Maya Ellison
Plastic is a widely used material known for its insulating properties. Its ability to efficiently trap heat makes it useful for items like coffee cup sleeves. However, the same insulating property can be detrimental in electronic devices, leading to overheating. Traditionally, plastics have been considered poor conductors of heat due to the tight binding of their molecules, which hinders the transfer of thermal energy. Recent advancements by engineers at MIT have created a polymer thermal conductor that can dissipate heat, offering a potential solution for self-cooling electronic casings. This innovative plastic material challenges the conventional understanding of plastic as solely a heat insulator, showcasing its versatile potential in various applications.
| Characteristics | Values |
|---|---|
| Plastic's ability to insulate heat | High |
| Plastic's ability to conduct heat | Low |
| Plastic's molecules | Tightly bound together |
| Plastic's electrons | Very few free electrons |
| Plastic's use cases | Cookware, dishes, bowls, coffee cup sleeves, laptop and mobile phone casings, electrical components and systems |
| MIT's polymer's ability to conduct heat | 10 times more than most commercially used polymers |
| MIT's polymer's ability to conduct heat | 300 times more than ordinary plastics |
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What You'll Learn
Plastic cookware is safe to use as it doesn't conduct heat well
Plastic is a poor conductor of heat, which makes it a good insulator. The molecules inside plastic are tightly bound together, requiring a lot more energy for them to move and vibrate. This is why plastic cookware is safe to use—it doesn't let heat flow through it easily and protects from heat transfer. Plastic cookware handles, for example, remain cool despite being attached to a hot pan.
However, some plastics can be engineered to conduct heat. A team of engineers at MIT has developed a polymer thermal conductor—a plastic material that works as a heat conductor, dissipating heat rather than insulating it. This discovery could lead to self-cooling casings for electronics.
While plastic cookware may be safe due to its poor heat conduction, it is important to consider other factors when choosing cookware. For example, stainless steel is a preferred material for cookware because it is durable, attractive, and dishwasher, oven, and broiler safe. It also does not react with acidic or alkaline foods and will not discolour or impart a metallic flavour. However, stainless steel is a poor conductor of heat, so it is often impact-bonded with aluminium to improve its conductivity.
Other materials used for cookware include carbon steel, which is widely used as the core metal for enameled cookware, and cast iron, which is also a poor conductor of heat. Copper is the best heat conductor of any material used to make cookware, but it is more expensive and requires more maintenance.
In summary, plastic cookware is safe to use because plastic is a poor heat conductor, but there are a variety of other materials to consider when choosing cookware, each with its own advantages and disadvantages.
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Plastic is a poor heat conductor due to its molecular structure
The conductivity of a substance depends on the number of free electrons in the outer shell of its atoms. Metals, for example, have a high conductivity due to their abundance of free electrons, which facilitates the easy flow of electricity and heat. In contrast, plastics have few or no free electrons because their molecules are composed of long chains of carbon and hydrogen atoms. This structural characteristic contributes to their poor electrical and thermal conductivity.
While traditional polymers are known for their insulating properties, engineers at MIT have recently developed a polymer thermal conductor that can dissipate heat. This novel plastic material can conduct heat 10 to 300 times more effectively than ordinary plastics. However, it is important to note that this heat conduction occurs primarily along the length of each polymer chain, rather than between them, due to weak Van der Waals forces.
The development of plastic conductors has been achieved by mixing plastics with a high concentration of stringy carbon black and a coking compound. Additionally, introducing a π-conjugated system into the polymer structure can enhance its electrical conductivity by forming a system of overlapping π electron systems. These advancements in plastic conductors have potential applications in electronics, such as self-cooling casings for laptops and mobile phones.
In summary, plastic's poor heat conduction is a direct result of its molecular structure, where tightly bound molecules hinder the transfer of thermal energy. However, recent innovations in polymer science have led to the creation of plastic conductors, showcasing the potential for plastics to transcend their traditional insulating roles and find new applications in thermal management.
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Some plastics have higher thermal conductivity than others
Plastics are typically good insulators, which means they can efficiently trap heat. This makes them useful for things like coffee cup sleeves. However, this insulating property is less desirable for products such as plastic casings for laptops and mobile phones, which can overheat due to the trapped heat.
