Get to Know the 7 Types of Plastic- Plastics 101

Plastics are more broadly categorized by their monomers. Here are the 7 types of plastics we see on the daily. These plastics are identified by “resin identification codes”, the numbers inside the triangles, meant to make recycling much easier. In this article, we have ordered the list of plastics according to their respective resin identification codes.

  1. Polyethylene Terephthalate (PET or PETE or Polyester)

AKA beverage bottle plastics. PET suits the job of keeping beverages shielded from bacteria inexpensively while keeping its glossy looks. Polyethylene Terephthalate is a lightweight plastic known for its excellent moisture barrier properties and resistance to alcohols, oils, and diluted acids. The common myth of leaving bottles in a hot car proves to be true, as PET contains the compound antimony trioxide, a carcinogen. Hotter temperatures stimulate the increase in the release of antimony trioxide to the contained liquid. This wrinkle free plastic is non biodegradable, due to its inert nature.

PET is usually manufactured using blow moulding, injection moulding, 3D printing and extrusion. Blow moulding is by far a favourite among manufacturers. Blow moulding is a clean manufacturing technique where granular plastic pellets are melted to be captured by moulds, followed by a blast of hot air which causes the plastic to take up the shape of the mould.

2.High Density Polyethylene (HDPE)

World’s most loved plastic. HDPE is the most widely used type of plastic due to its unbranched polymer chains, which makes it super dense and thick, but mouldable at the same time. Aside from that, it is malleable, long lasting, impact resistant, lightweight and mould resistant and is easily recyclable! What is there not to like?

Although its safety has been universally accepted, HDPE has been linked to contain oestrogen mimicking compounds that are stimulated to release when exposed under UV light. It is linked to hormonal imbalance issues.

3. Polyvinyl Chloride (PVC)

Alias the killer. Found in toys, wraps, packaging, blood bags and water pipes, PVC is utilized in almost every industry. Water pipes in municipalities are often made out of Polyvinyl Chloride, because it is easy to install and odourless. Its base materials are: Chloride salts and Petroleum based ethylene. Chlorides are extracted from the seawater through electrolysis and ethylene is harvested through the cracking of petroleum.

57% of PVC is pure chloride, releasing chemicals like bisphenol A (BPA), lead, cadmium, dioxins and mercury. It has been proven that PVC causes fetal development issues, hormonal imbalance, cancer and diminished lung function. It is advised that the general public use PVC only when necessary.

4. Low Density Polyethylene (LDPE)

Wrinkly supermarket bag plastics. LDPE plastics are polyethylenes, polymers with simple and branched structures (4000–40 000 carbon atoms/polymer), making them less dense and crystalline in form. It is highly flexible and cheap to produce. It has good resistance towards acids, alcohols, esters, and bases making it a suitable material for food and hardware applications. This type of plastic is deemed safe.

LDPE manufacturing employs a radical polymerization process, where an excess of 99.9% pure ethene is compressed and passed into a reactor and initiator with oxygen or natural peroxides. The polyethene is then extruded and cut into fine granules ready for the blow moulding process.

5. Polypropylene (PP)

Polypropylene(C3H6)n, a hydrocarbon and a monomer of propene also known as PP, is a rigid thermoplastic addition polymer. Polypropylene is also known to be more resistant to heat and degradation from UV rays than any other plastics. Polypropylene is widely used in the automotive industry(car bumpers or the carpet fibres of the interior) and consumer goods(water bottles or food containers).

Same as LDPE, PP is safe for food and drink use because it does not transmit chemicals into the things humans consume due to its relatively high melting point(171°C). It is also recyclable giving every reason why it’s better to use this.

6. Polystyrene (PS)

The foamy one. 95% of polystyrene is composed of air. Most polystyrene foams are incorporated and foamed with carbon dioxide. It is a polymer of the liquid monomer, styrene. They are excellent insulators and are lightweight, making their popular function as take out box packages. other than that, PS is also used in surfboards, car parts and stabilization systems.

The brittle and flammable property of Styrofoam is reduced by adding 5–10% butadiene rubber. So far, all styrene products are deemed safe.

7. Other plastics such as bioplastics and polycarbonate(PC)

Bioplastic is a type of biodegradable plastic that is formed from renewable biomass resources such as vegetable oil and corn starch rather than from non-renewable resources such as petroleum.

The other example is called polycarbonate. Polycarbonate is a group of thermoplastic polymers containing carbonate groups in their chemical structures. Polycarbonates are typically used for baby bottles, Sippy cups, water bottles, water gallons and metal food can liners.

However, a lot of countries have banned the use of this plastic material. The chemicals inside PC can be transferred into the food or beverages, which explains the reason behind the numerous health problems such as decreased sperm production in males, various behavioural changes, increased risk of breast cancer, prostate cancer, and metabolic disorders.

Infographics designed by Generation Earth Indonesia (@generationearth.id)

Written by Celine Lityo and Andrew Lim (@physicsociety)