Alexei Volkov
Plastics are made from oil, a carbon-rich raw material, and are classified by their chemical structure, with important groups including acrylics, polyesters, silicones, polyurethanes, and halogenated plastics. The chemical process used to create plastics involves converting raw materials into monomers, such as ethylene, propylene, and butene, which are then linked together through polymerisation to form polymers. Most plastics are chemically inert and do not react with other substances, which is why they are so widely used in products like toys, cups, bottles, utensils, and even medical implants. However, this chemical inertness also contributes to the environmental problem of plastic waste, as plastics do not decay. Microplastics, the breakdown of larger plastics into tiny pieces, have been found in almost every ecosystem on the planet, including the human body, and can release or be covered in harmful chemicals like PFAS.
| Characteristics | Values |
|---|---|
| Raw materials | Crude oil, natural gas, and coal |
| Production process | Extraction, refining, distillation, polymerization |
| Examples of polymers | Polyethylene, polystyrene, polyvinyl chloride |
| Examples of commodity plastics | Polyurethanes (PURs), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC) |
| Examples of thermosets | Epoxy resin, polyimide, Bakelite |
| High-performance plastics | Aramids, Ultra-high-molecular-weight polyethylenes (UHMWPE), Polyetheretherketone (PEEK), Polyetherimide (PEI) |
| Environmental impact | Pollution, microplastics, PFAS, BPA |
| Advantages | Energy efficiency, lightweight, affordability, durability, versatility |
Explore related products
What You'll Learn
Plastic's chemical structure
Plastic is a polymeric material that can be moulded or shaped, often by the application of heat and pressure. The properties of plastics are determined by their chemical structure, which can be modified through the use of additives.
Plastics are polymers of very high molecular mass. Polymers are macromolecules that are based on a structure built up, chiefly or completely, from a large number of similar structural units bonded together. These structural units are often called "chains" and consist of repeating units, similar to links. Polymerisation is a process in the petroleum industry where light olefin gases (such as ethylene, propylene, and butylene) are converted into higher molecular weight hydrocarbons (polymers). This happens when monomers are chemically bonded into chains.
There are two different mechanisms for polymerisation: addition polymerisation and condensation polymerisation. In addition polymerisation, one monomer connects to the next one (dimer) and the dimer to the next one (trimer) and so on. This process is known as chain-growth polymers as it adds one monomer unit at a time. Common examples of addition polymers are polyethylene, polystyrene, and polyvinyl chloride. In condensation polymerisation, two or more different monomers are joined by the removal of small molecules such as water.
Plastics can be classified by the chemical structure of the polymer's backbone and side chains. Important groups classified in this way include acrylics, polyesters, silicones, polyurethanes, and halogenated plastics. They can also be classified by the chemical processes used in their synthesis, such as condensation, polyaddition, and cross-linking. Additionally, plastics can be categorised as semi-crystalline or amorphous based on the organisation of their molecular structure. Semi-crystalline polymers such as polyethylene will undergo a distinct melting transition and have a melting point (Tm). Amorphous polymers, such as polystyrene, will not truly melt but will soften as they are heated above their glass transition temperature (Tg).
Plastic Shields vs Masks: Which Offers Better Protection?
You may want to see also
Explore related products
Plastic's chemical synthesis
Plastic is a synthetic or semi-synthetic material that is mainly synthesized by the polymerization and polycondensation of different monomeric components. The process of plastic synthesis involves several steps, starting with the extraction of raw materials, which are mostly crude oil and natural gas, but also coal. These raw materials are then refined and transformed into different petroleum products through a process called distillation. During distillation, the heavy crude oil is heated in a furnace and separated into lighter components called fractions. One of these fractions, naphtha, is crucial for making plastic.
The next step in plastic synthesis is polymerization, where light olefin gases (such as ethylene, propylene, and butylene) are converted into higher molecular weight hydrocarbons (polymers). This process involves chemically bonding the monomers into chains. There are two types of polymerization mechanisms: addition polymerization and condensation polymerization. In addition polymerization, monomers are added one at a time to form chains, while in condensation polymerization, two or more different monomers are joined together by removing small molecules like water. The polymerization process results in the formation of thick, viscous substances called resins, which are used to make plastic products.
Plastics can be classified in several ways, including the chemical structure of their backbone and side chains, the chemical processes used in their synthesis, and their physical properties. Important groups of plastics based on chemical structure include acrylics, polyesters, silicones, polyurethanes, and halogenated plastics. In terms of synthesis, plastics can be categorized into condensation, polyaddition, and cross-linking types. Plastics can also be classified as thermoplastics or thermosets based on whether they can undergo repeated molding or only take shape once, respectively.
The development of plastic synthesis has had a significant impact on various industries, including packaging, agriculture, construction, consumer goods, and healthcare. However, the widespread use of plastic has also led to environmental concerns, with a particular focus on the issue of plastic pollution. Efforts are currently being made to address this problem, including the development of biodegradable plastics and the creation of a global treaty on plastic pollution.
