Facts About Plastics that You Should Know
The word plastic is derived from the Greek word Plastikos, meaning to mold or form. Plastic was first developed as a replacement for ivory in the 1860s. Since then plastic has become an essential part of all manufacturing industries.
Manufacturing industries use plastic in many areas of application because it is easy to bend and mold into different shapes.
Plastics are made from petrochemicals that are derived from fossil fuels such coal, crude oil and natural gas.
What are plastics?
Plastics are made of long chains of polymers. Polymers are made of single units of repeating monomers. The monomers are combined in different ways to produce different types of plastics.
In order to get a clear picture about plastics, it is important to understand the following terms -
Monomer - Monomer is the basic unit of a chemical substance that can be combined in different ways to form a more complex substance. The term mono means one.
Polymers - Polymers are long chains of monomers connected in different ways to form a complex substance. Poly means many.
Hydrocarbons - Hydrocarbons are organic compounds that can be found in crude oil and natural gas. They are made only of carbon and hydrogen atoms.
What is plastic?
Plastic is a material that is made of long chains of polymers. (Polymers are repeating units of monomers.) During the manufacture of plastics, monomers are combined in different ways to produce different types of plastics.
Polymers in plastics are made of long chains of hydrocarbon molecules. The carbon atoms present in the hydrocarbon molecules join to form the framework of the hydrocarbon molecule, and the hydrogen atoms act as links to other carbon atoms forming a continuous chain.
The chain of hydrocarbon molecules can be a single straight chain or branch off in different directions to form a more complex chain.
Polyethylene is an example of thermoplastic that is used in most industrial and commercial applications. Thermoplastic is a type of plastic that can be melted into a liquid and remolded as it cools down to become a solid.
The diagram below is an example of a polyethylene plastic -
Thermoplastics are polymers that can be melted and recast into different shapes. They can be melted and recast several times without losing much of their original properties
Examples of Thermoplastics
Acrylonitrile Butadiene Styrene (ABS) is a thermoplastic that is used to manufacture sports equipment, Lego Blocks, and automobile parts.
Polycarbonate is a type of thermoplastic used to make Compact Discs, beverage bottles, food storage containers, eyeglass lenses, etc.
Polyethylene is another thermoplastic that is used to make shampoo bottles, plastic grocery bags, and bullet proof vests. Thermoplastics can be recycled and reused.
Thermosets are also known as thermosetting plastics. Thye are synthetic materials that can form a three-dimensional network when chemically treated.
The first thermoset plastic called Bakelite was developed by Dr. Leo Baekeland in 1909. The advantage with thermoset plastics is that they retain their shape and properties at high temperatures.
The ability to retain the shape and original properties even at high temperatures make thermosets ideal to make things that are solid and durable.
Thermosets are used in the manufacture of electronic chips, fiber-reinforced composites, polymeric coatings. Thermosets cannot be recycled, remolded or reshaped.
Polyvinyl Chloride (PVC)
Commercial use of PVC was first started by Waldo Semon in the 1920s while trying to create a synthetic replacement for natural rubber.
PVC plastics are thermoplastics that are made of 57% chlorine and 43% carbon. The production of PVCs is less dependent on fossil fuels because the chlorine used to make PVC is derived from industrial grade salt and the carbon is derived from oil or gas.
PVC plastics are durable, light, strong, fire resistant with low permeability and high insulation properties. PVCs are used in the manufacture of building materials such as window and door frames, floor and wall coverings, roofing sheets, tunnel linings, swimming pools and reservoirs.
PVC is also used for the following -
- Pipings for water and sewerage transport and fittings and ducts for power and telecommunications.
- Coatings for tarpaulins, rainwear and corrugated metal sheets.
- Insulation and sheathing for low voltage power supplies, telecommunications, appliances and automotive applications.
- Packaging for pharmaceuticals, food and confectionery, water and fruit juices, labels and presentation trays.
- Manufacture of medical products such as blood bags, transfusion tubes and surgical gloves.
- Manufacture of garden hoses, footwear, inflatable pools and tents.
Commercial use of PVC first started by Waldo Semon in the 1920s while trying to create a synthetic replacement for natural rubber.
PVC plastics are thermoplastics that are made of 57 % chlorine and 43% carbon. The production of PVCs is less dependent on fossil fuels because the chlorine used to make PVC is derived from industrial grade salt and the carbon is derived from oil or gas.
Polyurethane was discovered in 1930 by Professor Dr.Otto Bayer. Polyurethane is a durable, flexible and a resilient material that is manufactured from petrochemicals. Dr.Otto Bayer is known as the Father of the polyurethane industry.
Polyurethane is manufactured by combining two monomers – diisocyanate and diol or polyol through a chemical reaction. Polyurethane can be in the form of a liquid, foam or solid depending upon the monomers that are used to produce polyurethane.
