If someone asked you to define plastic, what would be your answer? If you are like most people, you think of plastic in terms of a single material that may have different properties depending on how it’s made. You would only be partially correct. Plastics do have different properties, but that is because there are different kinds of plastics. Plastic isn’t just a single material.
The word ‘plastic’ implies plasticity, which is to say a material that can be stretched, molded, bent, etc. All plastics have that in common. Yet not all materials that demonstrate plasticity are necessarily plastic. Sound confusing? That’s because it is. Perhaps reading this entire post will give you a better understanding of the topic.
1. Plastics Are Polymer Chains
There are different types of plastics classified as both synthetic and natural. At the core of each one is the polymer chains that make up its form. Polymers are long chains of molecules or macromolecules connected like cars on a train. The more molecules in the chain, the larger the polymer.
Most plastics are made with heavy molecules. Those molecules are constructed using multiple monomers bonded together. Combining multiple monomers creates a polymer. Multiple polymers in a long chain are the building blocks of plastics. You can manipulate the properties of a plastic product by designing polymer chains accordingly.
2. How Plastics Are Made
The details of how plastics are made change slightly from one plastic to the next. But all plastic production follows the same basic model. Given that the vast majority of plastics are derived from petroleum, discussing how petroleum becomes plastic should offer sufficient explanation.
Petroleum is oil. It is taken out of the ground and sent to processing plants where it is turned into a variety of products. During processing, the individual components in the oil are separated. Some of those components are drawn off and used to make plastic.
First, the components are purged of contamination. Next, they are introduced to a number of chemicals at a certain temperature and pressure. An ensuing chemical reaction causes monomers to form polymers and polymers to form long chains. Combine those chains together and you have a plastic material.
3. Polymer Chains Are Tough
The thing about polymer chains is that they are tough. It is extremely difficult to break the bonds that hold them together, which is why plastic is such a durable material. But that’s also why plastic does not easily decompose. Nature has a tough time breaking polymer bonds without a little help.
The one advantage of bioplastics is that the materials they are made from naturally decompose on their own. This suggests that bio plastics should not hang around in landfills as long as their synthetic counterparts. But by the same token, bioplastics degrade more quickly over time.
4. Plastics and Recycling Numbers
By now, you might be wondering about those recycling numbers that appear on so many plastic products. According to Seraphim Plastics, a Tennessee industrial scrap plastic recycler, those numbers have but one purpose: to tell recycling companies what type of plastic they are dealing with.
Why do they need to know this? Because different types of plastics are recycled in different ways. Some are not recycled easily enough to make them profitable, so they are discarded rather than processed. The numbers simply make it easier for recycling companies to identify the materials they are working with.
Plastic is an interesting material. But it is not just one material, it is many. Plastics can be both synthetic or natural, and their properties can vary substantially from one type to the next.