Maya Ellison
Plastic is everywhere, and it comes in many different forms. While there are hundreds of types of plastic, only a handful are commonly used. Plastic is classified into seven categories, each with distinct physical and chemical properties, impacting their use and recyclability. Understanding the different types of plastic is essential for effective recycling and awareness of potential health hazards. This introduction will explore the seven categories of plastic, their unique characteristics, and their applications in daily life.
| Characteristics | Values |
|---|---|
| Number of categories | 7 |
| Types of plastic | Polyethylene Terephthalate (PET), High-Density Polyethylene (2-HDPE), Polypropylene (5-PP), Polyvinyl Chloride (PVC), Polystyrene, Polycarbonate (PC) |
| Plastic classification methods | Chemical process used in synthesis, physical properties, resistance and reactions to substances, qualities relevant to manufacturing or product design |
| Plastic applications | Packaging, plumbing, clothing, food, pharmaceutical, construction, optical devices, household items, business |
| Plastic production in 2018 | 343 million tons |
| Plastic waste in 2018 | 90% of plastic production |
| Plastic waste in oceans | China, Indonesia, Philippines, Thailand, and Vietnam dump more plastic into the sea than all other countries combined |
| Microplastics | Synthetic solid particles or polymeric matrices with a size ranging from 1 μm to 5 mm; dangerous to human health and the environment due to the presence of harmful chemicals |
| Plastic additives | Flame retardants, cadmium, chromium, lead, mercury |
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What You'll Learn
Plastic is classified into seven types
Polyethylene Terephthalate (PET) is the first type of plastic. PET is lightweight, strong, and typically transparent, making it ideal for food packaging, beverage bottles, and fabrics. It is easily recyclable and has excellent chemical resistance to organic materials. Polyethylene Terephthalate is one of the safest options among plastics and is highly shatter-resistant.
High-Density Polyethylene (HDPE) is the second type. HDPE is strong and resistant to moisture and chemicals, commonly used in cartons, containers, pipes, and building materials. It is one of the safer options and is often picked up by recycling programs.
Polyvinyl Chloride (PVC) is the third most commonly produced synthetic plastic polymer. It comes in rigid and flexible forms. Rigid PVC is used in construction materials, doors, and windows, while flexible PVC is applied in plumbing, wiring, and electrical cable insulation. Despite its versatility, PVC is challenging to recycle and should be avoided when possible.
Low-Density Polyethylene (LDPE) is the fourth type of plastic, characterised by low-density molecules, resulting in a thinner and more flexible design. LDPE is commonly used in plastic bags, disposable packaging, and food containers.
Polypropylene (PP) is the fifth type of plastic and is known for its flexibility and durability. PP is stronger than Polyethylene and is widely used in laboratory equipment, automotive parts, and food containers. It is resistant to repeated stress and has excellent heat and acid resistance.
Polystyrene is the sixth type of plastic on the list. It can be solid or foamed and is inexpensive and easy to produce. Polystyrene is found in beverage cups, packing materials, disposable dinnerware, and insulation. It is highly inflammable and dangerous when heated, as it can release harmful chemicals. It is considered one of the worst types of plastics environmentally due to its non-biodegradable nature.
The seventh category is a catch-all for plastics that don't belong in the other six categories or are combinations of multiple types. This group includes items such as eyeglasses, baby bottles, electronics, and clear plastic cutlery. Plastics in this category are typically non-recyclable.
While these seven types are the most common, it is important to note that there are hundreds of types of plastic polymers, and the classification is based on various factors such as chemical structure, physical properties, and manufacturing applications.
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Polyethylene is the most common plastic
Plastic is classified under seven categories, according to the Resin Identification Code (RIC) system introduced by the Society of the Plastics Industry in 1988. The purpose of the RIC system is to "provide a consistent national system to facilitate recycling of post-consumer plastics."
HDPE is strong and resistant to moisture and chemicals, making it ideal for cartons, containers, pipes, and other building materials. Examples of products made from HDPE include milk cartons, detergent bottles, cereal box liners, toys, buckets, park benches, and rigid pipes.
LDPE is formed with both long and short branches in the polymer chains. The presence of these branches keeps the chains from being too tightly packed together, giving LDPE a flexibility that makes it suitable for applications like plastic bags, wire insulation, and plastic wrap. LDPE is highly resistant to most chemicals, including acids, bases, alcohols, aldehydes, ketones, and vegetable oils. It also has very low water absorption.
LLDPE is similar to LDPE but consists of largely linear chains with many short side branches. It is often produced using copolymerization of ethylene with alpha-olefins like 1-butene, 1-hexene, and 1-octene. The characteristics of the finished product can be manipulated through adjustments to the constituent formula.
Polyethylene is a polymer, primarily used for packaging (plastic bags, plastic films, geomembranes, and containers, including bottles, cups, and jars). It is a very durable material that does not easily wear or weaken. Its longevity and durability are so good that many manufacturers describe polyethylene products as maintenance-free. However, continued exposure to sunlight can cause brittleness in polyethylene products over time.
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Plastic is classified by chemical processes
Plastic is a complex material with many different types and classifications. While there are hundreds of types of plastic, only a handful are commonly encountered. In 1988, the Society of the Plastics Industry introduced the Resin Identification Code (RIC) system, which categorised plastic resins into seven groups to facilitate recycling.
