A sweet story of recycle logo and plastic

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Sweet Recycling logo story

The recycling logo is widely accepted and call as a universal symbol of recycling.

It is apparent on packaging and products in your business, and home, your retail shops, restaurants plastic made items, and, of course, waste disposal services. The recycling symbol can be seen embossed on the bottom of rigid plastic and imprint on flexible film’s surface.  

The symbol consists of a triangle of three arrows looping back into each other, what’s known as the Mobius Loop. Although the original and most widely recognized design incorporates green arrows, modifications have been made since its origin, which sees white with black outlines or blocks black color used instead and conveys different meanings.

Origin of Recycling Logo

The symbol was founded in the 70s, ahead of the first-ever Earth Day. On that day, the USA was challenged to design something that raised awareness of environmental issues.
The winner, Gary Anderson, created what’s now known as this symbol, and the rest is history.
So every plastic has been nominated with a designated number.

What is Plastic? 

Plastics are produced by the process of polymerization, which may be either addition or condensation polymerization.
Plastics are defined as any group of natural or synthetic substances, consisting chiefly of polymers of high molecular weight, that can be molded into a shape or form by heat and pressure. They usually consist of large organic materials molecules based on specific building block molecules referred to as monomers. When these monomers, which are relatively small molecules, undergo a process known as polymerization, a plastic or long-chain polymer is produced.

Here a list of plastic(Thermoplastic resin) with their recycle number: 

#No1  PET

Scientist – Nathaniel Wyeth, 1973

Process – Blown Film Extrusion, Injection Stretch Blow Moulding

The interaction of acids and alcohol forms polyesters. The reaction is a condensation polymerization process, producing an ester and releasing water. Commonly used films (for tapes) are formed by dimethyl terephthalic acid and ethylene glycol to give polyethylene (glycol) terephthalate. PET films are incredibly tough and very tear-resistant. Polyester has found wide application for 1–3 l stretch blown containers and pharmaceutical and cosmetic/toiletry usages as small moldings.


  • Plastic Bottle for soda, water, etc.
  • Food Jar 
  • Microwavable food trays
  • Textile, carpets
  • Strapping and films

#No2 HDPE 

Scientist – Ziegler, 1963
Process – Blown Film Extrusion, Injection Moulding, Extrusion Blow Boulding, Compression Moulding, Roto Moulding 
HDPE is the most crystalline material (around 95%) and virtually free of branching and, as a result, has the best chemical properties, i.e., best resistance and lowest permeabilities. It is also a relatively rigid, tough material with the lowest clarity.


  • Bottles for milk, water, juice, cosmetic, shampoo, laundry detergents, and household cleaner
  • Grocery bags and cereal box liner
  • Extruded pipe, composite plastic, wire, and cable covering 

#No3 PVC

Scientist – Eugen Baumann, 1872
Process – Film Extrusion, Injection Moulding, Extrusion Blow Boulding
This group covers polyvinyl chloride (PVC), polyvinylidene chloride (PVdC), polyvinyl acetate, and polyvinyl alcohol, each with packaging applications. When PVC is used for general pharmaceutical applications, the factors include plasticizers, stabilizers, modifiers, monomer residues, regrind, lubricants, catalytic residues, and chain length.


  • Rigid Packaging 
  • Shrink Wrap and stretch wrap
  • Cable insulation, carpet backing, flooring


Scientist – Eric Fawcett, 1933
Process – Blown Film Extrusion, Injection Moulding, Extrusion Blow Boulding, Compression Moulding
Low-density polyethylene material has branched chains and limited crystallinity, leading to an open structure and low density. It is remarkably soft and flexible, transparent to translucent, has good impact resistance and relatively low melting points, which give good heat sealability.


