Eugene is a qualified control/instrumentation engineer Bsc (Eng) and has worked as a developer of electronics & software for SCADA systems.
What Are Plastics?
"Plastic" is a term applied to any material which can be molded or bent into shape. So for instance soft toffee, modeling clay or red hot iron is plastic because it can be reshaped. In general, though when we speak of plastic, we mean polymers or synthetic materials made from petrochemicals.
There are at least 10 different types of plastics used in the home, the type used depending on the application. Many of these plastics can be recycled and are marked with a symbol and numeric code indicating the plastic type.
Types of Plastic Used Around the Home
There are lots of different types of plastics used in and about the home. The most common ones are:
- Polyethylene (Polythene)
- Poly Vinyl Chloride (PVC) also known as vinyl
- Polytetrafluoroethylene (Teflon)
- Polyesters, polyethylene terephthalate (PET) being the most common
Note: These numbers are not the plastic ID codes. See the information about each plastic below for codes.
What Is Plastic Used For?
Well virtually everything! From the sixties onwards, plastic began to replace or supplement many items which were traditionally made from materials such as metal, wood, glass, stone, ceramic and natural textiles. Some examples:
- Textiles: Cotton, wool, silk, linen and hemp were the original textiles used from ancient times. We now have acrylic, polyester and nylon
- Footwear: Shoes originally had leather uppers and soles. PVC is now used for sneakers, and soles are made from PVC or polyurethane foam
- Windows and doors: Originally made from timber, they are now also made from PVC
- Food storage, eating and drinking utensils and bottles: They were originally ceramic, glass or metal but are now also made from polyester, polypropylene and polyethylene (Polythene)
- Electrical insulation: Originally rubber, now also PVC
- Furniture: Plastics such as polystyrene are used for stackable, hard seating. Padded seating coverings are often made from PVC or "vinyl" and soft, flexible, polyurethane foam forms the internal padding
- Car and machine parts: Many parts in cars were made from metals such as steel, brass, aluminum alloy and rubber. These are now often replaced by plastics such as PVC, nylon, ABS and polystyrene
- Casings of electronic/electrical devices and appliances: Originally made from wood, metal or Bakelite, they are now generally made from polystyrene, polypropylene or ABS
- Fixtures and fittings in homes: Lighting, electrical fittings and conduit and bathroom fittings
- Plumbing: PVC, PEX (cross-linked high-density polyethylene), polybutylene and CPVC are extensively used for domestic plumbing, drainage pipes, water distribution mains to homes, gas distribution and protective conduit for underground electrical cables.
Why Is Plastic Used So Much?
- It's cheap and made from a relatively inexpensive raw material.
- It's relatively strong and can be used for many applications.
- Many plastics are inert so can be used in contact with solvents, acids and alkalis, water and other chemicals without suffering any ill effects.
- Unlike organic materials such as wood and natural textiles, plastic doesn't decay when exposed to wet or damp conditions for long periods.
- Thermoplastics can be molded into lots of different shapes using an industrial process called injection molding (basically forcing soft plastic into a mold under high pressure). So no machining is necessary as is the case with metals. Plastics can also easily be 3D printed.
- Plastics can be easily colored.
- Nylon, a tough and durable type of plastic can be used for moving parts in machinery without the requirement of lubrication (it has a relatively low coefficient of friction like Teflon).
- Plastic is a non conductor of electricity, so it can be used as an insulator in electrical appliances.
- Many plastics can be easily recycled by being melted down or shredded to make new products.
- As a synthetic fiber, it can be more durable than natural fibers when made into textiles.
- Many plastics are good thermal insulators, so they are used as handles on kitchen utensils, tools, saucepan lids etc.
What Are the Disadvantages of Plastic?
- Unlike scrap metals for instance which are more valuable, it is such a ubiquitous and cheap material that there has been very little incentive to recycle it until recent decades. So it ends up in landfils and as litter.
- For some applications, plastics cannot be used because they lack the strength of metals. Composite materials such as carbon fiber (a fiber reinforced polymer) will eventually become more widely used.
- While plastic parts are often used in machines and tools, they aren't as tough or durable as metal, so plastic parts can wear or break more easily.
- Ultra Violet (UV) exposure from sunlight can cause plastics to crack and degrade over time unless special additives are added to the material during manufacture.
