Chemistry

Granules

Granules


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Area of ​​Expertise - Macromolecular chemistry, materials science

A granulate consists of granulate grains (granules), most of which have a similar, but not exactly the same, geometric shape. Granules are often cylindrical or spherical in shape.

Many plastics and fertilizers, for example, are commercially available as granules.

Learning units in which the term is dealt with

Polystyrene30 min.

Chemistrytechnical chemistryProduction engineering

The module gives an insight into the discovery and use of polystyrene. Technical production processes for polystyrene (PS) are presented.

Injection molding30 min.

Chemistrytechnical chemistryProduction engineering

This learning unit introduces the processing technology of injection molding.


Not yet sure which subject is the right one? Would you like to talk directly to students about different study programs? During the study talk on June 24th there is also a zoom room in which three of our buddies are available to answer questions about the courses in physics, physics teaching and energy science.

Everyone has ever gotten a wipe on the door handle. Because if two different substances come into contact, an electrostatic charge can occur, which dissipates with a small flash of lightning. This frictional electricity can be used to separate particles in exhaust gases, but it can also trigger unintentional explosions, e.g. when flammable liquids or powders are filled.


Table of contents

The particles of granular matter have a macroscopic size (in material science they are called grain) and are therefore not noticeably influenced by quantum effects or thermal movement. They only interact via contact forces (friction force). It is not a matter of an aggregate state of matter, but a collection of solids. Granular matter sometimes behaves like a single solid - for example stones can lie on sand without sinking in - and sometimes like a liquid: sand adapts to the shape of a vessel and "flows" out of it when it is tilted. When emptying a silo or bunker, the bulk material sometimes behaves like a solid (does not flow), sometimes like a liquid (flows or shoots out).

The physics of granular matter is based on mechanical and, with sufficiently small grains, electrostatic interactions. Due to the large number of reaction partners, however, a multi-body problem with high complexity arises, which leads to a wide range of effects. One example is the Brazil nut effect, in which moving a mixture of grains of different sizes causes the larger grains to drift to the surface. The properties of granular matter change greatly when small amounts of liquid are added, as this lowers the friction of the particles and, due to cohesion, can lead to mutual attraction. This explains the stability of sand castles, for example.

Granular matter has only been an active research area for a few decades, so that many phenomena are known from everyday life or physical experiments, but are not yet clearly explained theoretically.

Alternatively, the mechanical behavior of granular matter can also be described using the theory of porous media. The grains are not taken into account individually, but are included in the description averaged over their volume fraction.

Knowledge of granular matter can be of great importance for manufacturing processes and warehousing in industry.

Another important application is the physics of geophysical mass movements such as debris flows and avalanches. Rock falls and debris in waterfalls can also be modeled as - huge - particles. These models form the basis for hazard zone labeling and disaster control.

In transportation are the term loose bulk and the underlying mechanical-physical processes of importance for the safety and stability of cargo ships and aircraft. The explosive effect (see also dust explosion) of granular matter, due to its large surface, oxidative effect and static electricity, was only recognized as a risk factor after serious accidents.


Precautions

Pipe cleaners should be handled with care, as, depending on their composition, chemical burns can occur if they come into contact with the skin. Chemical burns with an alkali are often more dangerous than chemical burns with an acid, since the "fat layer" of the skin is saponified by the alkali: the fat is broken down into glycerine and fatty acids. Most pipe cleaners are marked with a corresponding hazard symbol.

Furthermore, with many products, sufficient ventilation must be ensured during use due to the development of gas.



Comments:

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  2. Lamandre

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  3. Jose

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