Bioplastic compounding with planetary roller extrusion
Bioplastic compounding covers a diverse and technically demanding set of materials: PLA (polylactic acid) from corn or sugarcane starch, PHA (polyhydroxyalkanoates) from bacterial fermentation, PBAT (polybutylene adipate terephthalate) as a biodegradable polymer blend component, thermoplastic starch (TPS) and starch/PE or starch/PP blends, and composites reinforced with natural fibres such as jute, hemp, and flax.
What these materials share, despite their chemical diversity, is thermal sensitivity. PLA processes in a 170–200°C window — above 200°C it undergoes hydrolytic chain scission, reducing molecular weight and mechanical properties. PHA degrades even more readily, with processing windows as narrow as 155–175°C depending on grade. Starch degrades above 170°C without adequate plasticisation. Natural fibres discolour above 190°C and lose tensile strength above 200°C.
All bioplastic processing is also moisture-sensitive. PLA and PHA absorb atmospheric moisture rapidly — PLA reaches 0.5% moisture in 4 hours at typical factory ambient conditions. At processing temperatures, moisture hydrolyses biopolymer chains, reducing molecular weight by 20–40% per processing pass if not controlled. This makes vacuum degassing during processing as important as pre-drying.
Planetary roller extruders address both thermal sensitivity and moisture management through their core geometry. The PLATEX by Takımsan generates heat conductively from the barrel rather than through viscous shear, keeping melt temperature within 3–5°C of barrel setpoints. Stage 2 vacuum degassing removes residual moisture from the melt continuously during processing. The PLATEX system overview explains the full two-stage processing architecture.
Why planetary outperforms twin-screw for bioplastics
Thermal control is the decisive factor: Co-rotating twin screw extruders generate significant viscous dissipation — typically 10–20°C above barrel setpoint at the die, depending on screw design and throughput. For conventional plastics with wide processing windows, this is manageable. For PLA at 190°C barrel setpoints, a 15°C die-face melt temperature overshoot brings the material to 205°C — above the degradation threshold. The result is molecular weight loss, yellowing, and brittleness in the extruded product.
The PLATEX planetary roller generates melt temperature within 3–5°C of barrel setpoints at equivalent throughput (estimated). For PLA processed at 185°C barrel setpoints, actual melt temperature of 188–190°C stays within the processing window. This is not achievable on co-rotating twin screws at production throughput rates.
Residence time and dead zones: Biopolymers degrade under sustained heat exposure. Any dead zone in the processing equipment — near screw roots, at transition sections, or at the die adapter — accumulates heat and degrades material. The PLATEX self-cleaning roller geometry has no stagnant zones; every material element is continuously moved and renewed. Residence time distribution on the PLATEX is narrow, with no leading or lagging tail of material that has received significantly more or less thermal history than the mean.
Moisture removal: The planetary roller’s thin film geometry maximises surface area per unit volume of melt, which is the rate-limiting factor for moisture evaporation into the vacuum headspace. At equivalent throughput and vacuum conditions, the PLATEX removes more moisture from the melt per pass than a twin screw, where the melt depth in the vacuum zone is greater.
Natural fibre handling: At natural fibre loadings of 20–40% by weight, the PLATEX’s rolling contact applies lower specific shear stress to fibres than twin screw flight gaps. This preserves fibre length and fibre-matrix interface quality, which directly determines composite stiffness and impact resistance in the downstream part.
See PLATEX vs twin-screw for a full technical comparison.
Recommended PLATEX models
For bioplastic formulation R&D, compound qualification, and small-volume production (pilot scale), the PLATEX 80 lab extruder (max 45 kg/hr) is the first specification. It allows testing of temperature windows, chain extender loading, and pre-drying protocols before committing to a production run. The PLATEX 80 is one of only two commercially available lab-scale planetary extruders worldwide, as identified by academic reviewers Formela and Eyigöz.
For speciality bioplastic production at 100–200 kg/hr — custom PLA blends, PHA medical-grade compound, natural fibre composite for automotive — the PLATEX 100 (45 kW, PR 100) is the correct specification. Batch sizes of 200–500 kg stay manageable and formulation changeover completes within a shift.
For scale-up to production volumes of 250–700 kg/hr, the PLATEX 155 (55 kW) is appropriate. PLA melt viscosity is lower than rigid PVC, so the PLATEX 155 typically operates at 50–70% of its motor rating on unfilled PLA compound, with margin available for filled or high-MW grades.
Run your formulation in our lab
Bioplastic formulation development benefits most from lab-scale validation before any production commitment. Send a 3–5 kg sample (pre-dried to specification) to Takımsan’s İstanbul facility. Our team runs it on the PLATEX 80 lab extruder and report melt temperature profile, MFI of output pellets vs input resin, vacuum degassing load, and a qualitative assessment of discolouration, odour, and pellet quality. Contact Takımsan to arrange a sample run.
