Omar Khalid
Plastic is a polymeric material that can be moulded or shaped, usually by applying heat and pressure. It is a catch-all term for a range of different chemical substances. Plastics are made from natural materials such as cellulose, coal, natural gas, salt, and crude oil, through a polymerisation or polycondensation process. Crude oil is a complex mixture of thousands of compounds and needs to be processed before it can be used to make plastic. The production of plastics involves the distillation of crude oil in an oil refinery, which separates the heavy crude oil into groups of lighter components called fractions. One of these fractions, naphtha, is crucial for plastic production.
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What You'll Learn
- Plastic is a polymeric material that can be moulded or shaped
- Plastic is derived from crude oil, natural gas, coal, or renewable resources
- Plastic is not sold pure, but mixed with additives
- Plastic is durable and has a slow rate of degradation
- Plastic is not always synthetic, it can be semi-synthetic or natural
Plastic is a polymeric material that can be moulded or shaped
Plastic is a term used to refer to a wide range of different chemical substances. It is a polymeric material that can be moulded or shaped, usually by applying heat and pressure. This property of plasticity, often found in combination with other special properties such as low density, low electrical conductivity, transparency, and toughness, allows plastics to be made into a variety of products.
Plastics are synthetic or semisynthetic organic polymers that always include carbon and hydrogen. They are formed by joining together many monomers, like a long chain of paperclips, to form one long molecule. The monomers can be a range of different compounds, but specific polymers will generally contain monomers of only one or two types.
The two types of plastic are thermoplastics and thermosetting polymers. Thermoplastics can be moulded repeatedly upon heating, while thermosetting polymers solidify into a permanent shape. Thermosetting plastic is relatively straightforward to compound as it remains liquid until it is cured into its final form. For thermosoftening materials, which are used to make the majority of products, the plastic must be melted in order to mix in the additives.
The additives in plastic are intended to improve the lifespan, workability, or appearance of the final item. They can include stabilizers, plasticizers, colourants, fillers, and reinforcements. These additives can affect the chemical composition, chemical properties, mechanical properties, and cost of the plastic. However, many additives in plastics are toxic and may leach into the environment.
Most plastics are produced from petrochemicals, with bioplastics being made from renewable plant materials like cellulose and starch. The production of plastics involves the distillation of crude oil in an oil refinery, which separates the heavy crude oil into groups of lighter components called fractions. One of these fractions, naphtha, is crucial for the production of plastics. Ethylene and propylene are monomers derived from naphtha that are linked together to form long polymer chains.
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Plastic is derived from crude oil, natural gas, coal, or renewable resources
Plastic is a polymeric material that can be moulded or shaped, often in combination with other properties such as low density, low electrical conductivity, transparency, and toughness. Plastics are essentially polymers, composed of various elements such as carbon, hydrogen, oxygen, nitrogen, sulphur, and chlorine. They can also be produced from silicon atom or silicone.
Plastics can be derived from crude oil, natural gas, coal, or renewable resources. Synthetic plastics are derived from crude oil, natural gas, or coal. Crude oil is the principal source of carbon for modern plastic. However, an array of variants are manufactured from renewable materials. The majority of plastic in use today is synthetic due to the ease of manufacturing methods involved in processing crude oil.
Bio-based plastics come from renewable products such as carbohydrates, starch, vegetable fats and oils, bacteria, and other biological substances. They can also be made from waste biomass, animal-waste products, and other renewable resources. In Europe, only a small proportion (about 4-6%) of oil and gas reserves are used for plastic production, with the rest going towards transport, electricity, heating, and other applications.
Hydrocarbons derived from crude oil, natural gas, and coal are used to create plastic. Carbon has a valency of four, meaning it can pair up with four other electrons from any element of the periodic table to form chemical bonds. Hydrogen, on the other hand, has only one electron in its valence shell, so four hydrogen atoms can pair up with a carbon atom to form a CH4 molecule, or methane, the simplest hydrocarbon.
Plastic products are often polymer resins mixed with additives to provide targeted properties such as toughness, flexibility, elasticity, and colour. The type of plastic used in a product can sometimes be identified by looking at the number at the bottom of the plastic container.
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Plastic is not sold pure, but mixed with additives
Plastic is a polymeric material with the capability of being moulded or shaped, usually by applying heat and pressure. This property of plasticity, often found in combination with other special properties such as low density, low electrical conductivity, transparency, and toughness, allows plastics to be made into a variety of products.
However, plastic is not sold as a pure substance. It is mixed with various chemicals and other materials, known as additives, during the compounding stage. These additives are intended to improve the lifespan, workability, or appearance of the final product. They can include substances such as stabilizers, plasticizers, and dyes. The concentrations of most additives are usually low, but they can be added in higher amounts to create Masterbatch products, where they are concentrated but still properly dispersed in the host resin.
