Alexei Volkov
Plastic is a type of synthetic polymer with a large molecular mass and a mostly linear structure. It is derived from oil, petroleum, or bio-based sources and is composed of long chains of chemically bonded molecules or monomers. Plastics are a subset of polymers, meaning that all plastics are polymers, but not all polymers are plastics. Polymers are materials composed of repeating chains of individual atoms or molecules and can be natural or synthetic. They play an essential role in everyday life and can be found in a wide range of applications, from medicine to automobiles to our homes.
| Characteristics | Values |
|---|---|
| Definition | A polymer is a substance composed of macromolecules. |
| Macromolecule | A molecule of high relative molecular mass, the structure of which essentially comprises the multiple repetitions of units derived from molecules of low relative molecular mass. |
| Monomers | Monomers are small molecules that constitute polymers. |
| Plastic | Plastic is a specific type of synthetic polymer with a large molecular mass and a mostly linear structure. |
| Plasticizers | Plasticizers are small molecules that are added to polymers to increase flexibility and modify the glass-transition temperature. |
| Glass-Transition Temperature (Tg) | The glass-transition temperature is a crucial physical parameter for polymer manufacturing, processing, and use. Below Tg, polymers are brittle and glassy, while above Tg, they become rubbery and viscous. |
| Natural Polymers | Examples include silk, wool, DNA, cellulose, proteins, and natural rubber. |
| Synthetic Polymers | Examples include nylon, polyethylene, polyester, Teflon, epoxy, and polypropylene. |
| Environmental Impact | Synthetic polymers derived from petrochemical products contribute to rising global temperatures and environmental deterioration due to slow biodegradability. |
| Recycling | Plastics can be recycled by remelting and fabricating used plastic into new items, but additives may cause issues in recycled products. |
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What You'll Learn
Plastic is a type of synthetic polymer
A polymer is a substance or material that consists of very large molecules or macromolecules. These macromolecules are made up of repeating subunits derived from one or more types of simple molecules called monomers. Polymers can be natural or synthetic. Natural polymers include proteins, DNA, cellulose, wool, and rubber, while synthetic polymers include nylon, polyethylene, polyester, and epoxy.
Plastic is a specific type of synthetic polymer with a large molecular mass and a mostly linear structure. They are made from molecules derived from oil, petroleum, or bio-based sources. The first synthetic plastic, known as Bakelite, was created in 1909 for telephone and electrical components. Plastics are a subset of polymers, meaning that all plastics are polymers, but not all polymers are plastics. For example, natural polymers such as cellulose, proteins, and cotton are not considered plastics.
Plastics are created by combining different polymers to form long chains of molecules. The resulting plastic polymers can be classified by their chemical synthesis processes, such as condensation, polyaddition, and cross-linking, or by their physical properties, such as hardness, density, tensile strength, and thermal resistance. They can also be classified as thermoplastics or thermosets based on their ability to melt and reform. Thermoplastics, which include commonly used plastics like polyethylene (PE) and polypropylene (PP), can be heated and reformed multiple times, making them recyclable. On the other hand, thermosets, such as epoxy resin and Bakelite, can only melt and take shape once; when reheated, they decompose instead of melting.
Plastics have become an integral part of our lives, with applications in medicine, automobiles, and homes. However, they also present environmental challenges. The production of synthetic polymers, including plastics, relies heavily on petrochemical products, contributing to rising global temperatures. Additionally, the slow biodegradability of plastics often leads to environmental deterioration and harm to ecosystems. Efforts are being made to address these issues, such as developing biodegradable bio-based polymers and technologies to remove plastic waste from marine ecosystems.
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Plasticizers increase polymer flexibility
Plastic is a specific type of polymer made up of long chains of polymers. Polymers are chemical compounds with molecules bonded together in long, repeating chains. They are composed of very large molecules known as macromolecules, which are made up of multiple repetitions of units derived from molecules of low relative molecular mass.
Plasticizers are substances added to polymers and plastics to make them softer, more flexible, and to increase their plasticity. They are added to plastics like PVC to make them suitable for products such as vinyl flooring and plumbing. Plasticizers are also added to concrete to make it more fluid and workable, reducing the amount of water required.
The inclusion of plasticizers increases polymer flexibility by lowering the glass transition temperature (Tg) and reducing interchain interactions. Below Tg, polymers are brittle and glassy, but above Tg, they become rubbery and viscous. Plasticizers create gaps between polymer chains, allowing for greater mobility and fewer interchain interactions.
The molecules of plasticizers can also influence the mobility of the polymer chain. For example, if a plasticizer forms hydrogen bonds with hydrophilic parts of the polymer, the free volume can be decreased. The effect of plasticizers on the elastic modulus depends on both temperature and plasticizer concentration. At a certain concentration, known as the crossover concentration, a plasticizer can decrease the modulus of a material, while the material's glass transition temperature will decrease at all concentrations.
Different types of plasticizers are used for specific purposes. For instance, phthalates are used for flexibility in plastics, dicarbonates are used for shaping PVC at lower temperatures, and phosphates are used to make materials flame retardant.
