When you think about plastic, you might imagine water bottles or packaging materials, but plastic is much more than that. Let’s take a closer look at what plastics are made of and some of their essential properties.
Plastics are mostly synthetic materials made from polymers – long molecules built around chains of carbon atoms, with hydrogen, oxygen, sulfur, and nitrogen filling in the spaces. These chains can have thousands of atoms, which is one reason why plastics are so strong and durable.
Plastics exhibit a property called plasticity, allowing them to be molded or shaped into various forms. This, combined with other properties like low density, low electrical conductivity, and transparency, makes plastic a versatile material. You can use plastic in various everyday items, such as car parts, toys, and even medical equipment.
There are three main groups of plastic:
- 1. Thermoplastics
- 2. Thermosetting polymers
- 3. Elastomers
Thermoplastics are plastics that soften when heated and harden when cooled, making them easy to mold and shape. Some examples include polyethylene, polypropylene, and PVC.
Thermosetting polymers harden permanently when heated, and they cannot be reshaped or remolded once set. These types of plastics include phenolic resins, melamine, and urea-formaldehyde.
Elastomers are rubber-like materials that can be stretched and deformed but still return to their original shape. Examples include natural rubber, polyurethane, and silicone.
The Production of Plastic
Plastic is primarily made from fossil fuels such as cellulose, crude oil, natural gas, and coal. These raw materials are the sources of hydrocarbons, which are organic molecules consisting of carbon and hydrogen atoms. To transform these raw materials into plastic, they first need to be refined into ethane and propane, respectively.
The refinement process typically happens in refineries where fossil fuels are converted into various petroleum products. Ethane and propane are further treated with heat in a process called cracking. Cracking breaks down the complex hydrocarbons into simpler molecules, converting ethane into ethylene and propane into propylene. These materials are then combined to create different types of polymers, which form various kinds of plastics.
There are two main types of cracking: steam cracking and catalytic cracking. In steam cracking, the chemicals are mixed with steam and heated to high temperatures, while in catalytic cracking, a catalyst is used to lower the required temperature and pressure. Once the cracked hydrocarbons are separated using fractionation equipment, ethylene and propylene are formed into monomers. Finally, the polymerization of these monomers results in the production of various plastics.
Different Types of Plastics and Their Chemical Components
Plastics are made from organic polymers, with most industrial plastics originating from petrochemicals. These polymers are formed from chains of carbon atoms, often with attachments of oxygen, nitrogen, or sulfur atoms. Monomers serve as the building blocks of these polymers, with each polymer chain comprising several thousand repeating monomer units.
Here is a quick introduction to common plastic and their components:
|Polymerization of ethylene, which includes HDPE (high-density polyethylene) and LDPE (low-density polyethylene)
|Plastic bags, containers
|Polymerization of propylene
|Packaging, textiles, automotive parts
|Polyethylene Terephthalate (PET)
|Polymerization of ethylene glycol and terephthalic acid
|Strong, lightweight, clear
|Beverage bottles, food packaging
|Polyvinyl Chloride (PVC)
|Polymerization of vinyl chloride monomers
|Durable, rigid, chemical resistance
|Pipes, cables, flooring
|Polymerization of styrene
|Insulating, rigid foam
|Foam cups, packaging materials
|Condensation of amine and carboxylic acid
|Strong, abrasion resistant
|Fibers, automotive parts
|Polylactic Acid (PLA)
|Polymerization of lactic acid from corn starch, etc.
|Compostable food containers
|Polymerization of ester monomers
|Reaction of polyol and isocyanate
|Cushioning foams, coatings
|Acrylonitrile Butadiene Styrene (ABS)
|Polymerization of styrene and acrylonitrile
|Electronic housings, automotive parts
|Polymerization of tetrafluoroethylene
|Chemically inert, non-stick
|Non-stick cookware (Teflon)
Trend Of The Plastic: Bioplastics
You might be curious about bioplastics, a more eco-friendly alternative to conventional plastics. These plastics are derived from renewable biomass sources, such as vegetable fats, oils, corn starch, and recycled food waste. They offer several benefits, particularly in terms of sustainability and environmental impact.
One of the key advantages of bioplastics is that they are biodegradable. This means that they can be broken down by microorganisms such as bacteria, ultimately turning into organic matter. Unlike traditional plastics, which persist in the environment for long periods and contribute to pollution, biodegradable bioplastics offer a more sustainable solution.
Now, bioplastics are a diverse group, and they can be made from several different materials. Some common options include:
- Polylactic Acid (PLA): This bioplastic is derived from fermented plant sugars, usually from corn or sugarcane. It’s widely used for food packaging and disposable cutlery.
- Polyhydroxyalkanoates (PHA): These are produced by bacteria that consume organic materials like vegetable oils or food waste. They’re suitable for a range of applications, including agricultural films and packaging.
- Starch-based bioplastics: As the name suggests, these are made from starch, which is a natural polymer. They’re often used in disposable items like plates and cups.
Frequently Asked Questions
What are common types of plastic?
There are several common types of plastic that you might encounter in your daily life. Some of the most widely used include Polyethylene (PE), Polypropylene (PP), Polyvinyl Chloride (PVC), and Polyethylene Terephthalate (PET). Each type of plastic has its own properties and applications, from packaging materials to automotive parts and electronics.
What natural resources are used to make plastic?
Plastic is primarily made from fossil fuels, such as crude oil, natural gas, and coal. These resources are processed through a technique called cracking, which converts them into hydrocarbon monomers. These monomers are then combined to create a variety of plastic polymers with unique properties and characteristics.
How do plant-based plastics differ from traditional ones?
Plant-based plastics, also known as bioplastics, are made from renewable resources like corn, sugarcane, or potato starch. They differ from traditional plastics in that they can be designed to biodegrade more quickly and have a smaller environmental impact. However, it’s important to note that not all bioplastics are compostable or eco-friendly, so it’s essential to understand their specific properties and disposal requirements.