Chloe Zhang
Plastic is a synthetic or semisynthetic material that uses polymers as its main ingredient. There are hundreds of types of plastic, but only a handful are commonly encountered. Plastic is typically divided into two types: thermoplastics and thermosets. Thermoplastics can be easily deformed and bent upon heating, whereas thermosets cannot be softened again by heating once they are moulded. The majority of plastic that is manufactured is classified as a thermoplastic (80%) and can, therefore, be easily recycled. However, not all plastics are created equal when it comes to the environment, and some types of plastic are more environmentally damaging than others. It is important for consumers to be able to identify the different types of plastic so that they can either avoid certain types or recycle them more effectively.
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What You'll Learn
Thermoplastics and thermosets
There are hundreds of types of plastic, or polymers, but only a few are commonly used. These can be divided into three distinct classes: thermoplastics, elastomers, and thermosets. Thermoplastics and thermosets are two distinct types of polymers with different behaviours under heat.
Thermoplastics
Thermoplastics are polymers that become pliable or mouldable when heated and solidify upon cooling. This process can be repeated multiple times without significant degradation. Thermoplastics soften when heated and can be reshaped or remoulded, making them highly versatile for manufacturing processes like injection moulding, extrusion, and 3D printing. They typically have good impact resistance and mechanical strength, depending on the specific type. Thermoplastics are widely used in consumer goods, packaging, and the automotive industry. They are generally recyclable.
Thermosets
Thermosets are a type of polymer that undergoes a chemical reaction when heated, creating a three-dimensional network of bonded molecules. This process is irreversible, meaning that once the thermoset has been formed, it cannot be melted or reshaped. Thermosets are typically hard and strong, with excellent resistance to heat and chemicals. They are commonly used in applications requiring durable and heat-resistant materials, such as electronics, aerospace, automotive parts, and household appliances. Thermosets are difficult to recycle due to their irreversible curing process.
Examples of Plastics
Some examples of commonly used plastics include:
- Polyethylene terephthalate (PET): Used for food and drink packaging due to its ability to prevent oxygen from spoiling the product and its ability to keep carbon dioxide in carbonated drinks.
- Polyvinyl chloride (PVC): Used in toys, blister wrap, cling wrap, detergent bottles, and medical tubing. However, PVC is considered hazardous due to its potential to leach toxic chemicals.
- Polystyrene: A rigid, low-cost plastic with good insulation properties, commonly used in food packaging, construction, and disposable dinnerware. However, it is not easily recyclable and can leach harmful toxins.
- Polycarbonates (PC): Used for eye protection, such as lenses for sunglasses and sports goggles, as well as in electronics and compact discs (CDs).
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PET, a common plastic for food and drink packaging
Plastic is a complex material with hundreds of types, but only a handful that humans interact with regularly. One of the most common types of plastic is PET, or polyethylene terephthalate, which is used for food and drink packaging. PET plastic is lightweight, strong, and shatterproof, making it ideal for beverage packaging. It is also resistant to chemicals, impact, moisture, and other outside substances, meaning it is unlikely to degrade or leach harmful chemicals into the food or beverage it contains. This makes it a safe option for food and beverage manufacturers.
PET plastic is also versatile and can be easily moulded into various shapes and sizes, making it a popular choice for packaging different types of food and beverages. It is used for everything from salad dressing and peanut butter to honey and polyester clothing. Its ability to prevent oxygen from getting in and spoiling the product inside, as well as keeping carbon dioxide in carbonated drinks, makes it a cost-effective option for manufacturers and consumers alike.
Despite its many advantages, there are some concerns about the environmental impact of PET plastic. While it is one of the most commonly recycled plastics, it does contain some harmful chemicals, such as antimony trioxide, a carcinogen. The longer a liquid is left in a PET container, the greater the potential for the release of these chemicals, especially in warm temperatures. This has led to an increase in the development of refillable bottles, which can be reused many times and are designed to stringent standards to prevent chemical leakage.
To avoid the toxic chemicals found in PET plastic, it is recommended to avoid plastic food and beverage packaging altogether, opting for glass instead. It is also important to avoid high heat, reduce storage times, and never microwave plastic, as this increases the transfer of chemicals from the plastic to food and drinks.
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Polystyrene, a dangerous plastic
Plastic is not just one material, there are hundreds of types, or polymers, of plastic. However, only a handful of these are commonly used. The most common types of plastic are numbered from 1 to 7, according to their recycling codes.
Polystyrene is the sixth type of plastic on this list and is considered a dangerous plastic. It is a very inexpensive resin per unit weight and easy to create, which is why it is so widely used. Polystyrene is also known as Styrofoam, a commercial name for the foam version of polystyrene. It is highly inflammable and can leach harmful chemicals, especially when heated. For this reason, it is dangerous to heat Styrofoam containers in the microwave, as is often done with takeaway containers. Polystyrene is also not biodegradable and is resistant to degradation in the environment. It is often found as litter and can be blown in the wind or float on water, where it may be mistaken for food by birds or marine animals, causing serious health effects.
