Turning ALS2 non-metallic residues into useful plastic filler
Recovering precious metals from electronic waste leaves more than a metal-rich fraction. The remaining non-metallic material can contain glass fibres, mineral particles, ceramics, polymer fragments and other finely divided components from printed circuit boards and electrical equipment. With suitable characterisation, this residue may become a secondary raw material rather than a disposal burden.
The granularity of ALS2 non-metallic residues is central to that opportunity. Particle size influences how a residue flows, disperses, mixes with polymer, affects surface appearance and changes the mechanical performance of a finished plastic compound. A material that is well suited to a rigid moulded part may be unsuitable for a thin film or a highly finished consumer product.
For Australian recyclers, compounders and manufacturers, this question connects technology with practical market conditions. E-waste may travel long distances between collection points, dismantling operations and processing facilities, while customers in Sydney, Melbourne, Brisbane and Perth increasingly expect recycled content with credible environmental and technical documentation.
Why particle size matters in plastic compounds
A filler is incorporated into a polymer to adjust cost, stiffness, density, dimensional stability, appearance or other properties. The particle size distribution determines how efficiently the solid phase occupies space within the plastic. Coarse particles can create a rough surface and stress concentration, while very fine particles can agglomerate, increase viscosity and demand more intensive mixing.
Granularity also affects feeding and handling. A consistent powder or granulate can move through hoppers and dosing equipment more reliably than a broad mixture containing dust, flakes and larger fragments. Excessive fines may create dust, bridge in silos or separate from larger particles during transport. Oversized pieces can block screens, damage equipment or remain visible in the moulded product.
For ALS2 residues, particle size should be assessed together with particle shape. Angular glass or ceramic particles behave differently from rounded mineral grains, even where both pass the same sieve. Flat flakes may orient during injection moulding, whereas irregular dust may pack into voids or form clusters. A useful specification therefore needs more than a single average diameter.
From recovered residue to a controlled feedstock
The non-metallic fraction should first be described through a particle size distribution, typically using a sequence of sieves for coarser material and laser diffraction or another suitable method for finer material. Results can be reported as d10, d50 and d90 values, which indicate the sizes below which 10, 50 and 90 per cent of the particles fall.
These figures help a plastics processor compare batches and choose equipment. A narrow distribution may support predictable dosing, while a deliberately blended distribution may improve packing and reduce voids. Neither approach is automatically better. The right profile depends on the polymer, filler loading, processing temperature, screw design and appearance requirements of the end product.
Screening, air classification, milling and de-dusting can refine ALS2 non-metallic residues. Such operations should be balanced against energy use, yield loss and the need to preserve the sustainability advantage of acidless separation. A practical process may separate an oversize fraction for additional treatment, recover a useful middle fraction for compounding and manage very fine dust under appropriate occupational and environmental controls.
Matching granularity with plastic applications
Coarser residue fractions may be considered for robust, dark or textured products where a small variation in colour and surface finish is acceptable. Potential examples include pallets, transport components, cable management products, tool housings and non-visible infrastructure parts. In these applications, stiffness and dimensional performance may be more important than a perfectly smooth surface.
Finer fractions can offer a more uniform appearance and may disperse more effectively in selected thermoplastics. They can be relevant to injection-moulded housings, sheet products and compounds where the filler must be less noticeable. Fine material can still cause problems if it carries moisture, has a high surface area or contains particles that attract one another during blending.
The polymer matrix also changes the result. Polypropylene, high-density polyethylene, acrylonitrile butadiene styrene and recycled engineering plastics each respond differently to mineral or glass-rich filler. Compatibilisers, coupling agents and impact modifiers may improve bonding, though these additions affect cost and recyclability. Trials should measure tensile strength, impact resistance, flexural modulus, shrinkage, density, melt flow and surface quality rather than relying on granularity alone.
| Residue fraction or condition | Likely processing behaviour | Suitable direction for testing | Main control point |
|---|---|---|---|
| Oversize particles and flakes | Poor feeding and visible defects; possible equipment blockage | Re-screening, re-milling or use in coarse, dark compounds | Maximum particle size and foreign-object removal |
| Controlled medium fraction | Easier dosing and useful stiffness contribution | Rigid moulded products, pallets, housings and profiles | Consistent particle distribution and moisture |
| Fine fraction | Better potential for surface uniformity but higher dust and agglomeration risk | Higher-quality compounds after dispersion trials | Dust control, surface chemistry and mixing energy |
| Broad, unsorted distribution | Variable flow, packing and final properties | Preliminary screening only | Batch segregation and tighter classification |
| Moist or contaminated material | Defects, odour, corrosion or polymer degradation | Drying and additional quality assessment before use | Moisture, residual metals and hazardous substances |
Quality controls that support reliable use
Granularity is one part of a broader feedstock specification. Each batch should be checked for moisture, bulk density, ash or mineral content, residual metals, halogens where relevant, organic contaminants and visible foreign matter. The exact test program depends on the source stream and the intended plastic article.
Electronic waste is heterogeneous. A batch derived mainly from circuit boards may differ considerably from material containing appliance plastics, cables or mixed WEEE. Trace metals that are valuable during recovery can still matter in the residue if they affect colour, odour, electrical behaviour or regulatory classification. Representative sampling is essential because a small grab sample may not reflect a full container or production run.
Australian processors will also need to consider workplace exposure and transport. Fine particulate material should be handled with suitable extraction, enclosure and personal protective measures. At a facility in western Sydney or Melbourne’s industrial north, the practical requirements may include sealed packaging, dust monitoring and documented chain-of-custody procedures. Long-distance freight to Queensland or Western Australia makes moisture protection and batch identification especially important.
Proving performance in Australian manufacturing
A sensible qualification pathway begins with a small, well-characterised sample. The residue can be dried, screened into defined fractions and compounded at several loading levels. The resulting pellets or moulded plaques can then be compared with an unfilled polymer and an established commercial filler such as calcium carbonate, talc or glass fibre.
Testing should reflect the market being targeted. A compound intended for outdoor products in Queensland may need accelerated weathering, moisture exposure and impact testing. A material for automotive or electrical housings may require tighter control of odour, flammability, dimensional stability and surface finish. For products made in Victoria or New South Wales, customer specifications and recycled-content claims may be just as influential as laboratory results.
Local collection and manufacturing arrangements also shape commercial viability. Councils in South Australia, Western Australia and the Australian Capital Territory may direct household e-waste through different contractors and programs. A recycler planning a national supply chain must account for varying collection volumes, transport distances and state-based environmental expectations. Building a dependable specification around particle size helps convert a variable stream into a feedstock that compounders can purchase with confidence.
Designing a circular route for the residue
The strongest application is unlikely to come from treating every ALS2 non-metallic residue as an identical filler. Instead, separate grades can be developed around particle size, composition and performance. A fine, clean fraction may serve one compounder, while a coarser or more variable fraction may suit a different product with less demanding visual requirements.
This approach can improve resource efficiency across the recovery plant. It reduces the amount sent to disposal, creates additional value from electronic waste and supports a clearer account of material flows. The acidless nature of ALS2 technology is especially relevant when the objective is to develop safer and cleaner precious-metals recovery alongside practical pathways for secondary materials.
Ikoi S.p.A.’s ALS2 project can help interested recyclers, plastics companies and research partners assess where residue classification fits within a compact precious-metals recovery plant. Technical evaluation should include representative sampling, particle-size analysis, compounding trials and end-product testing. Contact the ALS2Project team to discuss a pathway for characterising non-metallic residues and identifying suitable Australian plastics applications.