Wiktor Wise
Plastics are organic compounds that are generally considered insulators of electricity due to their lack of ionic characteristics. However, it was long believed that plastics could not conduct electricity at all. This notion was challenged when scientists Alan MacDiarmid, Hideki Shirakawa, and Alan J. Heeger discovered that plastics could conduct electricity under certain circumstances. They were awarded the Nobel Prize in Chemistry in 2000 for this discovery. By adding iodine to the polymer, they increased the conductivity of the plastic. This discovery has led to a more nuanced understanding of the conductive properties of plastics, showing that while they may not be good conductors in their pure form, their conductivity can be enhanced through specific modifications.
| Characteristics | Values |
|---|---|
| Conductivity | Poor/Low |
| Free electrons | Few or none |
| Reaction | Non-reactive |
| Melting point | Low |
| Composition | Carbon and hydrogen atoms |
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What You'll Learn
Plastic has a high number of free electrons
Plastic is considered a poor electrical conductor due to its molecular composition. The number of electrons in the outer shell of an atom determines its conductivity. Metal, for instance, is a good conductor because it has a high number of free electrons. Plastic, on the other hand, has molecules made up of long chains of carbon and hydrogen atoms, which results in few to no free electrons. Consequently, electric charges cannot be carried, and hence, there is no electricity conduction.
However, it is important to note that not all plastics are inherently bad conductors. Scientists have discovered that certain plastics, known as structural plastic conductors, can possess conductive properties on their own. These plastics derive their conductive carriers (electrons or ions) from their polymer structure. By introducing a π-conjugated system, the polymer can exhibit overlapping π electron systems, thereby achieving electrical conductivity. This conductivity can be further enhanced through doping, with dopants such as iodine or arsenic pentafluoride, to increase the number of free electrons available for conduction.
The ability to impart conductivity to plastics has led to the development of plastic conductors, which combine the electrical conductivity of metals with the unique properties of plastics. These plastic conductors have found applications in various fields, including electronics and energy storage. For example, conductive plastics can be used to create high-power plastic batteries, high energy density capacitors, and microwave-absorbing materials.
While plastic may have a reputation for being a poor conductor, the development of plastic conductors showcases the potential to enhance its electrical conductivity. Through modifications to its structure and the introduction of dopants, plastic can be transformed from an insulator to a material capable of conducting electricity, thus expanding its utility in a range of technological applications.
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Plastic melts under high current
Plastic is a poor conductor of electricity due to its lack of free electrons. Its molecules are made up of long chains of carbon and hydrogen atoms, which have a low number of electrons in their outer shells. This is in contrast to metals, which have a high number of electrons in their outer shells, facilitating the easy movement of electric charges.
Plastics have a wide range of melting points, and their behaviour during melting varies. Some plastics have a narrow melting range, while others are more forgiving with temperature changes. The melting point of plastic is influenced by factors such as molecular weight, polymer chain length, and the presence of additives. Longer polymer chains and higher molecular weights generally lead to higher melting temperatures, while shorter chains and lower molecular weights can reduce the melting point.
When subjected to a large current, plastic will melt due to the heat generated by the electrical energy passing through it. This is because the electric charges in the current are unable to move through the plastic due to its lack of free electrons. The heat generated by the current can exceed the melting point of the plastic, causing it to soften and eventually melt.
The melting behaviour of plastics is crucial in manufacturing processes such as injection moulding and 3D printing. In injection moulding, melted plastic is injected into a mould under high pressure and then cooled to form the final product. The melt temperature, mould temperature, and barrel temperature all play a role in determining the quality of the final product. Similarly, in 3D printing, achieving the correct melting temperature is essential for producing high-quality prints without issues like poor layer bonding or weak structures.
It is important to note that melting plastic can release fumes, so adequate ventilation or a respirator is recommended when performing such tasks. Additionally, different types of plastics have different melting behaviours, so it is crucial to understand the characteristics of the specific plastic before attempting to melt it.
