Author: Stephane Girois, Ph.D.
Many plastics for many uses
Let’s go back to being a little chemist for a minute to understand what a plastic is. Plastics fall into a much larger category of materials called polymers. Polymers can be found as synthetics like thermoplastics and rubbers; or can be found naturally in your own DNA, and proteins like your hair, wool, silk, or cellulose from trees (which is used to make paper).
The word plastic refers to a broad spectrum of products, typically synthetic (man-made), and are used in everyday life. They are produced in large chemical plants, using mostly fossil oil, and more recently, crops like corn or sugar cane.
Making plastics is like playing with Legos of multiple shapes and colors. Only your imagination is the limit. There are thousands of plastics today, and each was designed to have a particular set of properties and performances, like these examples:
– Transparent or opaque
– Glossy or matte
– Heat, UV, or flame resistant
– Hard or soft at room temperature
– Barrier to oxygen or moisture
– Strong at low temperatures
– Conducting or resistant to electricity
– Resistant to scratches
– Cheap or expensive
– Water repellant
– Food approved
Here is a list of common plastics you might find in your household, along with their typical uses. In some finished products, the plastics number is indicated:
Of course, the reality is even more complex. As you can imagine, most plastic products today are not just made of one plastic but a combination of several. The picture below explains why, for example, milk and juice cartons are not recyclable in many local recycling programs. Separating layers is very costly.
Plastics are rarely pure in composition and always contain other chemical additives used to improve the transformation process and the performance. Additives content can vary from a few percent to 80%. As will be discussed in a later article, plastic diversity in type and composition is the main reason why it is difficult to recycle plastics efficiently.
In the next article, we’ll look into how plastics have transformed our world, making our daily life more affordable, safer, cleaner, and more fun.