ENStarting point
Compatibilisation is a material development strategy, not permission to mix any waste. The decision depends on the polymers present, variability, processing, application and cost per approved product.
Distinguish a formulated blend from contamination
A formulated blend has defined components, proportions and acceptance criteria. A contaminated stream may have compositions that change without control. The difference is more than a name: it determines whether processing can be repeated and whether the test result represents the supply. Before considering an additive, describe the material that will be available month after month.
For plastics from electronic scrap, separate families, origins and preparation conditions. Record pigments, fillers and information on additives where available. A predominant identification as ABS does not automatically describe the minor fraction. Batch sampling should enable assessment of both average composition and the presence of subgroups that require separate treatment.
Interpret studies without copying a recipe
A study published in 2018 investigated the use of styrene-butadiene rubber in blends of HIPS and ABS from WEEE, comparing blend properties with and without the modifier. The result demonstrates a line of investigation for defined materials; it does not establish a universal proportion for every recycled HIPS/ABS stream. [1]
Another study analysed ABS with 4% PP by mass and assessed mechanical behaviour and modelling, including a compatibilisation strategy. [2] The chosen composition belongs to the study. It should not become a general contamination tolerance limit. Part geometry, loading type, formulation and processing can change the response. Use the literature to select hypotheses and tests, keeping qualification tied to the actual material.
Start with the part's requirements
Define which properties must be preserved and which allow adjustment. One application may be limited by impact, another by deformation, service temperature, finish or weld lines. The average strength of a test specimen does not describe all these behaviours. Organise a matrix of requirements, methods, preparation conditions and acceptance criteria before comparing formulations.
Include use and market requirements. A change that improves impact performance may alter stiffness, flow, colour or cost. For parts with electrical functions or other specific requirements, check whether additional assessments are needed. Development should not proceed merely because the material has become “stronger”; it must meet all the requirements that make the part suitable for its function and manufacturing process.
Design an experiment that reveals the additive's effect
Use the unmodified material as a reference and, where relevant, the resin currently qualified for the part. Compare formulations under controlled drying, feeding, extrusion, moulding and conditioning conditions. Keep samples and records of each batch. If preparation varies between groups, it will be difficult to tell whether the gain came from the additive or another process difference.
Plan composition and dosage variations within a technically justified range. The protocol should include repeats and result dispersion, not just the best value. Where several variables may interact, experimental design can help separate their effects. Avoid testing dozens of recipes without a clear hypothesis: a smaller, well-documented sequence can produce a more useful decision and reduce sample waste.
State the basis of the proportions
The unit phr means parts per hundred parts of resin and is not automatically equivalent to a percentage of the final formulation. A hypothetical example: 30 kg of modifier is added to 1,000 kg of base resin. The dosage is 3 phr; the final mass, ignoring losses, is 1,030 kg. The modifier represents 30 ÷ 1,030 = approximately 2.91% of the final mixture.
If the base resin in this example contains 700 kg of ABS and 300 kg of HIPS, the final composition will be approximately 67.96% ABS, 29.13% HIPS and 2.91% modifier. These proportions are only a calculation example, with no formulation recommendation. Also state whether the percentage is by mass, by volume or calculated on another basis, particularly where fillers and concentrates are present.
Visual explanation · hypothetical example
The calculation basis changes the percentage
A base of 1,000 kg of polymers receives 30 kg of modifier. The final mixture totals 1,030 kg.
- ABS
- 700 kg 67.96%
- HIPS
- 300 kg 29.13%
- Modifier
- 30 kg 2.91%
30 kg equals 3 phr relative to the polymer base and 2.91% of the final mixture. A calculation example, not a recommended recipe.
View the example's data and calculations
| Component | Mass | Approximate final fraction |
|---|---|---|
| ABS | 700 kg | 67.96% |
| HIPS | 300 kg | 29.13% |
| Modifier | 30 kg | 2.91% |
| Total | 1,030 kg | 100.00% |
Check dispersion, performance and stability
A formulation approved on its average value may fail because of variability. Compare result distributions and behaviour between batches, preserving sample identification. Where relevant, assess fracture surfaces or other evidence that helps interpret interaction between phases. Characterisation should answer the development hypothesis, rather than accumulate reports that do not change the decision.
Also observe processing: feeding, pressure, dimensional stability and scrap during conversion. An additive that improves one test may require a narrower operating window at the factory. Confirm performance after relevant storage and use conditions. Raw material approval should record limitations, because a formulation that is consistent for one part may be unsuitable for another requiring different behaviour.
Compare compatibilising, separating and redirecting
The economic calculation includes the cost of the blend, modifier, processing, tests, losses and any productivity change. Compare these expenses with the alternative of improving separation and with an application that accepts the material without modification. Do not automatically assign greater commercial value to a product with more processing stages; the buyer must recognise the performance achieved and accept its conditions.
Use revenue and cost for approved material. If a recipe increases the price per kilogram but reduces yield or generates returns, the balance may worsen. Also consider additive availability and variation in the source stream. A formulation that depends on scarce supply or an excessively narrow composition may lack robustness for an operation receiving heterogeneous materials.
Turn an approved formulation into controlled supply
Document the permitted composition, dosages, preparation, processing and control plan. Establish which changes require reassessment: waste origin, material family, filler content, modifier supplier or application. A recipe record has operational value only when the team can recognise whether the available batch falls within its conditions.
The qualification of recycled resins should connect development, production and the buyer. Keep reference samples and a procedure for investigating discrepancies. When the gain is not repeated, return to composition and process assumptions before increasing the dosage by trial and error. Compatibilisation delivers value when it solves a measurable need with technical and economic stability.
Sources and references
References accessed on 5 October 2026. The numbering in the text indicates the concepts supported by each source.
Circuvia corporate content to support project discussions. Methods, acceptance criteria and applicable requirements are defined within the scope of each operation.