- There are concerns about carcinogens used as fillers or trapped monomers leaching out of plastics used in food storage containers and drinking vessels.
- It can't be used for applications where it is exposed to very high temperatures.
- Microbeads less than 1mm diameter used in personal care products as an abrasive, pose an environmental hazard and may harm aquatic animals.
What Are the Two Main Categories of Plastics?
Plastics can be broadly divided into thermoplastic and thermosetting types.
Thermosets are heated during manufacture and a non-reversible chemical reaction takes place. Once they have cooled and set, they stay solid and can't be re-heated and re-molded. Examples are Bakelite, urea formaldehyde and vulcanization of rubber.
Thermoplastics can be reheated repeatedly without undergoing any chemical change. This allows them to be reshaped or recycled into new materials. Examples are PVC, polyethylene and polypropylene.
What is Plastic Made Of?
There are several stages in the manufacture of plastic, but it all starts with crude oil and natural gas. There are three main stages:
- Stage 1 - Crude oil (petroleum) and natural gas is extracted from ground
- Stage 2 - Intermediate products known as petrochemicals are made from crude oil and natural gas.
- Stage 3 - Polymerization and other chemical processes are used to produce plastics from petrochemicals
Stage 1 - Crude Oil and Natural Gas, the Raw Materials For Plastic
The raw material for most plastics is crude oil, also known as petroleum. This is a thick black, brown, yellowish or greenish liquid, extracted from the ground using oil wells on land or at sea. Crude oil was formed when creatures and plants such as zooplankton and algae died and settled to the bottom of the ocean. Over millions of years, sand, shells and other stuff collected on top of them. As a result of heat and pressure, this organic material was transformed into oil.
Crude oil is a complex mix or soup of lots of chemicals and must be refined. Oil refineries are large industrial complexes which process thousands of barrels of oil daily. In a refinery the oil is cleaned of contaminates such as salt water. Several processes are then used to break the oil up into its constituent components, typical of which is fractional distillation. In this process, oil is heated and various compounds boil off at different temperatures and can be separated. This results in distillates such as gasoline, kerosene, lubricating oil, wax and asphalt (bitumen). Petrochemicals such as benzene, toulene and xylene or BTX are also produced here.
Natural gas is also used as a raw material. This is processed at a natural gas processing plant into a variety of different types of gases.
Stage 2 - Petrochemicals are the Intermediate Product
Petrochemicals are the intermediate chemicals in the production of plastics. Typical petrochemicals are ethylene, propylene, benzene, butadeine, toulene and xylene. Petrochemicals are produced in petroleum refineries, natural gas processing plants and by a process known as cracking.
Stage 3 - Polymerization
In this process, the petrochemical monomer raw product is converted into a long chain polymer or plastic. A typical petrochemical is ethylene gas with the formula C2H4. In the polymerization process, an activator known as a catalyst speeds up the chemical reaction. Lots of ethylene molecules join together into chains to form a polymer.
How to Identify Plastic Type
Most plastic products or their component parts are marked with a plastic identification code symbol specifying the type, allowing ease of identification for recycling purposes.
There are many polyesters but the commonest type encountered in the home is PETE or Polyethylene terephthalate. PETE is spun into a synthetic fiber which is used to produce textiles. Polyester fiber is also mixed with natural fibers such as cotton to improve durability.
- Shirts, trousers, coats and other clothing, sometimes under the brand name "Terylene"
- Bed sheets
- Plastic bottles
- Insulating tapes
- Insulation in clothing and as padding in duvets, pillows etc
Products Made From PET
High density polyethylene has a high strength to weight ratio and also a high resistance to solvents, acids and other chemicals.
- Plastic bags
- Storage containers for food and other products
- Beverage bottles
- Toiletry bottles
- Fuel tanks on vehicles and garden/yard power equipment
- Containers for household cleaning chemicals
- Gasoline storage containers
- Storage containers for motor oil
- Blow molded cases for tools
Products Made From HDPE
Poly Vinyl Chloride (PVC)
Poly Vinyl Chloride is more commonly known by the abbreviation PVC or "vinyl". It comes in two forms rigid or flexible. The rigid form is used for structural work e.g door and window frames and the frame members of plastic greenhouses. The flexible form is widely used as electrical insulation, upholstery coverings and inflatable products.
