Not all plastics have the same level of harm on the environment. Thermoset plastics are strong and durable, making them difficult to recycle compared to thermoplastics. Additionally, there is a Resin Identification Code (RIC) that determines which plastics can be recycled and how. Lastly, some plastics contain chemicals, like chlorine, that can be toxic to the surrounding environment.
In 1907, a Belgian chemist named Leo Baekeland beat chemist James Swinburne to the patent office in Scotland by just one day. There, Baekeland patented a material called Bakelite, which was the world’s first fully synthetic plastic. It served as an important precursor to the types of plastic we use today. From food containers and baby bottles to electronic chip carriers, plastic is everywhere. The market for plastic has never been larger, especially during the Covid-19 pandemic where synthetic polymers and common plastics played a pivotal role in the medical industry. Millions of plastic gloves and masks were used daily.
It’s reasonable to assume that each of us contributes to a significant amount of plastic waste throughout our lives. (Photo Credit: Farantsa/Shutterstock)
Plastic is not entirely evil in the world, but with its abundance, what do we do with all the plastic once we’re finished with it?
What Is Plastic?
To understand the fate of plastic as waste, we need to understand its chemical composition.
Plastic is a polymer, which means it is made up of small chemical units called monomers that are linked together to form a large molecule, the polymer. These monomers are connected through covalent bonds. It’s helpful to think of a monomer as a brick, and multiple bricks are used to construct a house, which represents the polymer. However, not all plastics are the same type of polymer. There are two main types: thermoset plastics and thermoplastics. The difference lies in their chemical and physical properties.
Polypropylene, a plastic made up of multiple monomer units of Propene. (Photo Credit: Danijela Maksimovic/Shutterstock)
Thermoset plastics are produced through liquid molding processes. Polymers and other substances are heated to a liquid state, and as the mixture cools in the mold, it solidifies into a thermoset plastic. This process involves a chemical reaction called cross-linkage, which helps the polymers withstand high temperatures. Examples of thermoset plastics include polyester, polyimides, and polyurethane. However, these plastics cannot be recycled due to their cross-links. In contrast, thermoplastics are susceptible to heat and can be melted when exposed to high temperatures after the curing process. This makes them more recyclable. Polyethylene is a common thermoplastic.
What Happens To All The Plastic Once We’re Done With It?
A recycling symbol made from plastic bottles, which ironically are rarely recycled. (Photo Credit: Mykolastock/Shutterstock)
The answer is simple: recycling
In reality, the issue with plastic is more complex than what meets the eye. The main problem is that plastic cannot be transformed into another substance. While it is technically possible to recycle plastics into fuel or oil, this process results in the release of toxic pollutants, which is a lose-lose situation.
Most plastics are not biodegradable and break down into smaller pieces called microplastics, rather than simpler organic or biological materials. To prevent the formation of microplastics, the ideal solution is to recycle plastics. However, there are many challenges that arise when attempting to scale up plastic recycling.
Plastics and plastic objects are assigned a Resin Identification Code (RIC) to identify the type of plastic used. Based on this code, plastics can belong to one of seven classes. RIC Classes 1 and 2 can be recycled, while Classes 3-7 may be recyclable depending on your location.
There are additional complications with specific cases like two-layered objects, such as a coffee cup, which make plastic recycling more difficult. Plastic fused to another material, like paper, cannot be recycled without separating and processing the materials.
Furthermore, some plastic items can only be recycled a limited number of times because the monomeric chains that make up the plastic reduce in length with each recycling process. This directly impacts the quality and strength of the recycled plastic.
Interestingly, most recycled plastic is reinforced with new or “virgin” plastic to compensate for the loss of quality during recycling. This contradicts the purpose of recycling, which is to use less plastic. One may question if this can truly be considered recycling at all.
So, not all types of plastic are necessarily harmful to the environment. RIC Class 1 and 2 plastics are extensively recycled and are less likely to contribute to the production of microplastics. They are commonly used to make simple single-layered products like water bottles.
Classes 3-6 are more difficult to judge as their recyclability depends on location and the processes required can be more complex. Class 7 plastics are particularly challenging to recycle as they do not fit into any of the previous six classes and their composition is often unknown.
In conclusion, certain types of plastics, like Polyvinyl chlorides (PVCs) and Polystyrenes, pose more danger than others. The recycling processes for PVCs aim to remove hazardous levels of chlorine and additives, as PVC has been classified as a carcinogen by the World Health Organization.
Every single piece of plastic will eventually break down into microplastics. The real issue lies in the lack of plastic recycling. Only 9% of plastic worldwide is actually recycled. We need to find a better solution to increase the amount of plastic being recycled. Without a solution, it doesn’t matter what type of plastic is being produced because most of it will still end up as microplastics since it won’t be recycled in the first place. However, there is some hope. Scientists and engineers are working hard to create new bioplastics made from renewable and biodegradable materials like vegetable oil, yeast, or corn. These bioplastics can biodegrade, offering a positive outlook for plastic management in the future.