Engineers at MIT have developed a polymer thermal conductor—a plastic material that works as a heat conductor, dissipating heat rather than insulating it. This new polymer can conduct 10 times as much heat as most commercially used polymers, and up to 300 times as much heat compared with ordinary plastics. The lightweight and flexible material could lead to self-cooling casings for common electronics.
The thermal conductivity of plastics varies. While unfilled thermoplastics have a thermal conductivity of around 0.2 W/mK (Watts/meter-°Kelvin), most thermally conductive plastic compounds have 10 to 50 times higher conductivity (1-10 W/mK). Some companies offer products with even higher thermal conductivities, ranging from 10-100 W/mK.
The thermal conductivity of plastics depends on various factors, including the type of polymer and the presence of fillers. For example, polyurethane and polystyrene, two common types of plastic used for everyday household items, have lower levels of thermal conductivity. In contrast, certain synthetic polymers have high conductivity traits and can act as electrical conductors.
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MIT has engineered a plastic that conducts heat
Plastic is generally a good insulator of heat. The molecules inside plastic are tightly bound together, which makes it difficult for heat—generated by molecules vibrating and colliding into each other—to flow through it.
However, in 2018, engineers at MIT developed a polymer thermal conductor—a plastic material that, counterintuitively, works as a heat conductor, dissipating heat instead of insulating it. The new polymers, which are lightweight and flexible, can conduct 10 times as much heat as most commercially used polymers, and up to 300 times as much heat as ordinary plastics.
MIT's polymer thermal conductor is made of polythiophene, a type of conjugated polymer commonly used in many electronic devices. To create this plastic, Xu, Chen, and members of Chen's lab teamed up with Gleason and her lab members to develop a new way to engineer a polymer conductor using oxidative chemical vapour deposition (oCVD). This technique involves directing two vapours into a chamber, where they interact and form a film. The reaction creates rigid chains of polymers, as opposed to the twisted, spaghetti-like strands found in normal polymers.
The MIT team's polymer film is two orders of magnitude more thermally conductive than most polymers and is also more conductive than steel and ceramics. The researchers observed that the films exhibiting better heat conduction consisted of nanofibers with less randomly coiled chains, as opposed to those in common polymers, which resemble tangled spaghetti.
The development of this plastic has promising applications, such as providing self-cooling casings for common electronics like laptops and mobile phones, which often overheat due to the insulating properties of plastic.
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Plastic is a good electrical insulator
The tight molecular bonds in plastic make it difficult for electricity to flow through it. This is in contrast to metals, which have free-moving electrons that are only flimsily attached to their atoms, enabling them to easily conduct electricity.
As a good electrical insulator, plastic is often used to cover appliances, especially electrical ones, to prevent electric shocks. For example, electrical plugs are made of plastic. Similarly, plastic can be used to coat wires to provide protection from electric currents. The density of the plastic used for coating needs to be appropriate for the strength of the electric current.
While traditional polymers are electrically insulating, researchers at MIT have developed a new polymer that conducts heat. This polymer, known as polythiophene, can dissipate heat in one direction along the length of each polymer chain. However, this plastic is still an electrical insulator as it cannot transfer heat between polymer chains due to weak Van der Waals forces.
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Frequently asked questions
Yes, plastic is a good heat insulator. Its molecules are tightly bound together, making it difficult for heat to pass through. This is why plastic cookware stays cool to the touch and plastic dishes and bowls don't get too hot in the microwave.
Plastic has very few free electrons, which means thermal conduction cannot take place. For thermal conduction to occur, molecules need to vibrate or collide with each other to transfer thermal energy. This requires a lot of energy in plastic because its molecules are so closely bound together.
Plastic is often used as an insulator in everyday items such as coffee cup sleeves, cookware, dishes, bowls, and electrical components. It is also used as a casing for laptops and mobile phones, although these can overheat because the plastic traps the heat produced by the devices. Engineers at MIT have developed a plastic polymer that conducts heat to help with this problem.
