Omar Khalid
Plastic is a polymer derived from petrochemicals and is used to make a wide range of products, from clothing to packaging. Grade 8 students can learn about plastics through various hands-on activities and curricula designed to engage and educate them on the topic. These activities can involve examining different plastic objects, understanding plastic properties, and exploring the environmental impact of plastic pollution, including the issue of microplastics in our oceans. By participating in these activities, students will gain a deeper understanding of plastics, their advantages and disadvantages, and the importance of reducing, reusing, and recycling plastic materials.
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What You'll Learn
Plastic types: thermoplastics and thermosetting plastics
Thermoplastics and thermosetting plastics are two different types of polymers with distinct molecular bonds and reactions to heat. They are used in a wide range of applications, from everyday items to specialised equipment.
Thermoplastics are plastics that can be easily deformed or bent when heated and are highly versatile. They have low melting points, and when heated, they can be softened and moulded into almost any shape. Thermoplastics can be reheated, remoulded, and cooled multiple times without changing their chemical composition. Common thermoplastics include PVC and polythene, which are used in plastic bags, bottles, toys, packaging, automotive parts, and textiles. Thermoplastics are also recyclable, making them more environmentally friendly.
Thermosetting plastics, on the other hand, are known for their durability and heat resistance. Once hardened or moulded, they cannot be softened or reshaped by heat. They have high melting points, and once exposed to a certain temperature, their components and physical properties become permanently set. Examples of thermosetting plastics include Bakelite, melamine, and epoxy resin. Thermosetting plastics are commonly used in construction, electrical components, insulators, motor components, and kitchenware. They are valued for their strength and stability but cannot be recycled due to their chemical makeup.
The choice between using thermoplastics or thermosetting plastics depends on the specific requirements of an application. Both types of plastics have their advantages and drawbacks, offering different benefits in terms of flexibility, heat resistance, durability, and recyclability.
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Plastic identification: recycling codes
Plastic is a polymer that can be recycled, coloured, reused, moulded, or drawn into wires or various other shapes. Some plastics have a linear arrangement of units, while others are formed by the cross-linked arrangement of units. Plastic is used in making toys, suitcases, bags, cabinets, brushes, chairs, and tables, among other items. Polythene is a commonly used plastic, employed in the manufacturing of carry bags.
Plastics are broadly categorized into two types: thermoplastics and thermosetting plastics. Thermoplastics are plastics that can be easily bent or deformed when heated. Examples include PVC and polythene. Thermosetting plastics, on the other hand, do not get deformed or softened when heated after being moulded once. Bakelite and melamine are examples of this type of plastic.
Now, let's delve into the recycling codes for plastic identification:
The chasing arrows symbol, widely recognized as the recycling symbol, was created in 1970 to indicate that a product was recyclable. In the 1980s, plastic manufacturers adopted a similar symbol with a number inside, known as the Resin Identification Code (RIC). The RIC informs manufacturers about the specific type of plastic a container is made from. However, it does not indicate whether the product is recyclable. This has led to a common misconception, as consumers often assume that the chasing arrows symbol implies recyclability.
- PET (Polyethylene Terephthalate): This plastic is one of the most widely recycled plastics globally, often used in food containers. Clear PET, in particular, has a high recycling value as it can be turned into new products of similar quality. Look for products packaged in #1 plastics like PET, as they can be widely recycled.
- PP (Polypropylene): PP is a durable plastic that is increasingly accepted for kerbside recycling. It is used in products like food containers and even recycling bins.
- PS (Polystyrene): Polystyrene, commonly known as styrofoam, is challenging to recycle and has been associated with leaching chemicals when heated. It is used in food packaging and comes in two forms: hard, compressed PS and expanded polystyrene (EPS), which is lighter and "puffed." While EPS has limited use in industrial applications, it cannot be recycled for its original purpose.
Recycling symbols are important for identifying how different types of packaging can be recycled. These symbols are found on various items, from soft drink cans to bread bags and plastic toiletry bottles. They indicate whether the packaging will be collected for recycling or if it needs to be taken to a local recycling centre. Additionally, certain symbols indicate compostability rather than recyclability, and these items should be treated differently.
In summary, understanding plastic identification through recycling codes is essential for proper waste management. While the RIC helps identify the type of plastic, it is crucial to learn about the recyclability of specific plastics to ensure responsible recycling practices.
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Plastic properties: flexibility, toughness, etc
Plastic is a polymer that can be recycled, coloured, reused, moulded, or drawn into wires or various other shapes. The properties of plastics vary, and they can be flexible or rigid.