Polyurethane is highly flexible, resistant to abrasion and high impact, can withstand wear and tear, resistant to water, oil and grease. It is highly resilient and is a good conductor of electricity. Polyurethane bonds well with plastics, metals and wood.
Even though polyurethane is made from fossil fuel, it helps to preserve the natural resources of the planet in the following ways -
- Coating a product with polyurethane extends the life of the product thereby reducing the need to produce new products frequently
- Polyurethane helps to insulate buildings. Insulation with polyurethane helps to decrease the consumption of gas, oil and electricity
- Polyurethane foams used tin refrigerators help to preserve food for a longer time
Polyurethane can be recycled chemically by breaking them down into monomers and making new polyurethane or mechanically by using the polyurethane in its polymer form. It also helps to recycle other materials such as rubber and wood.
Polyurethane is made of petrochemicals and they should be recycled to save valuable resources and energy.
PET is a short form for Polyethylene terephthalate. PET plastics were first synthesized by Dupont Chemists while they were conducting a research to make new textile fibers, but the actual technology for the manufacture of these textiles was developed by Imperial Chemical Industries.
PET plastics are durable, can withstand high pressure and do not burst open when falling. It has very good barrier properties and helps to preserve the fizz in aerated drinks. PET products can be recycled and reused.
PET plastics are used in the manufacture of the following -
- Bottles for beverages such as soft drinks, fruit juices, mineral waters, carbonated drinks
- Bottles for cooking and salad oils, sauces, and dressings
- Wide mouthed jars and tubs for jam, preserves, fruits and dried foods
- Trays for pre-cooked meals that can be reheated and other PET products
PET products are made from crude oil derivatives and must be recycled to save earth's resources.
Bioplastics can be bio-based, biodegradable or both. The term bioplastic refers to plastics that meet one or both of the following two conditions-
- Bioplastics must be partially derived from renewable (plant-based) resources
- Bioplastics can be degraded into water and carbon dioxide by naturally occurring microorganisms present in the environment. During this process, a little biomass is created
Conventional plastics do not meet any of the conditions mentioned above.
Examples of Bioplastics
Polylactic acid (PLA), PolyCaproLactance (PLC), polyesteramide, PolyHydroxyButyrate-covalerate (PHBV) made from plants such as canola, soybean, corn, and potatoes. Bioplastics can also be made from wastes of the food industry.
The use of renewable resources to produce plastic helps to save fossil fuel and reduces the emission of the greenhouse gas carbon dioxide.
Bioplastics can be classified into two different types of plastics - bio-based plastics and biodegradable plastics.
Bio-based products are manufactured partly from biomass. The very first bio-based plastic was Polyhydroxybutyrate (PBH), was discovered in 1926 by Maurice Lemoigne, a French researcher.
Maurice Lemoigne discovered bio-based plastic while working with the bacterium Bacillus megaterium. At first his discovery was not acknowledged by the world but with the recent fossil fuel crisis bio-based plastics have become an important topic for further research.
Bio-based plastics are extensively used in packaging industries.
Examples of biomass
Dead trees branches and leaves, tree stumps, branches and leaves from yard clippings, wood chips. Industrial biomass is obtained from plants such as Miscanthus, Switch Grass, Hemp, Corn, Sugarcane, Bamboo and trees such as Eucalyptus and Palm.
Biodegradable plastics are environment-friendly plastics that can be broken down by microbes such as bacteria and fungi present in the environment.
According to the Biodegradable Plastic Institute, a biodegradable material is a material that breaks down under the right conditions by the microbes in the environment and use the broken down materials as a food source.
Biodegradable plastics are not necessarily biobased
Plastics made from fossil fuels alone can be made biodegradable by adding chemical additives during the process of manufacturing the plastics thereby making the plastic biodegradable and eco-friendly.
A biodegradable product can have non-biodegradable ingredients that do not decompose naturally or have materials that can be recycled by curbside recycling programs.
Biodegradable plastics should not be thrown out into the environment because they take a long time to decompose in landfills due to lack of oxygen, humidity, and low temperatures.
Biodegradable plastics should be recycled through curbside recycle programs. Recycling programs take the collected biodegradable plastics to huge composting facilities where they decompose in a short time under controlled environments.
Biodegradable plastics are used for
- Food packaging – packaging that can be composted along with its contents when it has passed the expiry date
- Production of agricultural plastic sheeting that can be plowed into biodegradable mulch and seed films
- Medical- absorbable sutures, micro-devices containing medicine which break down inside the body
- Disposable plates, spoons, cups, forks
Cellophane is a 100% biodegradable material made from plants and tree cellulose. The very first time, cellophane was made by the French scientist in 1920.
Plastics and the Environment
Plastics have become a part of our everyday life. We use many items made of different types of plastics without fully realizing the impact they have on the environment.
Even though plastics have many uses they have become a threat to the environment. The best solution would be to cut down on the use of plastics. Instead of recycling them it is better to avoid the use of plastic items or reuse the ones that we already have.
© 2015 Nithya Venkat