antistatic agents,
  • Dyes,
  • Optical brighteners,
  • Propellant,
  • Flame retardants,
  • Fillers and reinforcing agents,
  • Adhesion promoter
  • and biocides.

For medicines

As excipient or excipient, an additive in drugs is called, which improves the taste, odor or appearance, but has no pharmacological effect.

For food

Food additives are used to improve the structure (e.g. flowability or bite), taste, smell, appearance ( e.g. through coloring or glossing agents), chemical shelf life (e.g. using emulsifiers or stabilizers) and microbiological shelf life (e.g. through preservatives ) of processed foods, i.e. yours To improve the utility and nutritional value , as well as to ensure the trouble-free production of the food.

For concrete

See concrete admixtures and admixtures .


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  • Kurt Wehlte : Materials and techniques of painting . Otto Maier, Ravensburg 1967, ISBN 3-473-48359-1 .

Web links

Wiktionary: Additive  - explanations of meanings, word origins, synonyms, translations

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