The flexibility of plastics is measured by their flexural modulus, which describes the ability of a material to bend. The higher the flexural modulus, the stiffer the material; the lower the flexural modulus, the more flexible it is. Flexible plastics like polyethylene and polypropylene are different from rigid plastics in that they don't resist deformation as well, but they tend not to break. The ability to deform is what keeps them from breaking. For example, a plastic bag will stretch easily once it has been stretched far enough.
Toughness is a measure of the energy absorption capacity of a material during impacts. Toughness can be measured by striking a small rectangular rod with a pendulum at high speed and measuring the energy absorbed while breaking the specimen. Toughness is also a measure of the energy a sample can absorb before it breaks. Flexible plastics tend to be tougher than rigid plastics, which are more brittle.
Some plastics can be altered with additives called plasticizers to change their stress-strain behaviour. For example, poly(vinyl chloride) (PVC) is a rigid plastic used for water pipes, but with plasticizers, it can be made flexible enough to use for inflatable swimming pool toys.
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Plastic uses: toys, bags, clothing, etc
Plastic is a versatile material that can be moulded, shaped, and formulated for various uses. However, it is essential to recognise the environmental impact of plastic pollution, which has affected wildlife, human health, and contributed to climate change. Here is a detailed look at some common uses of plastic:
Toys
Plastic is widely used in the manufacturing of toys due to its lightweight and durable nature. Injection moulding techniques can create lightweight toys that are easy for children to handle. Plastic toys are also known for their resistance to stains and chemicals, making them easier to clean and maintain. However, some plastic toys may contain bisphenol-A (BPA) and phthalates, which have raised safety concerns. To address this issue, toy manufacturers can utilise formulations that exclude these harmful compounds.
Bags
Plastic bags, particularly single-use shopping bags, have come under scrutiny due to their detrimental environmental impact. They contribute significantly to plastic pollution, with a large percentage ending up in landfills and the ocean. Plastic bags can take up to 1,000 years to degrade, breaking down into microplastics that absorb toxins and continue to pollute the environment. Additionally, plastic bags contain chemical additives associated with negative health effects, including cancers and immune system suppression. Efforts to reduce plastic bag usage include implementing bag ordinances, encouraging the use of reusable bags, and supporting legislation to regulate and reduce plastic production and waste.
Clothing
Synthetic fibres derived from plastic, such as polyester, nylon, and acrylic, comprise about 60% of the material used in clothing worldwide. These fibres offer advantages such as stretch, breathability, warmth, and sturdiness. However, washing synthetic clothing contributes to ocean plastic pollution as tiny plastic fibres are released into the water supply. These fibres are too small to be captured by filters in sewage treatment plants and eventually make their way into rivers or the sea. To mitigate this issue, individuals can opt for natural fibres or buy fewer clothes, but these alternatives may not always be environmentally friendly or accessible to everyone.
Plastic is a versatile material that has found its way into various aspects of our daily lives, from toys and bags to clothing. While plastic offers convenience and functionality, it is crucial to address the environmental and health concerns associated with its use.
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Plastic recycling: why it's important
Plastic recycling is important as it helps to reduce the amount of plastic waste that ends up in our streets, parks, and oceans, and environment. This waste can pose a significant threat to wildlife and the natural world. Recycling plastic helps to keep it in use and out of landfills, reducing the harmful effects of pollution and emissions.
Recycling plastic also contributes to energy conservation. For example, recycling just 10 plastic bottles saves enough energy to power a laptop for over 25 hours. It takes 75% less energy to make a plastic bottle from recycled plastic compared to using new materials. Recycling plastic also reduces the need for new plastic made from raw materials, saving energy and carbon.
The process of recycling plastic transforms it back into valuable resources, helping to build a more sustainable future. Recycled plastic can be used in new ways, such as in carpeting and park benches, and can be incorporated into new products by businesses, reducing their environmental footprint.
Plastic recycling also helps to change our perception of plastic, seeing it less as rubbish and more as something useful. This shift in perspective can lead to a reduction in littering, which is beneficial for the environment and wildlife.
Additionally, plastic recycling is important in addressing the plastic problem we face today. Plastic is a non-biodegradable substance, meaning it does not easily decompose through natural processes. When plastics are burned, they release poisonous fumes, contributing to air pollution. By recycling plastic, we give it a new life and keep it out of the environment.
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Frequently asked questions
Plastic is a polymer that can be recycled, coloured, reused, moulded, or drawn into wires or various other shapes. Plastic was discovered by German chemist Christian Schonbein in 1846.
Depending on physical properties, plastics are divided into two types: Thermoplastic and Thermosetting. Thermoplastics can be deformed easily upon heating and can be bent, whereas Thermosetting plastics cannot be softened again by heating once moulded.
Plastic is everywhere—the soles of your shoes, your pens, rulers, fleecy jackets, and most carpets are all made from plastic fibres. Other examples include plastic toys, suitcases, bags, cabinets, brushes, chairs, and tables.
