What Makes Plastic Recyclable? Understanding Plastics in Simple Terms

Insights    Plastics 101

Highlights

  • Plastics come from either bio-based or synthetic sources.
  • Over 99% of global plastics are still made from fossil fuels.
  • Each plastic type has unique chemical & thermal properties.
  • These differences determine whether a plastic is recyclable.
  • The seven major plastic categories help sort materials—but most are still not recycled at scale.
  • Innovations like PX42™ enable viable recycling of mixed plastics beyond Types #1 and #2.

 

What Makes a Plastic Recyclable?

Understanding plastics begins with understanding where they come from and how they behave. When people ask, “What plastics are recyclable?” the answer depends on chemistry—not just collection programs. The everyday materials we call “plastic” are actually a diverse group of compounds with very different melting points, strengths, and chemical structures.

This article provides a simple overview to help consumers, policymakers, and industry professionals understand the basics behind recyclability.

 

Bio-Based vs. Synthetic Plastics

Plastics fall into two broad categories:

I. Bio-Based Plastics (Bioplastics)

These are made from renewable resources such as:

  • starch
  • carbohydrates
  • vegetable oils
  • plant-derived biomass

Bioplastics reduce fossil-fuel use, but they still represent less than 1% of all global plastics—and many are not recyclable in traditional systems.

II. Synthetic Plastics (Fossil-Based)

These dominate the market and are produced from:

  • crude oil
  • natural gas
  • coal

Even with increased attention on bio-plastics, more than 99% of plastic production still relies on synthetic feedstocks. These plastics form the foundation of global packaging, construction, transportation, healthcare, electronics, and virtually every industrial sector.

 

Why Plastics Differ So Much in Recyclability

Although we talk about “plastic” as a single material, plastics vary dramatically in:

  • melting point
  • flexibility
  • hardness
  • chemical resistance
  • porosity
  • ability to hold dyes or additives
  • behavior under heat

This complexity is why the question “Is plastic recyclable?” is rarely straightforward. A material may be technically recyclable—but not economically recyclable, or not compatible with existing municipal systems.  This is the root challenge behind global recycling rates remaining below 10%.

 

The Seven Main Plastic Categories

Plastic packaging often displays a resin identification code—commonly called a plastic recycling number. These seven categories help sort materials but do not guarantee that the item is recyclable.

Type 1 — PET (Polyethylene Terephthalate)

Common in beverage bottles. PET is the most widely recycled category and is one of the largest global sources of recycled plastic, supported by well-established collection and processing infrastructure.

Type 2 — HDPE (High-Density Polyethylene)

Used for jugs, detergent bottles, and rigid containers. Also widely recyclable.

Type 3 — PVC (Polyvinyl Chloride)

Found in pipes, medical tubing, and building products. Rarely accepted in recycling programs.

Type 4 — LDPE (Low-Density Polyethylene)

Used in grocery bags and films. People often ask, “Are plastic bags recyclable?”
Technically yes—but usually only through specialty film plastic recycling programs.

Type 5 — PP (Polypropylene)

Used in yogurt cups, closures, and automotive parts. Increasingly targeted for recycling, but still low recovery overall.

Type 6 — PS (Polystyrene)

Foam cups, trays, and packaging. Lightweight but difficult to recycle economically.

Type 7 — Other Plastics / Multilayer Composites

Includes bioplastics, engineered plastics, multilayer films, blends, and composites.
These are some of the least recyclable materials in today’s infrastructure.

 

Why So Many Plastics Aren’t Recycled Today

Mechanical recycling systems rely on highly sorted, clean, single-resin streams. But most real-world waste flows are:

  • mixed
  • contaminated
  • low value
  • multilayer
  • difficult to separate

This is where technologies like Transformix™ and PX42™ begin to redefine the answer to “What plastics are recyclable?”

Emerging solutions make it possible to process mixed plastics and hard-to-recycle categories—materials that historically ended up in landfills.

 

Frequently Asked Questions (FAQs)

Q1. Why can’t all plastics be recycled together?

A. Different plastics melt, react, and process at different temperatures. Mixing them often results in unusable output.

Q2. Why are PET and HDPE the most recycled plastics?

A. They have strong markets, stable chemistry, and well-established recycling infrastructure.

Q3. Are bioplastics recyclable?

A. Some are, but many degrade differently and cannot enter standard recycling systems.

Q4. What happens to plastics that aren’t recycled?

A. Most go to landfill or incineration unless advanced technologies can convert them into usable outputs.

Q5. What is the real meaning of the plastic recycling number?

A. The resin codes found on bottles and packaging—sometimes called recycled plastic numbers—identify the type of plastic used. They do not indicate whether your municipality will accept that material in its recycling program.

Q6. Can plastics from oceans or waterways be recycled?

A. Yes—although ocean plastics are often degraded, mixed, or contaminated, they can still be recovered and processed using specialized approaches. Traditional recycling systems cannot handle these materials, but technologies such as Plastonix make ocean plastic recycling possible by converting low-value debris into usable outputs.

To explore how Plastonix technology enables recycling of mixed or low-value plastics, Contact Us today.

 

Sources

  1. Plastics Europe – Plastics Manufacturing & Resin Identification Codes. Plastics Europe
  2. EPA – Plastics: Material-Specific Data. EPA
  3. NAPCOR – PET Recycling Data. NAPCOR