- Doors, windows and greenhouse frames
- Upholstery covering, chair seat coverings
- Beach balls, footballs and other inflatable products
- Fascia and soffit
- Downpipes and gutters
- Waste and water pipe
- Insulation for electrical wire
- Electrical conduit
- "Vinyl" records
Products Made From PVC
Low Density Polyethylene (LDPE)
Low Density Polyethylene is a soft flexible plastic widely used for making clear plastic bags and sheeting. It has a higher resilience than HDPE, which basically means that it can be stretched or deformed more without cracking or ripping. You can tell the difference between an LDPE and HDPE bag by scrunching them up. HDPE bags make lots of crackly noise. It is ideal also for snap on lids as it can deform and seal around the rim of the container.
- Plastic bags
- Clear flexible plastic sheeting, e.g. for polytunnels
- Soft flexible snap on lids
- Shrink wrap (cling film)
- Waterproof linings of cardboard juice and milk cartons
Products Made From LDPE
Polypropylene is a tough, flexible plastic and used for applications which require these properties. It also resistant to fatigue which means that it can be repeatedly deformed or strained without cracking. PP also has good resistance to acids and solvents. Polypropylene is able to withstand higher temperatures than HDPE and so is used for applications where a product must be sterilized or heated, e,g. kettles and dishwasher proof kitchenware. It is also used for containers which contain dairy products such as butter, as it can withstand the heat given off by products during industrial filling processes.
A disadvantage of PP is that it degrades when exposed to heat and UV present in sunlight, so additives must be used if products are required to be long lasting in sunshine
- Beverage bottles
- Dish washer proof plates and food storage containers
- Living hinges on lids
- Food storage containers
- Dairy product containers
- Toiletry bottles
- Coal sacks
- Ratchet straps (tie down straps for holding loads during transport)
Products Made From Polypropylene
Polystyrene has two main advantages. It is a stiff and rigid polymer, and unlike other plastics which are translucent or opaque, polystyrene can be made clear. So it is ideal for applications which require these characteristics such as CD and display cases.
- CD cases and display boxes
- Casings for kitchen appliances, TVs and Radios, torches and other electrical gadgets
- Seed trays
- Blister packing
- Disposable cutlery
- Disposable ballpoint pens
- Expanded polystyrene (Styrofoam) is used as insulation, as a packing material and for disposable cups
Products Made From Polystyrene
Other Plastics Used in the Home
Several polymers which don't have their own specific recycling number are classed under category 7 as "other plastics". Not all of these are recyclable
Other plastics used in the home are:
- Nylon - Tough and durable and used for ladies tights, sports clothing and moving parts in machines
- Polycarbonate - This is tough and durable and can be bent and deformed to a large extent without cracking. It is used for making sunglasses, safety glasses, CDs and as synthetic "glass" in greenhouses
- Acrylonitrile butadiene styrene (ABS) - Another tough plastic with high impact resistance. It is used for making Lego bricks, carrying cases, electrical boxes and computer monitor and printer cases.
- Urea formaldehyde - Commonly used for sockets, plugs, switches and other electrical fittings
- Polyurethane - Used in foam form as a padding in cushions and upholstery, air filters on lawn mower engines and as packing. Some air and fuel lines are made from this material. Hard foam soles on footwear are also polyurethane based
- Polytetrafluoroethylene (PTFE) - This plastic has a very low friction coefficient, i.e., it is "slippy". It is known by the brand name Teflon as the non-stick coating on cooking utensils. It is also used in tape form for sealing the threads on plumbing joints
- Polymethyl methacrylate (PMMA) or Acrylic - Used as a synthetic fiber in sweaters and as clear sheeting or pipe under the trade names "Perspex", "Plexiglas", "Acrylite" and "Lucite".
- Nitrile rubber - one of the many types of synthetic rubbers. These are used for a variety of products including gloves, o-rings, sealants, fuel lines and water hoses in vehicles, wellingtons and anything which requires a flexible, waterproof material
Older plastics used in the home were:
- Bakelite This is a thermosetting plastic, used in the past for electrical fittings, electrical insulation, door knobs and saucepan handles. Because it is a thermoset, it doesn't melt or deform when subjected to high temperatures.