How to Bond Epoxy Resin to Plastic
You may want to see also
Explore related products
Plastic's chemical properties
Plastics are typically classified by the chemical structure of the polymer's backbone and side chains. Important groups classified in this way include the acrylics, polyesters, silicones, polyurethanes, and halogenated plastics. The polymer is often paired with other materials, or additives, which are added during processing and manufacturing. These additives include plasticizers, colourants, reinforcements, and stabilisers.
Plastics can also be classified by the chemical process used in their synthesis, such as condensation, polyaddition, and cross-linking. They can be further classified by their physical properties, including hardness, density, tensile strength, thermal resistance, and glass transition temperature.
Another important classification of plastics is the degree to which the chemical processes used to make them are reversible or not. Thermoplastics, for example, do not undergo chemical change when heated and can be moulded repeatedly. Examples include polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC). Thermosets, on the other hand, can melt and take shape only once. After they solidify, they stay solid and retain their shape permanently. If reheated, thermosets decompose rather than melt. Examples of thermosets include epoxy resin, polyimide, and Bakelite.
High-performance plastics are a category of polymers that exhibit superior properties to commodity and engineering plastics. These plastics can withstand high temperatures, are highly resistant to chemical corrosion and degradation, and have excellent mechanical and electric properties. Examples include aramids, such as Kevlar, Nomex, and Twaron, which are used in the manufacture of body armour and aerospace applications.
Plastics also have chemical additives that can gradually leach out during normal use or improper disposal. These additives can degrade and form other compounds that may be more toxic. Plastic fragmentation can allow these chemical additives to move far from the point of use, potentially having adverse effects on human health and the environment.
The Plastic Lining of Milk Cartons: What's the Deal?
You may want to see also
Explore related products
Plastic's chemical resistance
Plastic is derived from crude oil and natural gas, which are processed to yield useful chemicals, including "monomers" (molecules that are the basic building blocks of polymers). Polymerisation is a process in the petroleum industry where light olefin gases (gasoline) such as ethylene, propylene, and butylene (monomers) are converted into higher molecular weight hydrocarbons (polymers).
Plastics are classified by their chemical structure, the processes used in their synthesis, their physical properties, and their resistance and reactions to various substances and processes, such as exposure to organic solvents, oxidation, and ionizing radiation. For example, thermoplastics do not undergo chemical change when heated and can be molded repeatedly. On the other hand, thermosets can melt and take shape only once; if reheated, they decompose rather than melt.
High-performance plastics are a category of polymers that exhibit superior properties compared to commodity and engineering plastics. These plastics are highly resistant to chemical corrosion and degradation, have excellent mechanical and electric properties, and are lightweight and extremely versatile. Examples include aramids, which are used in body armor, aerospace, and military applications, and Polyetheretherketone (PEEK), a strong, chemical- and heat-resistant thermoplastic used in medical implants and aerospace moldings.
The chemical resistance of plastics is influenced by factors such as temperature, concentration of driving forces, duration, and mechanical load. Different plastics have varying degrees of resistance to different chemicals, and it is important to consider these factors when selecting a plastic for a specific application.
The Difference Between Plastic and Rubber
You may want to see also
Explore related products
Plastic's chemical reversibility
Plastics are classified by their chemical structure, the chemical processes used in their synthesis, their physical properties, and their reactions to various substances and processes. An important classification of plastics is the degree to which the chemical processes used to make them are reversible or not.
Thermoplastics, such as polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC), do not undergo chemical change when heated and can be moulded repeatedly. On the other hand, thermosets, or thermosetting polymers, can melt and take shape only once. After they have solidified, they stay solid and retain their shape permanently. If reheated, thermosets decompose rather than melt. Examples of thermosets include epoxy resin, polyimide, and Bakelite.
In recent years, there has been a significant effort to develop reversible polymerization approaches in controlled polymerization systems. Reversible polymerization typically involves two steps: forward polymerization, which converts small monomers into macromolecules, and depolymerization, which regenerates the original monomers. Recycled monomers can then be repolymerized into new polymers.
Research in this area has led to the development of several reversible polymerization systems, including ring-opening polymerization of 2-allyloxylmethyl-2-ethyltrimethylene carbonate (AOMEC) and vinyl polymerizations of acrylamide monomers. These advancements in reversible polymerization have important implications for plastic recycling and offer new opportunities in polymer science and engineering.
Biodegradable Plastics: Do They Actually Decompose?
You may want to see also
Frequently asked questions
Plastic is made from oil, a carbon-rich raw material. Other raw materials include natural gas and coal.
Plastic is classified by its chemical structure, the process used to create it, and its physical properties. Important groups include acrylics, polyesters, silicones, polyurethanes, and halogenated plastics.
The process of making plastic involves extracting and refining raw materials, polymerisation, and moulding. During polymerisation, hydrocarbon monomers are linked together by a chemical mechanism to produce polymers, which are then moulded into various shapes.
Most plastics are chemically inert and will not react with other substances. This property allows plastics to be used for storing various materials without dissolving.