Plastics are classified by their engineering behaviour, as well as by the chemical processes used in their synthesis, such as condensation, polyaddition, and cross-linking. They can also be classified by their physical properties, including hardness, density, tensile strength, thermal resistance, and glass transition temperature.
One important classification of plastics is whether the chemical processes used to make them are reversible or not. Thermoplastics, for example, can be moulded repeatedly as they do not undergo chemical change when heated. Examples include polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC). Thermosets, on the other hand, can only take shape once. After solidifying, they retain their shape permanently and decompose if reheated. Examples include epoxy resin, polyimide, and Bakelite.
Plastics can also be classified by their resistance and reactions to various substances and processes, such as exposure to organic solvents, oxidation, and ionising radiation. Some plastics are highly resistant to fatigue, like PP, which is used for living hinges. Polystyrene, another common plastic, is inexpensive and easy to create, but it is highly flammable and dangerous as it can leach harmful chemicals when heated.
Polymer materials can also be classified into three groups based on their reaction to heat: high-quality, non-melting thermosetting materials that harden under thermal treatment or due to a suitable hardener; duroplasts, which include synthetic resins and polyacrylonitrile polymers; and thermoplastics, which become malleable under increasing temperatures and can be reshaped multiple times.
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Plastic is classified by physical properties
Plastic is a term used to refer to a wide range of semi-synthetic or synthetic organic polymers. The term was derived from the Ancient Greek word "plastikos", meaning "capable of being shaped or moulded".
Plastics are classified by their physical properties, including hardness, density, tensile strength, thermal resistance, and glass transition temperature. They can also be classified by the chemical process used in their synthesis, such as condensation, polyaddition, and cross-linking.
Plastics are classified into seven different types, each with distinct characteristics and applications. These seven types of plastic are further categorized by recycling codes, which help identify their specific properties and recyclability.
One of the most common types of plastic is polyethylene, which is classified into three subtypes: high-density, low-density, and linear low-density. High-density polyethylene is strong and resistant to moisture and chemicals, making it ideal for cartons, containers, and pipes. Polyvinyl chloride (PVC) is another widely used plastic, known for its strength and durability. It is commonly used in the construction industry, particularly for pipes and wiring.
Polystyrene is another type of plastic that is inexpensive and easy to produce. It can be found in various products, including beverage cups, insulation, packing materials, and disposable dinnerware. However, polystyrene is highly inflammable and releases harmful chemicals when heated.
Plastics have diverse physical properties, such as being lightweight, durable, flexible, non-toxic, and inexpensive to produce, making them suitable for a wide range of applications. They can be easily moulded into different shapes and sizes, have good impact resistance, and do not rust. However, they may also exhibit poor dimensional stability and be susceptible to deformation.
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Plastic is classified by its reactions to substances
Plastic is a complex material with a wide range of applications. It is classified into seven main types, each with unique characteristics and uses. One way to classify plastics is by their reactions to various substances and processes, such as their exposure to organic solvents, oxidation, and ionizing radiation.
Plastics can be categorized based on their resistance to specific substances. For instance, some plastics are highly resistant to chemicals, while others are susceptible to deterioration when exposed to certain compounds. Polyethylene, for example, exhibits strong resistance to chemicals and moisture, making it ideal for use in cartons, containers, and pipes. On the other hand, polyvinyl chloride (PVC) is challenging to recycle due to the chemicals it contains, and its use should be avoided whenever possible.
The reaction of plastics to heat is another critical factor in classification. Different plastics exhibit varying responses to heat exposure. Some plastics shrink and deteriorate rapidly when exposed to high temperatures, while others are highly heat-resistant and can withstand even extreme temperatures. This property is essential in applications where plastics are used in high-temperature environments, such as in building and construction.
Additionally, plastics can be classified by their reactions to substances used during the manufacturing process. For example, thermoplastics, a type of plastic that includes polyethylene and polystyrene, become malleable when subjected to increasing temperatures. They can be reshaped multiple times and will retain their new shape upon cooling. In contrast, duroplasts, or thermosetting plastics, harden under thermal treatment or due to the action of a hardener. These plastics are classified as high-quality and are often used in applications where heat resistance is crucial.
The classification of plastics by their reactions to substances is essential for understanding their suitability for specific applications. It also helps consumers make informed decisions about the products they purchase, particularly regarding the environmental impact and health hazards associated with different types of plastics.
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Frequently asked questions
Plastic is classified under seven main categories, according to the Resin Identification Code (RIC) system.
The seven types of plastic are: Polyethylene Terephthalate (PET), High-Density Polyethylene (2-HDPE), Polyvinyl Chloride (PVC), Low-Density Polyethylene (LDPE), Polypropylene (5-PP), Polystyrene, and a catch-all category for other types of plastic that don't fall into the previous six categories.
Collectively, Polyethylene is the most common type of plastic in the world. It is classified into three types: High-Density Polyethylene (HDPE), Low-Density Polyethylene (LDPE), and Linear Low-Density Polyethylene.
Plastic can be dangerous to human health and the environment due to the presence of harmful chemicals, especially when heated. Microplastics, in particular, are a major source of pollution and have been found in increasing concentrations in the food chain.
No, not all plastics can be recycled. The recyclability of plastic depends on various factors, including the type of plastic, the presence of additives, and the availability of specialized recycling facilities and technology.