Polystyrene is a thermoplastic made from styrene, a known carcinogen derived from highly hazardous chemicals, including benzene and ethylbenzene. It is used in food packaging, toys, electronics, and building materials. During production, workers are at risk of exposure to these dangerous chemicals. Polystyrene is often filled with chemical additives to give it physical properties, which can expose consumers to further toxic chemicals. These additives are not chemically bound to the plastic and can migrate or leach out, contaminating drinking water, indoor air, dust, and food.
Polystyrene is also harmful to the environment. Its production relies on dirty fossil fuels and massive energy consumption, contributing to climate change. It is derived from natural gas and oil, whose extraction requires huge amounts of energy and releases large amounts of greenhouse gases. Polystyrene is also difficult to recycle. The only technology that can convert it into anything other than trash is "chemical recycling", which is highly inefficient and polluting. This process uses solvents and high heat to break down plastics, creating a dirty and toxic fuel, as well as toxic emissions and hazardous waste.
Due to the dangers of polystyrene, many countries and regions have banned it, including Canada, Chile, Peru, the European Union, India, New Zealand, and several US states.
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Polyvinyl Chloride (PVC), a toxic plastic
Plastic is not just one material, there are hundreds of types of plastic (polymers) but only a handful that humans interact with regularly. There are seven types of plastic that are commonly known, each with different materials and grades. Some are reusable, while others produce hazardous materials after several uses. Some are easily recyclable, while others need more sophisticated recycling processes.
Polyvinyl Chloride (PVC) is one of the most common types of plastic. It is typically used in toys, blister wrap, cling wrap, detergent bottles, loose-leaf binders, blood bags, and medical tubing. It is also found in upholstery, shower curtains, and school supplies. PVC used to be the second most widely used plastic resin in the world, but the manufacturing and disposal processes have been declared as causes of serious health risks and environmental pollution issues.
PVC is considered the most environmentally damaging plastic and one of the most toxic substances on the planet. The PVC life cycle (production, use, and disposal) results in the release of toxic, chlorine-based chemicals, and it is one of the world's largest sources of dioxins. These toxins build up in water, air, and food chains, causing severe health problems, including cancer, immune system damage, and hormone disruption.
The use of PVC may leach a variety of toxic chemicals such as bisphenol A (BPA), phthalates, lead, dioxins, mercury, and cadmium. Several of these chemicals may cause cancer, allergic symptoms in children, and disrupt the human hormonal system. For example, the release of phthalates is higher for smaller particles and particles with a higher content of plasticizer. The ageing of plastics due to solar radiation can also increase the release of phthalates.
To avoid the dangers of PVC, one can use stainless steel or glass bottles instead of plastic bottles, and purchase toys that are not made of plastic. It is also important to keep indoor rooms well ventilated and to avoid eating food stored or microwaved in PVC plastic wrap.
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LDPE, a safer plastic option for food and drink
Plastic is not just one material, but hundreds of different types, or polymers. Each type of plastic has a unique composition, properties, and applications. Some are safer and easier to recycle than others. LDPE (low-density polyethylene) is one type of plastic that is considered a safer option for food and drink packaging.
LDPE is a type of plastic with a simple chemical structure, making it easy and inexpensive to produce. It is less dense and less crystalline than other types of polyethylene, giving it a thinner and more flexible form. LDPE is commonly used for plastic bags (such as grocery, bread, and frozen food bags), plastic wraps, coatings for paper cartons, beverage cups, squeezable bottles, and food storage containers. It is also used for wire and cable covering.
LDPE is considered a safer option for food and drink packaging compared to other plastics like PVC, which is known to leach harmful chemicals such as BPA and phthalates. LDPE is less likely to leach toxins into food and drinks, making it a preferable choice for packaging consumables. However, some studies have suggested that LDPE may have negative hormonal effects on humans, similar to other plastics like PP and PVC.
While LDPE is a safer option for food and drink, it is not without its drawbacks. One significant disadvantage of LDPE is its difficulty in being recycled. It is not as rigid as other plastics and has a lower tensile strength, making it challenging to recycle. Despite this, LDPE is still easily reusable, making it a more environmentally friendly option compared to single-use plastics.
In summary, LDPE is a safer and more flexible option for food and drink packaging. Its simple chemical structure makes it inexpensive and widely used, especially for consumable products. While it may have some potential negative health effects, it is generally preferred over other plastics that are known to leach harmful chemicals. LDPE's reusability also contributes to its appeal as a more sustainable alternative.
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