How can we visually distinguish PP, PE, PET, and PETG?

In the cosmetics industry, the most commonly used material is plastic, and among the plastic materials, the most common ones are PP, PE, PET, and PETG.
How can we distinguish these materials visually? Here are a few simple methods that I've summarized for you:

㈠ . Look at the Bottom of the Bottle

Why? It's because some bottle bottoms will directly indicate the material used.  

Even if it's not written, different materials will have some distinct differences at the bottom due to the different molding processes used, which can be used for identification.

Generally speaking, PET bottles will have a larger circular material point at the bottom, while PP bottles will have a small dot. PETG bottles, on the other hand, will have linear protrusions at the bottom.

㈡ . Observing the Appearance

Mainly by looking at whether the bottle is transparent and smooth:
PET bottles have high transparency and can be both matte and glossy. Common mineral water bottles are made of PET material.
PP bottles are usually semi-transparent and can also be either matte or glossy. However, they are softer than PET and are more suitable for packaging that requires squeezing, such as shampoo bottles.
PE bottles are basically opaque and have a rough surface, generally matte.

In terms of transparency: PETG > PET (transparent) > PP (semi-transparent) > PE (opaque)
In terms of smoothness: PET (glossy/matte) > PP (glossy/matte) > PE (matte)

㈢.  Interpretation of the Icon on the Bottom of the Bottle

  ●  "# 1" PET/PETE  (Polyethylene Terephthalate)

Properties: PET is known for its clear and strong nature, making it ideal for packaging. Heat-resistant up to 70℃. Excellent at protecting contents from moisture and gases. Easy to transport and handle.

Usages: Widely used for beverage bottles, food containers, and cosmetic bottles/ Converted into fibers for fabrics and clothing/ Used in 3D printing filaments and engineering resins.

Recycling and Sustainability: PET can be recycled multiple times without significant degradation. PET can be recycled multiple times without significant degradation. Many companies are committed to using rPET to promote sustainability.

  ●  "# 2" HDPE (High-Density Polyethylene)

Properties: HDPE is a durable, strong, and lightweight plastic known for its resistance to impact, chemicals, and moisture. It is opaque in appearance and exhibits excellent tensile strength, making it suitable for various applications.

Usages: HDPE finds widespread use across different industries. It is commonly utilized in packaging for products such as detergent bottles, milk jugs, and shampoo containers due to its excellent chemical resistance. Additionally, it is employed in the construction sector for pipes, fencing, and geomembranes due to its durability and corrosion resistance.

Recycling and Sustainability: HDPE is highly recyclable and contributes significantly to the circular economy. It can be recycled into a wide range of products, including new bottles, pipes, and plastic lumber. Its robust nature ensures that it retains its properties through multiple recycling cycles. Additionally, HDPE recycling saves energy and resources compared to producing new plastic. Many companies and municipalities promote HDPE recycling initiatives to reduce waste and environmental impact.

 ●  "# 3" PVC  (Polyvinyl Chloride)

Usages: Pipes, window frames, flooring. Medical devices and packaging. Cleaning product bottles, and food wrap. Insulation for wires and cables. Additionally, PVC is used in packaging for products like cleaning agents, food wraps, and blister packaging.

Containers of this material are now used relatively rarely for packaging food. If in use, do not expose it to heat. 

Recycling and Sustainability: Recycling PVC can be challenging due to the presence of additives and the need to separate it from other plastics. Yet, progress in recycling technologies has made PVC recycling increasingly viable. Recycled PVC can be used in various applications, including pipes, flooring, and packaging materials. Sustainability efforts in the PVC industry focus on reducing environmental impact through improved manufacturing processes, waste reduction, and promoting recycling initiatives. Additionally, there is ongoing research into bio-based and biodegradable alternatives to conventional PVC to further enhance sustainability.

 ●  "# 4" LDPE (Low-Density Polyethylene)

Properties: LDPE is a flexible and lightweight plastic known for its toughness, chemical resistance, and moisture barrier properties. It has a relatively low melting point and is translucent to opaque in appearance. LDPE exhibits excellent flexibility and elongation at break, making it suitable for applications requiring stretchability 

Usages: LDPE is widely utilized across various industries due to its versatility and favorable properties. In the packaging sector, it is commonly used for plastic bags, shrink wraps, and flexible packaging films due to its excellent sealing properties and resistance to tearing. In the agricultural industry, LDPE is employed for greenhouse films, mulch films, and irrigation tubing due to its durability and resistance to environmental factors. Additionally, LDPE is used in the manufacture of squeeze bottles, toys, and wire insulation due to its flexibility and low cost

Recycling & Sustainability: LDPE is recyclable but typically has a lower recycling rate compared to other plastics like PET and HDPE. It can be recycled into various products, including plastic lumber, irrigation pipes, and trash can liners. Sustainable practices in LDPE recycling involve promoting collection and sorting initiatives to increase recycling rates. Additionally, there is growing interest in developing biodegradable alternatives to conventional LDPE to reduce environmental impact and promote sustainability.

 ●  "# 5" PP (Polypropylene)

Properties: PP is a versatile plastic known for its excellent chemical resistance, high melting point, and durability. It has a low density, making it lightweight yet strong. PP is rigid and tough, with good resistance to fatigue and cracking. It also has excellent heat resistance and can withstand high temperatures. 

Recycling & Sustainability: PP is considered one of the more recyclable plastics and has a relatively high recycling rate compared to other plastics. It can be recycled into various products, including automotive parts, garden furniture, and containers. Sustainable practices in PP recycling involve promoting collection programs and sorting initiatives to increase recycling rates. Additionally, there is growing interest in developing bio-based PP and improving mechanical recycling technologies to enhance sustainability and reduce reliance on fossil fuels.

 ●  "# 6" PS (Polystyrene)

 Properties: Polystyrene is a versatile plastic known for its clarity, rigidity, and lightweight nature. It can be transparent or colored, and it has good insulation properties, making it suitable for both hot and cold applications. PS is rigid and brittle, with low moisture absorption and excellent chemical resistance 

Usages: PS is widely used across various industries due to its favorable properties. In the food packaging sector, it is commonly used for disposable cups, plates, and food containers due to its lightweight nature and insulation properties. In the electronics industry, PS is employed for packaging electronic components and devices due to its shock-absorbing properties. Additionally, PS is used in the construction industry for insulation panels and packaging materials

Recycling & Sustainability: PS recycling can be challenging due to its lightweight and low density, which can make it uneconomical to transport and process. However, advancements in recycling technologies have made PS recycling more feasible. Recycled PS can be used in various applications, including packaging materials, insulation, and decorative items. Sustainable practices in PS recycling involve promoting collection programs and sorting initiatives to increase recycling rates. Additionally, there is growing interest in developing biodegradable alternatives to conventional PS to reduce environmental impact and promote sustainability.

 ●  "# 7" Other Plastics

Some baby bottles, and water jugs. Electronic components, CD cases. Medical devices, laboratory equipment. High-performance automotive parts. Eyeglass lenses, sports equipment

Conclusion

Different types of plastic are widely used across various industries due to their unique properties and advantages. Understanding these plastics and their applications helps us appreciate their role in daily life and the importance of recycling. Making informed choices about plastic use and recycling can contribute to a more sustainable future.