- Celluloid Used for making dolls, musical instruments, pens, table tennis balls, cutlery handles and as a veneer for clocks and furniture
Other Plastics Used in the Home
Not all plastics are recyclable, but it depends on region and country. Soft plastic such as plastic bags and film made from low and high density polyethylene, expanded polystyrene packing and hard polystyrene casings are generally not accepted by waste collection service providers. Expanded polystyrene needs to be compacted and the cost of building large compactors is high.
PET, HDPE and PP as used in bottles, lids, food trays and containers are generally recyclable
Plastics in the Ocean — What are Microplastics?
Tiny microbeads less than 1mm diameter made from polyethylene, polypropylene and polystyrene are used as an abrasive ingredient in personal care products such as skin exfoliating creams and toothpaste. These materials end up in waste water and pass through sewage treatment plants unhindered, and then get carried via rivers to our oceans. These pose an environmental hazard and may harm aquatic animals. Plastic items in our home and from land based industry and fishing activity also degrade over time and the tiny fragments eventually end up in the ocean. Larger items such as plastic bottles, floats from fishing nets, items lost or disposed of overboard from ships also pollute the seas.
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This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
Questions & Answers
Question: Is there any health hazard when the plastic of a portable electric heater smells when heated?
Answer: It depends. It could be just a "new" smell when any solvents from the plastic or residue from manufacturing on the element evaporates. If this is a new phenomenon, it could be due to loose connections causing arcing and overheating. The danger of fire would be more of a worry than a hazard from the plastic smell, so it would be wise to have it checked out.
Question: What kind of plastic are chairs made from if they have a metal frame and are used outside?
Answer: It's quite possible they're made from PVC or alternatively ABS. Another alternative is polypropylene, which is a hard wearing, durable plastic.
Question: Are my rubber boots made of PVC, polyethylene or polypropylene?
Answer: They could be made of vulcanized natural rubber, but they are most likely made of synthetic rubber or PVC. PVC or "vinyl" has a distinctive smell.
Question: What is the type of plastic used in housing on a leaf blower?
Answer: Probably polystyrene, although ABS is sometimes used.
Question: What kind of plastic is used for melamine items; melamine trays to be precise?
Answer: Melamine is a thermosetting resin compound with the formula C3H6N6. It's used in the manufacture of trays and similar items and also as a surface layer for tables and worktops under the brand name "Formica."
Question: What kind of plastic is used in small domestic appliances?
Answer: Possibly polystyrene or ABS for the case. Other plastics could be used internally, such as nylon for gears and moving parts, phenolic resin or glass reinforced epoxy resin for PCBs and polycarbonate for clear screens.
© 2014 Eugene Brennan
Eugene Brennan (author) from Ireland on August 09, 2020:
It's quite possibly ABS (acrylonitrile butadiene styrene) which is used for making lots of consumer products such as appliance cases and toys (e.g. Lego bricks). You can glue it with "super glue" or epoxy resin.
Betsy Bayha on August 09, 2020:
Hi There--Thanks for your article.
I have a home office printer that works perfectly fine, but a small piece of plastic broke off the tray that holds the paper straight. I don't want to throw out the printer for such a small repair. Is there a plastic glue that works to repair this type of thing? I don't see the triangular plastic symbol on my printer, so I'm not sure what type of plastic it is.
Thanks for any advice you can provide.
Jack Smith on June 01, 2020:
I was very impressed with your article.
I just assumed that your research must have included more applications (other than the examples listed in your article) for each type of plastic, that may have includded cutting boards.
Or simply, i assumed that by extrapolating known characteristics of each plastic that you could have arrived at a suitable/meaningful responce for my intended topics.(cutting boards and knife handles)
If you dont know, Im afraid no one will. Secondly, i am also surprised that you did not at least consult with a plastic technolagist before composing your article.
I am already sure of the best materials to use and merely hoped that, you, as an authority, would have confirmed my findings, before I plan to make a rather expensive purchase.
I would, of course, welcome any plastics technologjst that you may come across to offer an opposing viewpoint.. Thanks for your reply.
Eugene Brennan (author) from Ireland on June 01, 2020:
I don't know the answers to your questions Jack. I'm not a plastics technologist. Maybe other readers will have suggestions.
Jack Smith on May 31, 2020:
Which plastic would be considdered best to use in the constuction of a food cutting board.