  • Bags for dry cleaning
  • Toys
  • Squeezable Bottle
  • Sealant layer
  • Frozen food packaging

#No5 PP

Scientist – Giulio Natta, 1954
Process – Blown Film Extrusion, Injection Moulding, Extrusion Blow Boulding, Compression Moulding
Polypropylene is somewhat similar to HDPE in general properties. It exists as a homopolymer and a copolymer with ethylene and other hydrocarbons. It can also be blended with polyisobutylene. PP is one of the lowest density plastics, translucent to natural milky white with a highly crystalline structure. PP homopolymer has poor low-temperature resistance.


  • Yogurt and Dahi packaging cups
  • Medicine Bottle
  • Ketchup Bottle
  • Syrup bottle
  • BOPP Tapes

#No6 Polystyrene

Scientist – BASF, 1930
Process – Film Extrusion, Injection Moulding, Extrusion Blow Boulding
The monomer has a chemical similarity to propylene in that benzene rings replace the methyl (CH3) groups. It is a transparent rigid hard material with good tensile strength and more brittle plastics when dropped or flexed. PS is reasonably resistant to mineral oils, water, and alkalis but soluble in hydrocarbon solvents. Hence it can be solvent welded (plastic model kits). Polystyrene is relatively permeable to moisture and is not generally a suitable packaging material for pharmaceutical products. To improve the brittle characteristic, materials are frequently impact modified with rubber polymers, polybutadiene, and styrene-butadiene (SBR) by either blending or graft polymerization.


  • Cups, plates, bowls, takeout container
  • Form Packaging
  • Compact disc case 
  • Medical bottles

#No7 Other Plastic 

The plastic falls in the category of other recycling, i.e., Polyamide, Polycarbonate, composite plastic(Bi-laminated or may be tri-laminated), and many other “n” numbers of plastic. I do not get any specific information about why we have not given the exact number to every plastic category. Even the Chinese have shown a particular number for every plastic. Source: Wikipedia 
A big question on recycle 7!!!
Why can’t we give the specific number to the other category of plastic?   
The identification number is there on the plastic container and film, i.e., from 1 to 7 number. But don’t you think it needs to be more specific for the other category (i.e., 7no.) plastic. Typically, we imprint on the plastic surface as per material property either by embossed or surface printing. If the plastic container is made with the LDPE plastic, we give four numbers with a recycled symbol. But, what about other plastic category recycle number 7. 
For any recycling, the first requirement to identify the plastic character, and then only we can proceed for the particular plastic grade recycling.
Plastic recycling is means with the Kerbside recycling program. Click on the Wikipedia link.
But if we put recycling number 7, a recycler person is not able to get about the plastic category, whether it’s biodegradable, composite, recycled, and compost plastic.
The 7 number is given to all types of plastic, which is not falling in the top 6, i.e., PA, PC, composite or co-ex plastic.

Why recycler has issues during curbside recycling?

During plastic recycling, the recycler department has to separate the plastic on their category basis, such as LDPE or PET plastic. We can not mix the plastic with the other category of plastic. The category plastic from 1 to 6 has definite recycling in their class and can be easily differentiated with the recycling symbol with their number.

Recycling process from 1 to 6 number of plastic 

The recycler person performs the recycling process and forms the recycled plastic granules with the recycling curbside program. The recycled granules then send to the bottle and film manufacturer; the production department uses recycled pellets with the virgin material based on the requirement. The market trend is 15 to 20% recycled plastic, 5 to 10% pinch of plastic, and 75 to 80% virgin material. But again, this is on the agreed condition between the supplier and client approval.
So, what to do with recycle 7 plastic?
As we have seen, so much plastic falls in the other plastic category and cannot mix the other plastic. 
But again, if we want to recycle plastic number 7, what will be the recycling methodology? Can we use the recycling process as such conventional methods? 
The answer is no.
Many other websites are there, which consider PLA as 7 recycled plastic. For plastic or packaging engineer, I will leave a question for you.  

Can we recycle PLA plastic?

I will give you a reference. Read Here The Association of Plastic Recyclers
Kindly leave your comment, what you think about PLA recyclability. 

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