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Plastic coating is a term that is commonly used in technology but is nevertheless ambiguous. It can be understood to mean the coating of
plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...
(e.g., metallization of plastics) or the coating of other materials (e.g.,
electrical cable An electrical cable is an assembly of one or more wires running side by side or bundled, which is used to carry electric current. One or more electrical cables and their corresponding connectors may be formed into a ''cable assembly'', which ...
) with plastics.


Polymer coating

A polymer coating is a form of plastic coating or surface coating and consists of a
plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...
base. There are also
tribological Tribology is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication and wear. Tribology is highly interdisciplinary, drawing on many academic field ...
polymer coatings that can be adapted to numerous application needs thanks to the variety of
polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
s available. The coating reduces
friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of t ...
and abrasion, thus preventing the product from wearing out due to
corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engin ...
and scratching.


Advantages

Coatings made of polymers can be produced from various compounds. They can therefore be applied to almost any surface.
Polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
coatings are accordingly particularly suitable for places where
plain bearing A plain bearing, or more commonly sliding contact bearing and slide bearing (in railroading sometimes called a solid bearing, journal bearing, or friction bearing), is the simplest type of bearing, comprising just a bearing surface and no rolli ...
s cannot be used. A tribological coating can be used, for example, where space is limited and access is difficult. In addition, polymer coatings can be customized to suit a wide range of applications, such as particularly high-
temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...
environments or in the
food industry The food industry is a complex, global network of diverse businesses that supplies most of the food consumed by the world's population. The food industry today has become highly diversified, with manufacturing ranging from small, traditional, ...
. The steps to prepare parts for coating with a polymer base are cost-effective compared to other coating options. In addition, the coated end products are consumer-friendly: coated parts are popular because
liquid A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, ...
s such as water and oil bead off when the surface is coated with a
hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, t ...
material. This makes it easier to maintain and clean the end products. Furthermore, the color of the polymer coating can also be adjusted, however with some limitations. The reason for this is that more
pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compo ...
s are needed depending on the color shade, which ultimately influences the coating.


Applications

*
Automotive industry The automotive industry comprises a wide range of companies and organizations involved in the design, development, manufacturing, marketing, and selling of motor vehicles. It is one of the world's largest industries by revenue (from 16 % such ...
: surface coating makes water and oil to bead off, that's why polymer coating is often used for various car accessories. An example is a car paint with ceramic sealing. * Polymer coatings are also used in the
aerospace Aerospace is a term used to collectively refer to the atmosphere and outer space. Aerospace activity is very diverse, with a multitude of commercial, industrial and military applications. Aerospace engineering consists of aeronautics and astr ...
industry. * Other examples of applications include metal, flooring, or medical products, in particular since a polymer coating provides a permanently sterile surface.


Metallization of plastics


Technical process

The application of ultra-fine metal coatings to plastic surfaces is becoming increasingly important. * Dry process: High-vacuum
evaporation Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when h ...
,
cathode A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in whi ...
sputtering In physics, sputtering is a phenomenon in which microscopic particles of a solid material are ejected from its surface, after the material is itself bombarded by energetic particles of a plasma or gas. It occurs naturally in outer space, and ...
, gas and metal plating, and conductive paint spraying. The high-vacuum technique only works if the plastic does not produce gas. In gas plating, unlike the other processes, the metal is formed
in situ ''In situ'' (; often not italicized in English) is a Latin phrase that translates literally to "on site" or "in position." It can mean "locally", "on site", "on the premises", or "in place" to describe where an event takes place and is used in ...
from volatile compounds that are easily decomposed thermally (e.g.,
nickel tetracarbonyl Nickel carbonyl (IUPAC name: tetracarbonylnickel) is a nickel(0) organometallic compound with the formula Ni(CO)4. This colorless liquid is the principal carbonyl of nickel. It is an intermediate in the Mond process for producing very high-pu ...
) by a chemical reaction, and the metal mirror (possibly on a previously stripped plastic surface, e.g., acrylonitrile-butadiene-styrene graft copolymer) is then deposited on the plastic. * Wet process


Plastic coating of materials

The coating process is also called
coating A coating is a covering that is applied to the surface of an object, usually referred to as the substrate. The purpose of applying the coating may be decorative, functional, or both. Coatings may be applied as liquids, gases or solids e.g. Powde ...
technology. Of particular technical importance is the coating of all kinds of materials with plastics. One example is cable sheathing for
electrical cable An electrical cable is an assembly of one or more wires running side by side or bundled, which is used to carry electric current. One or more electrical cables and their corresponding connectors may be formed into a ''cable assembly'', which ...
s or the coating of cutlery baskets in dishwashers.


Technical process

* Fluidized bed sintering * Electrostatic powder spraying, also tribo-coating * Dipping process * Flame spray Theoretically, coatings are also plastic-like coatings. A boundary can be drawn by whether a reaction or crosslinking of the coating takes place (automotive clear coat) or whether a plastic merely melts and solidifies on the surface (vortex sintering with thermoplastics), but the transitions are fluid. As a rule, plastic coatings have significantly higher film thicknesses than conventional paint. For polymer coating, powder coating is commonly used. There are also options for wet coating, vacuum coating,
dip coating image:Dip coating.svg, A schematic of the continuous dip coating process. Roll of coarse cloth Cloth Bath Liquid material Rollers Oven Scrapers Excess liquid falls back A coating remains on the fabric cloth. Dip coating is an industrial ...
, or thermal spraying. The coating can be applied to a polymer or a polymeric material.


References

{{Reflist Coatings