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Plastic lacks a system of conjugated pi electrons
Plastic is a poor conductor of electricity because it has few or no free electrons. This is due to the molecular structure of plastics, which are made up of long chains of carbon and hydrogen atoms. For a substance to conduct electricity, it must have free electrons that can be employed to carry electric charges.
The number of electrons in an atom's outer shell determines its conductivity. Metals, for example, have a high number of free electrons, allowing them to conduct electricity effectively. In contrast, plastics have a low number of free electrons due to their molecular structure, which hinders their ability to conduct electricity.
While most plastics are inherently non-conductive, there are some types of structural plastic conductors that are conductive on their own. The conductive carriers (electrons or ions) are provided by the polymer structure, and the conductivity of these plastics can be significantly increased by mixing or doping. For example, doped polyacetylene, when mixed with iodine or arsenic pentafluoride and other electron acceptors, can increase its conductivity up to 104Oh-1·cm-1.
The poor electrical conductivity of plastics makes them useful for specific applications. They are commonly used as insulating cable covers and in electronics packaging. Plastic conductors also have a wide range of practical applications, including switches, pressure-sensitive components, connectors, and electromagnetic shields.
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Plastic has few or no free electrons
Plastic is a poor conductor of electricity because it has few or no free electrons. The number of electrons in an atom's outer shell determines its conductivity. Free electrons are used to conduct electricity, and if there are none present, electricity cannot be conducted.
Plastic's molecular structure is made up of long chains of carbon and hydrogen atoms. This composition results in a low number of free electrons available to carry electric charges.
In contrast, metals have a high number of free electrons, making them excellent conductors of electricity. When a large current is passed through plastic, it will melt, further demonstrating its poor conductivity.
However, scientists have discovered that conductive plastic can be created by mixing plastics with a high concentration of stringy carbon black and a coking compound. These plastic conductors combine the electrical conductivity of metals with the unique properties of plastics. To make a polymer electrically conductive, a π-conjugated system must be introduced to form a polymer with overlapping π electron systems. The regular structure of the polymer is crucial, and dopants can be used to enhance conductivity.
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Plastic has poor electrical conductivity
Despite plastic's inherent non-conductive properties, scientists have discovered ways to enhance its conductivity. By introducing a pi-conjugated system, the polymer structure of plastic can exhibit overlapping pi electron systems, enabling it to conduct electricity. This process involves doping the plastic with a high concentration of stringy carbon black and a coking compound. The resulting plastic conductors combine the electrical conductivity of metals with the unique properties of plastics, opening up a range of applications.
One type of plastic conductor is the structural plastic conductor, where the conductive carriers (electrons or ions) are provided by the polymer structure itself. With the right doping agents, such as iodine or arsenic pentafluoride, the conductivity of these plastics can be significantly increased, even reaching the conductivity of metals. These conductive plastics have numerous practical applications, including high-power plastic batteries, high-energy density capacitors, and microwave-absorbing materials.
Another variety of plastic conductor is the composite plastic conductor, which is easy to prepare and highly practical. These materials are used in switches, pressure-sensitive components, connectors, electromagnetic shields, resistors, and solar cells. They also find applications in antistatic additives, anti-electromagnetic screens for computers, and smart windows. The combination of plastic conductors with nanotechnology is expected to revolutionize molecular electronics, leading to faster and smaller computers.
In summary, while plastic is typically known for its poor electrical conductivity due to its molecular structure, advancements in creating plastic conductors have expanded the possibilities for its use in various electrical applications.
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Frequently asked questions
Plastic has few or no free electrons because its molecules are made up of long chains of carbon and hydrogen atoms. The number of electrons in an atom's outer shell determines its conductivity.
The substance's free electrons are used to conduct electricity. If there are no free electrons, there is no electricity conduction.
Plastic will melt when faced with a large electric current.
Yes, scientists have discovered that plastic conductors can be made by mixing plastics with a high concentration of stringy carbon black and a coking compound.