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Plastics are derived from oil
Plastic is a synthetic polymer derived from crude oil, natural gas, or coal. It is made up of polymeric resin often mixed with additives to achieve specific properties. The main ingredient in most plastic materials is a derivative of crude oil, which is further decomposed to form ethylene and propylene, the raw materials for plastics. This process involves separating the various components of petroleum using their different boiling points.
Crude oil, also known as petroleum, is formed from animal and plant matter subjected to intense heat and pressure underground over millions of years. While most plastics are derived from fossil fuels, a small percentage (about 1-6%) is classified as ""biobased," made from renewable resources such as carbohydrates, starch, vegetable fats and oils, and bacteria. These bioplastics are created by extracting and dissolving sugar from plants like corn, beets, or potatoes and combining them with other materials to form polymers.
The production of synthetic plastics from crude oil is favored due to the ease of manufacturing. However, the growing demand for limited oil reserves has spurred the development of newer plastics from alternative sources. For instance, vegetable oil has been found to be suitable for making polyurethane, but its environmental impact, including deforestation and greenhouse gas emissions, is a concern.
Plastics derived from crude oil contribute significantly to environmental challenges. Their production relies heavily on petrochemical products, which drive up global temperatures. Additionally, the slow biodegradability of synthetic plastics often leads to ecosystem deterioration and threats to the global food chain. As a result, there is a growing focus on reducing the environmental impact of these plastics and developing more sustainable alternatives.
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Plastics are recyclable
Plastic is a specific type of polymer, comprised of a long chain of polymers. Polymers are chemical compounds in which molecules are bonded together in long, repeating chains. Plastics are a specific type of synthetic or semi-synthetic polymer. They are made from molecules derived from oil, petroleum, or bio-based sources, which are combined to create different polymers.
The most widely recycled plastic in the world is PET, which is mostly found in plastic bottles. PET can be recycled into fashion items like polar fleece clothes, backpacks, and carpets. PET can also be recycled into PET bottles, again and again. Another easily recyclable plastic is HDPE, which is accepted at most recycling centers worldwide.
However, some plastics are incredibly hard to recycle, including crisp packets, salad bags, plastic wrap, bioplastics, composite plastic, plastic-coated wrapping paper, and polycarbonate. Some plastics are never recycled, such as plastics number 6 and 7. The recyclability of plastic types depends on how they are made; thermoset plastics contain polymers that form irreversible chemical bonds and cannot be recycled, whereas thermoplastics can be remelted and remolded.
The disposal of plastics presents a significant environmental challenge. Due to their slow biodegradability, synthetic polymers often cause environmental deterioration after disposal, harming ecosystems and threatening the global food chain. The disposal of plastics in landfills and dumps contributes to these issues, as they emit climate-warming methane gas, attract insects and scavenging animals, and leach toxic chemicals. A growing amount of plastics are sent to incinerators, which release toxic chemicals and cause serious health problems and greenhouse gas emissions.
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Plastics are classified by their physical properties
Plastics are a type of synthetic or semi-synthetic polymer. They are composed of very large molecules, or macromolecules, that are constituted by many repeating subunits derived from one or more species of monomers. The defining characteristic of plastics is their plasticity, which allows them to be moulded, extruded, or pressed into a diverse range of solid forms.
Plastics are 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. They can also be classified by the chemical processes used in their synthesis, such as condensation, polyaddition, and cross-linking.
Plastics can also be classified by their physical properties, which include:
- Hardness
- Density
- Tensile strength
- Thermal resistance
- Glass transition temperature
The glass transition temperature (Tg) is a crucial physical parameter for polymer manufacturing, processing, and use. Below Tg, polymers are brittle and glassy, whereas above Tg, polymers are rubbery and viscous. The glass transition temperature may be engineered by altering the degree of branching or crosslinking in the polymer or by the addition of plasticizers.
Another way to classify plastics is by the degree to which the chemical processes used to make them are reversible or not. Thermoplastics do not undergo chemical change when heated and can be moulded repeatedly. Thermosets, or thermosetting polymers, can melt and take shape only once: after they have solidified, they stay solid and retain their shape permanently.
Plastics can also be classified as commodity plastics or engineering plastics. Commodity plastics are primarily chosen for their low cost and ease of manufacturing, while engineering plastics can compete with die-cast metals in plumbing, hardware, and automotive applications.
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Frequently asked questions
A polymer is a substance composed of macromolecules. These macromolecules are multiples of simpler chemical units called monomers. Polymers can be natural or synthetic. Examples of natural polymers include DNA, proteins, cellulose, wool, and silk. Synthetic polymers include polyethylene, nylon, and polyester.
Plastic is a specific type of synthetic polymer. It is derived from oil, petroleum, or bio-based sources. Plastic is a polymer that is typically characterised by a large molecular mass and a mostly linear structure.
Yes, plastic is a type of polymer. All plastics are polymers, but not all polymers are plastics.
