Can Different Plastics Be Granulated Together?
They Can Be Granulated — But Think Through the Consequences
Feeding different plastics mixed together into a granulator typically does not damage the machine, and the granulation process itself can complete. The issue is not "can it be granulated" but "where can the granulated output be used?" Mixed granulation severely degrades regrind quality, greatly narrows application range, and dramatically reduces recovery value.
Whether you can accept these consequences determines whether you should mix different plastics for granulation.
Three Main Problems with Mixed Granulation
Problem 1: Incompatible material properties — poor regrind quality
Different plastics have different chemical structures. Mixed together and melted, they do not form a uniform blend — instead they form a layered or phase-separated structure. This makes the mixed regrind's physical properties highly unstable — strength, toughness, and elongation are all lower than single-material regrind; molding produces layering, cracking, or surface defects.
The most common mixing problem is PP and PE together. Although both are polyolefins and look similar, their compatibility after melting is poor — mixed regrind tends to show stripe-pattern phase separation during molding, with unstable mechanical properties. Even worse is mixing completely different plastic families — PE and PET, or PP and ABS — with even poorer compatibility, producing mixed regrind with almost no usable value, suitable only for the lowest-grade filler material.
Problem 2: Different melting points — difficult pelletizing
Different plastics have very different melting temperatures: PP melts at approximately 160–170°C; PC at 230–250°C; PET at 250–260°C. When mixed material enters a pelletizer, any single temperature setting leaves some materials still not fully melted (solid particles appear in the regrind) or others already overheating and degrading (regrind becomes brittle and discolored). This makes setting appropriate processing parameters for mixed material nearly impossible — output quality is poor and inconsistent.
Problem 3: Low market price — large recovery value loss
Pure-material regrind has an established market — buyers know exactly what the material is and what its properties are, willing to pay a fair price. Mixed-material regrind has uncertain composition; buyers don't know what they can make with it or whether properties will be stable. Purchase willingness is low; prices may be only one-third to one-half of pure-material regrind.
When Mixed Granulation Is Acceptable
Not all mixed granulation is a bad idea. Some situations make it a reasonable choice:
Downstream use genuinely does not care about material type: if the granulated output will be used for filler material or very low-requirement industrial products (certain construction accessories, road base material), with very low material purity requirements, mixed regrind quality is already adequate.
The mixed plastics are from similar families: mixing plastics of the same family (such as polyolefin family PP and PE) has better compatibility than completely different plastic families. Quality drop is relatively limited, and the regrind may still be usable for some lower-requirement applications.
Too little of one material type to make separate processing economical: if one plastic type appears in very small quantities, the value of separate granulation and sale does not justify the effort — mixing it with other waste is pragmatic, though recovery value is sacrificed.
Producing recycled plastic-wood composite (WPC): mixed plastic waste has a special application outlet — plastic-wood composite materials that inherently allow mixed plastics with relatively low material purity requirements.
When Plastics Must Be Granulated Separately
Waste is going back into the production process: mixing different plastics into re-feed regrind causes product defects — sink marks, delamination, strength reduction. Even small amounts of different materials can cause visible defects in quality-sensitive products.
Waste will be sold to specific buyers: most regrind buyers specify material type and do not accept mixed materials. If your waste has established buyers, mixing almost certainly costs you that sales channel.
Waste contains PVC: mixing PVC with other plastics for granulation is the most critical situation to avoid. PVC contains chlorine — at pelletizer temperatures it may release hydrogen chloride gas, corroding the machine. Even without pelletizing, PVC mixed into PE or PP regrind may release harmful gas during the high temperatures of molding, seriously affecting regrind safety and application range.
Waste is tracked for ESG reporting: mixed-material granulation makes material traceability and recycled content calculation difficult — not favorable for clear data presentation in ESG reports.
Practical Classification Management Recommendations
To avoid mixing, the most important step is classifying waste at the point of generation — not trying to sort it before feeding.
Set up separate collection bins at the production line: one bin per material type, clearly labeled; operators classify waste directly into the correct bin as it is generated — no need to sort later.
Collect color-change purge separately: color-change purge contains mixed and impure material — cannot be mixed with pure-material waste. Collect separately; evaluate and decide on disposition independently.
Collect materials of unknown type separately: waste of uncertain material type should not be added to known-material bins. Confirm the type first, then classify. A rough field identification can be done with a lighter (burn test) — observe burning characteristics to distinguish natural fiber from synthetic fiber, or different plastic families — but be careful with safety and ventilation.
Related articles: How to Granulate General Plastic Waste (PP, PE, ABS, and Other Common Plastics); How to Plan Scrap Recovery in an Injection Molding Plant — practical recommendations for waste classification management; Plastic Regrind vs. Virgin Resin — how mixing affects regrind quality and market price.