The use of additives in plastics is extensive, and they can make up to 70% of the weight of the final product. Additives cover a wide range of chemical classes, including colorants, light stabilizers, antioxidants, plasticizers, flame retardants, and heat stabilizers. In polyvinyl chloride (PVC), used widely for sanitary plumbing, additives can constitute up to 80% of the total volume.
The compounding of plastics involves heating the plastic to between 150-320°C, which turns it into a molten state. However, molten plastic exhibits poor mixing properties, so extrusion equipment is used to supply the necessary heat and mixing to achieve a properly dispersed product.
The additives present in plastics can have negative environmental and health impacts. They can leach out of plastic products and potentially contaminate soil, air, water, and food. This is particularly concerning in the case of microplastics and nanoplastics, which can allow chemical additives to move far from the point of use. Additionally, the presence of additives in recycled plastics can create complications, as they are difficult to remove and can result in inconsistent properties in the final product.
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Plastic is durable and has a slow rate of degradation
Plastic is a polymeric material that can be moulded or shaped, usually by applying heat and pressure. This property of plasticity, along with other features such as low density, low electrical conductivity, transparency, and toughness, allows plastics to be used in a wide range of applications.
The long molecular chains in polymers are what make them strong and durable. These chains consist of carbon as the defining element, almost always combined with hydrogen, and occasionally with other elements such as nitrogen, oxygen, fluorine, and chlorine. The chemical structure of plastics, with these long chains of molecules, is foreign to nature, which is why they are not readily broken down by microorganisms.
While biodegradable plastics do exist, the degradation of plastics in the environment is a significant issue. The rate of degradation varies depending on the type of plastic and the environmental conditions. For example, the average specific surface degradation rate (SSDR) of polylactic acid (PLA), a type of biodegradable plastic, is 7.5 μm year-1 in the marine environment, which is similar to the degradation rates of non-biodegradable plastics like high-density polyethylene (HDPE). In soil conditions, however, the average SSDR of PLA is significantly higher at 21 μm year-1.
The durability of plastics is a double-edged sword. On the one hand, it makes them well-suited for applications where strength and safety are essential, such as in vehicles, drinking and wastewater pipes, medical implants, and buildings. On the other hand, the very durability that makes plastics useful in these applications also contributes to their persistence in the environment, leading to issues such as plastic waste accumulating in oceans and ingested by aquatic species.
Technologies have been developed to both inhibit and promote the degradation of plastics. For example, polymer stabilizers are added to plastics to improve their lifespan and facilitate recycling, while biodegradable additives have been developed to accelerate the degradation of plastic waste. However, despite these advancements, the full decomposition of plastics remains a challenge, and the ideal plastic material that remains durable during usage but decomposes after disposal is yet to be realized.
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Plastic is not always synthetic, it can be semi-synthetic or natural
The word "plastic" comes from the Latin "plasticus" and the Greek "plastikos", both of which mean "capable of moulding". Plastics are synthetic or semi-synthetic organic compounds, which are polymeric materials that can be moulded or shaped, usually by the application of heat and pressure.
While plastic is often used to refer to commonly used disposable items such as bottles, bags, and toys, it is a catch-all term for a range of different chemical substances. Plastics are formed from polymers, which are themselves formed from chemical entities called monomers. Monomers can be a range of differing compounds, but specific polymers will generally contain monomers of only one or two types.
Synthetic plastics are derived from crude oil, natural gas, or coal, while bioplastics are made from renewable plant materials like cellulose and starch. The first fully synthetic plastic was Bakelite, invented by Leo Baekeland in 1906, which was made from phenol and formaldehyde resin. Baekeland was searching for a synthetic substitute for shellac, a natural electrical insulator, to meet the needs of the rapidly electrifying United States.
However, not all plastics are synthetic. Polymers are not always man-made; DNA is an example of a natural polymer, and cellulose and lignin, found in plants, are further examples. The first man-made bioplastic was Parkesine, patented by Alexander Parkes in 1856, which was made from cellulose nitrate.
The distinction between plastic and synthetic materials is important, especially in the context of environmental considerations. Some synthetic materials are biodegradable or can be recycled more easily than traditional plastics, making them a more sustainable option.
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Frequently asked questions
Plastic is a polymeric material that can be moulded or shaped, usually by applying heat and pressure.
Plastics are made from natural materials such as cellulose, coal, natural gas, salt and crude oil. Crude oil is a complex mixture of thousands of compounds, which need to be processed before they can be used to make plastic.
There are two main types of plastic: thermoplastics and thermosetting polymers. Thermoplastics can be moulded repeatedly upon heating, whereas thermosetting polymers solidify into a permanent shape.
Common plastics include polyethylene, polypropylene, polyvinyl chloride (PVC), and polystyrene.
Most plastics are not biodegradable and can take thousands of years to decompose. They can also release toxic gases when burned, so their disposal poses a problem. Recycling of plastics is encouraged to reduce their environmental impact.
