thermoplastics (rus. термопласты) — polymers which, when heated, reversibly transits into highly-elastic or plastic state.

Description

Thermoplastics are such bulk and widely used polymers as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyformaldehyde, polyacrylates and polymethacrylates, as well as polycarbonate, polyamides, etc. Shaping of a thermoplastic product is achieved through plastic or highly elastic deformation in the polymer. Such processes are slow due to the high viscosity of polymers. Depending on the physical state the polymer is in during the moulding process, varying degree of non-equilibrium is achieved in the finished product due to incomplete relaxation of internal stresses. This imposes certain restrictions on the operation temperature range of the products fabricated using different techniques. If the percentage of highly elastic deformation component goes up, the upper limit of the operation temperature goes down, sometimes to the glass transition point, which is typical of glassy polymer processing.

Thermoplastic products can be fabricated using various techniques. The choice of the method is controlled by many factors, the most important of which are the product’s design features, the polymer’s properties and technological capabilities, conditions of the product’s use and related operational requirements and economic factors.

There is a well-known classification of thermoplastic methods, based on the physical state of the material in-mould:

-plastic polymer moulding, such as injection moulding, extrusion, pressing, sintering, etc.;

-highly elastic polymer moulding; normally, this is done using sheet or film blanks – vacuum moulding, blow moulding, hot forming, etc.;

-solid polymer moulding, based on the ability of these polymers to show forced high-elastic properties – stamping, rolling at room temperature, etc.;

-moulding using polymer solutions and dispersions, typically, by pouring.

Thermoplastic products can also be subject to machining, welding, gluing, foaming and other special processing techniques.

Authors

  • Khokhlov Alexey R.
  • Govorun Elena N.
  • Nazarov Victor G.

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