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The Importance of Material Separation in 3D Filament Recycling

Introduction: Sustainability and Precision in 3D Printing

3D printing is a powerful tool, but filament waste – such as media, failed prints or leftovers – presents an environmental challenge. At Tucab, we believe in recycling as a solution, but we emphasize the critical need to separate different types of materials, such as PLA, ABS, PETG and EVA, before the process. Mixing them not only compromises quality, it can contaminate the material, making it useless and destined for waste. This article details the technical characteristics of the materials, the recycling process and the reasons why separation is essential.

Technical Characteristics of Materials and Mixing Risks

Tucab filaments are thermoplastic polymers with specific properties that make them ideal for different applications. Mixing them during recycling creates serious technical problems. Here are the detailed characteristics and reasons to avoid contamination:

Thermal and Melting Properties
- PLA:
  - Melting temperature: 180-220°C
  - Glass transition temperature (Tg): ~60°C
  - Thermal degradation: >250°C, releasing gases such as lactic acid.
- ABS:
  - Melting temperature: 220-260°C
  - Tg: ~105°C
  - Degradation: >270°C, with styrene emissions (toxic).
- PETG:
  - Melting temperature: 220-240°C
  - Tg: ~85°C
  - Degradation: >260°C, with lower emission of volatile compounds.
- EVA:
Risk: Mixing PLA (low Tg) with ABS (high Tg) in an extruder at 240°C, for example, degrades the PLA, creating bubbles and impurities in the filament. This contamination makes the material brittle and unusable, going directly to waste.
Molecular Structure and Chemical Compatibility
- PLA: Aliphatic, hydrophilic polyester, with short linear chains (Mw ~100,000-200,000 g/mol).
- ABS: Copolymer with distinct phases (acrylonitrile, butadiene, styrene), hydrophobic, Mw ~100,000-150,000 g/mol.
- PETG: Polyester modified with glycol, semi-hydrophilic, Mw ~50,000-100,000 g/mol.
- EVA: Copolymer of ethylene and vinyl acetate, highly flexible, variable Mw (~50,000-120,000 g/mol).
Risk: Chemical incompatibility prevents the formation of a mixture homogeneous. For example, PLA does not bond with ABS due to differences in polarity, resulting in a filament with separate phases that is weak and prone to failure. This contamination compromises structural integrity, making reuse unfeasible.
Mechanical Properties
- PLA: Tensile strength ~50 MPa, elongation ~5%, brittle.
- ABS: Tensile strength 40-60 MPa, elongation ~10-50%, resilient.
- PETG: Tensile strength ~50 MPa, elongation ~20-70%, flexible.
- EVA: Tensile strength <20 MPa, elongation >100%, elastic.
Risk: A mixture of PLA and EVA, for example, creates a filament with reduced resistance (<30 MPa) and unpredictable elongation, unable to withstand loads or function as an elastic material. This inconsistency leads to the total discard of the contaminated batch.
Printing Behavior
- Diameter: Tucab filaments are 1.75 mm or 2.85 mm (±0.05 mm).
- Flow: PLA has low viscosity, ABS medium-high, PETG medium, EVA low-high (depending on the composition).
Risk: Mixtures alter the flow in the extruder, causing diameter variations (e.g.: >0.1 mm), clogging and failures in adhesion between layers. The contaminated material becomes unpredictable and is rejected for printing.
Environmental Contamination and Waste

Mixing PLA (biodegradable) with ABS or PETG (non-biodegradable) eliminates the ecological advantage of PLA, creating a hybrid which cannot be composted or recycled efficiently.
Risk: A contaminated batch, with no technical or environmental value, is discarded in landfills, increasing the environmental impact and defeating the purpose of recycling.

The 3D Filament Recycling Process

The process of transforming waste into new filaments requires technical precision. Initial separation is the most critical step to avoid contamination. Here is the detailed process:

Collection and Separation
- Method: Waste is classified by type using visual identification (e.g., glossy PLA, matte ABS), labels on the reels, or thermal testing (e.g., PLA softens the ~60°C, ABS at ~105°C).
- Specifications: Manual or automatic separators (e.g. infrared sensors) identify materials with 95% accuracy.
- Justification: Avoids the introduction of chemical or thermal impurities from the beginning.
Crushing
- Equipment: High-speed crushers (e.g. Filabot Wee, 500-1000 rpm) produce 2-5 mm granules.
- Parameters: Speed adjusted to avoid excessive heating (e.g. <100°C for PLA).
- Control: Granules must be uniform in size (±0.5 mm) for consistent extrusion.
- Note: Each material is processed separately to avoid particle mixing.
Cleaning and Drying
- Cleaning: Washing with water at 30-40°C and neutral detergent removes contaminants (e.g.: dust, oils).
- Drying: Vacuum ovens (e.g.: 0.1 bar) at 50-60°C (PLA), 80-100°C (ABS) class="break-words">Extrusion
  - Equipment: Precision extruders (e.g. 3devo Composer) with heating zones (3-5 zones).
  - Technical Parameters:
    - PLA: 190-210°C, pressure 10-15 bar, speed 5-10 m/min.
    - ABS: 230-250°C, pressure 15-20 bar, emissions ventilation (0.1-0.5 mg/m³ styrene).
    - PETG: 230-245°C, pressure 12-18 bar, slow cooling.
    - EVA: 200-220°C, pressure 8-12 bar, adjust for elasticity.
  - Control: Lasers measure diameter in real time (tolerance ±0.03 mm), with cooling in a water tank at 20-30°C.
  - Mixing Risk: Inadequate temperatures (e.g.: 240°C for PLA+ABS) degrade the PLA, contaminating the ABS with carbonized residues.
- Winding
  - Machine: Automatic winders with tension of 1-2 N, producing coils of 0.5-1 kg.
  - Specification: Constant diameter, without overlaps (deviation <0.1 mm).
  - Labeling: Ex.: "Recycled PLA – Tucab, 1.75 mm".
- Final Test

Impact of Contamination: From Trash to Total Waste

Mixing materials results in a cascade of problems:

Thermal Degradation: PLA carbonizes at ABS temperatures, creating visible impurities (black spots).
Mechanical Inconsistency: A PLA+PETG filament can break at <20 MPa, making it useless for any application.
Print Rejection: Flow variations and clogging (e.g. 0.4 mm nozzle blocked) waste time and energy.
Final Destination: With no technical value, the contaminated material goes to landfills, losing up to 100% of its recycling potential.

Benefits of Correct Separation and Recycling

Quality: Pure recycled filaments have performance close to the original (e.g. recycled ABS with 90-95% of the properties of new).
Efficiency: Up to 80-90% of waste is reused, reducing costs and emissions (e.g. ~0.5 kg CO₂/kg recycled vs. 2 kg CO₂/kg new).
Sustainability: Preserves ecological characteristics (e.g., compostable PLA).

Conclusion: A Commitment to Quality and the Environment

At Tucab, recycling 3D filaments is a priority, but it depends on the rigorous separation of PLA, ABS, PETG and EVA. Mixing them not only destroys the quality but also contaminates the material, sending it to waste and nullifying the environmental benefits. With advanced technical processes, we transform waste into reliable filament – but we need your help to separate it from the start.

Want to know more about our recycling process? Check out all the details of the Fil2ndLife project at https://mailchi.mp/tucab.pt/fil2ndlife-projeto-reciclagem-desperdicios-impressao-3d-plastico and join us on this sustainable mission! Also visit tucab.pt for more information.

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