How Many Types of Plastic Can a Plastic Sorter Separate? A Complete Guide

Plastic sorting machines have become indispensable in modern recycling facilities, enabling the efficient separation of diverse plastic types for reuse. But just how many types of plastic can these advanced systems distinguish? The answer depends on the technology employed, the complexity of the plastic mixture, and the desired purity of the output. This guide explores the capabilities of plastic sorters, the technologies behind them, and the real-world applications that make circular plastic recycling possible.

The Fundamentals: Plastic Resin Codes and Sorting Challenges

Most consumers recognize the 7 resin identification codes (1-7) stamped on plastic products, each representing a distinct polymer type. However, modern plastic sorters can often distinguish beyond these broad categories, identifying sub-types and even blended materials. The primary challenge lies in separating plastics with similar physical properties—such as polyethylene (PE) and polypropylene (PP), which have nearly identical densities—or dark-colored plastics that absorb light, hindering detection.

Common Plastic Types Separated by Sorters

Plastic sorters typically handle the following primary polymer families, with advanced systems capable of further细分:

Key Technologies Behind Plastic Sorting

Modern plastic sorters combine multiple technologies to identify and separate plastics based on their chemical composition, physical properties, and optical characteristics. Here’s how each technology contributes to sorting capabilities:

1. Near-Infrared (NIR) Spectroscopy

NIR spectroscopy is the workhorse of plastic sorting, capable of identifying most polymers by their unique “chemical fingerprint.” When NIR light hits a plastic particle, specific wavelengths are absorbed based on molecular bonds (e.g., C-H, O-H). Sensors detect these absorption patterns, allowing the system to classify plastics like PET, HDPE, and PP with 95-99% accuracy for common types.

Limitations: Struggles with black or dark-colored plastics (which absorb NIR light) and multi-layered materials (e.g., juice boxes with PE/PET layers).

2. Electrostatic Separation

This technology exploits differences in how plastics acquire electric charge when rubbed against each other (triboelectric effect). For example:

• PE tends to gain a negative charge.
• PP typically acquires a positive charge.

In an electric field, charged particles deflect toward oppositely charged electrodes, separating mixtures like PP/PE with 90-95% purity. This is critical for recycling caps and closures, where PP and PE are often mixed.

3. Density-Based Separation (Sink-Float Tanks)

Using water or salt solutions of varying densities, this method separates plastics by buoyancy:

• PET (density ~1.38 g/cm³) sinks in water.
• PP/PE (density ~0.90-0.96 g/cm³) float.

Simple but effective, it’s often used as a pre-sorting step to separate heavy plastics (PET, PVC) from lighter ones (PP, PE).

4. AI-Powered Optical Sorting

Advanced systems integrate high-resolution cameras, machine learning algorithms, and multi-spectral sensors to identify plastics by color, shape, and even surface texture. For example:

• Tomra’s Innosort Flake™ uses AI to separate black plastics by analyzing subtle differences in reflectivity.
• AMP Robotics’ Cortex™ system learns to distinguish rare plastics (e.g., POM, PC) by training on millions of images.

These systems can handle 12+ distinct plastic types in complex waste streams, including contaminated or fragmented materials.

Real-World Capabilities: Case Studies

Industrial plastic sorters demonstrate impressive versatility in real recycling facilities:

Case 1: Separating PET from PVC in Bottles

At a European recycling plant, a Sesotec Varisort N system uses NIR spectroscopy to separate PET bottles from PVC labels. The system achieves 99.9% PET purity, critical for food-grade recycling. Contamination with PVC (even at 0.1%) can render recycled PET unfit for new bottles.

Case 2: Polyolefin Separation (PP/PE)

California-based Greenpath Enterprises deployed a Tomra Innosort Flake™ system to separate PP caps from PE bottles. By combining NIR and electrostatic technologies, the system achieves 95% purity for both PP and PE, enabling “cap-to-cap” recycling—a first for the industry.

Case 3: Multi-Layer Packaging

A Swiss facility uses hyperspectral imaging to sort multi-layer films (e.g., PE/PET/Aluminum). By analyzing light across 200+ wavelengths, the system identifies individual layers and separates them with 85-90% efficiency, a task previously considered impossible with mechanical sorting.

Challenges and Limitations

While modern sorters are powerful, several factors limit their capabilities:

• Contamination: Food residue, labels, or non-plastic materials (e.g., metals, glass) can confuse sensors. Commercial recycling streams average 14% contamination, reducing sorting efficiency.
• Black Plastics: Carbon black pigments absorb NIR light, making identification difficult. New systems use laser-induced fluorescence (LIF) or Raman spectroscopy to overcome this.
• Small Particles: Microplastics (<10mm) are harder to detect, with accuracy dropping to <90% for particles under 5mm.
• Cost: Advanced multi-sensor systems can cost $200,000–$500,000, limiting adoption for small recyclers.

Future Trends: Beyond 7 Types

Emerging technologies promise to push sorting capabilities further:

• Digital Watermarks: Embedded invisible codes in plastic packaging allow sorters to identify polymers, even in black or multi-layered products.
• AI-Driven Adaptation: Systems like Machinex’s SamurAI learn from operator feedback, improving accuracy for rare plastics over time.
• Chemical Tracers: Additives like Nextek’s PolyPrism™ fluoresce under specific light, enabling sorting of otherwise indistinguishable plastics.

These innovations could soon allow sorters to reliably separate 20+ plastic types, including bioplastics and engineering resins like POM (polyoxymethylene) and PC (polycarbonate).

Conclusion: The Role of Sorters in Circular Economy

Plastic sorters are not just machines—they are the backbone of a circular plastic economy. Today’s systems can separate 7–12 primary plastic types with high purity, while advanced setups handle 15+ types for specialized applications. As technology evolves, the question will shift from “how many types” to “how efficiently,” making plastic recycling more viable and sustainable than ever.

For recycling facilities, investing in multi-technology sorters (NIR + electrostatic + AI) is key to maximizing material recovery and meeting strict purity standards. For consumers, proper waste separation remains critical—even the best sorters struggle with heavily contaminated streams. Together, technology and consumer awareness will drive the next leap in plastic recycling.