One would have to consider, (in order of impotance) 1. Health concerns, ie., contamination of food while being sliced on the board. I believe two standards must be met, NSF Approved, Natioal Sanitary Foundation and BPA Free. 2. Knife blade preservation, ie.,you would not want your expensive forged cuttlery/knife blades to be dulled/damaged while slicing and 3. (Least important)Board Preservation ie.,which material would hold up, be the best for this use.
Follow up Questions: A.Could the chozen material come in colors? B.what would be the reccomended board thickness, ie. 1/2 inch thick? (For the boards structural integrity)
C.Do you think there would be a problem with making this board reversible?
My findings indicate the best solution is a 1/2 inch thick HDPE, a High Density Polyethylene Board
* Do you agree? One would be amazed at the marketplace offerings where apparently the makers of boards use Polypropylene interchangeably with Polyethylene and are themselves, either nasty, ill informed or don't care.
* If you agree with HDPE, why is this NOT widely available for purchase?
* If you know where to purchase it in N.Y., could you let me know?
* If HDPE is the solution, my next request is to ask what type of plastic would make a good "Rubberized" Mat, that could be used under the board(even under a wood board, for the same reason) to prevent sliding/movement of the cutting board, while providing some shock absorbing qualties.
Lastly, what type of plastic is Polyoxymethylene(POM). Is it really the best for Cutlery, being non porous, not absorbing bacteria and long lastling.
Eugene Brennan (author) from Ireland on April 23, 2020:
I'm not an expert on the materials used for this application, however I would think nylon is probably the most durable material. It's used in machines for gears which are subject to wear as the teeth mesh possibly hundreds of times per second. UV resistance and degradation would be another consideration. Is nylon available with an additive included to give it resistance to UV? Doors and windows made from uPVC are UV resistance because they have to last for decades. HDPE is used for bottles that hold household bleach and for fuel tanks so it's chemical and solvent resistant.
Esther on April 22, 2020:
Hi, I wonder if you could help, I am looking into using synthetic roof thatch in Indonesia but manufacturers use different plastics, some use HDPE others pvc and recently I found nylon. Taking into consideration hi climate temperatures, and possibilities of UV fading and long term resistance , which plastic type would be more suitable for outdoor constant use ?
Indu mathi on March 20, 2020:
There is more information.it is easy to read it and the informations are so crisp and clear.there are also pictures related to the topic.go forward and all the best for the information you give for other topics
.I have a doubt why Teflon is used for making non stick cooking pans and other cookwares
Ashis Basu, from Kolkata India on January 11, 2020:
Daily, milk is delivered to homes in single use plastic bags. After use, these are discarded. The bags go out to sea and ultimately land up inside whales and other big fish .
Can these used plastic bags be converted to make home furniture (door & window frames, chairs and tables etc)? Also, by using used plastics, de-forestation is prevented, enabling regeneration of forests and associated other benefits.
What would be the way to go forward?
Eugene Brennan (author) from Ireland on December 03, 2019:
Possibly polyester or polypropylene. It will need to be a durable material to stand up to wear. Usually the material is indicated on the washing label.
Regina on December 02, 2019:
What plastic is ised for mattress covers
Jess on June 04, 2019:
What type of plastics is used for manufacturing computer hardware
Eugene Brennan (author) from Ireland on March 09, 2019:
Usually it's made from a thermosetting resin that doesn't soften when it gets hot. This would originally have been Bakelite, but probably urea formaldehyde is used now.
Elita So on March 08, 2019:
what type of plastic is the typical kettle handle made out of?
Dermot on January 14, 2019:
Nicely done, well written and useful photos to accompany the text
Jev on February 10, 2018:
Thank you so much and more power to you. Your info is so great that makes understanding of the plastics easier and makes me feel happy knowing everything you share here in your info.
Have a good day always.
Ravi Melwani on October 07, 2017:
Hi Eugene Brennan, I am from India and want to thank you profusely for putting this much of valuable info required by a layman in his daily life. If you had not put this info together, I would have had to visit numerous websites and go through don't know how many books plus spending time and effort required.
My sincerest appreciation of the efforts you have put in. Looking forward to more articles from you.
with best regards,
Linda on July 20, 2016:
Wow, what a ton of info! Been researching types of plastics so I can do some welding repairs at home. Your article is TMI for me, but it answers a lot of questions that I hadn't found elsewhere. Like what kinds of things are made from what types of plastic. You even included Bakelite. Thanks a bunch!