Soft PVC compounding with planetary roller extrusion
Soft PVC — polyvinyl chloride plasticised to 30–100 phr with phthalate or non-phthalate plasticisers — is the material of choice for cable insulation and sheathing, medical-grade tubing, automotive interior trim, flooring and artificial leather, and speciality film. It is one of the most formulation-diverse thermoplastics in production: the same base PVC resin can yield compound hardness from Shore A 60 to Shore D 50 depending on plasticiser type and loading.
Processing soft PVC on conventional equipment presents a specific challenge: ensuring complete, homogeneous plasticiser absorption without generating localised temperature excursions that cause early stabiliser depletion or discolouration. Internal batch mixers achieve good plasticiser absorption but are inherently discontinuous, with each batch representing a separate quality event. Twin screw extruders are continuous but generate localised shear heating that can cause visible yellowing in transparent or light-coloured grades.
The PLATEX planetary roller extruder processes soft PVC through a film-forming mechanism that distributes plasticiser across the entire melt film surface simultaneously. Because each film element is 0.5–2 mm thick and continuously renewed, plasticiser absorption is complete without relying on extended shear. The result is a homogeneous compound at lower melt temperature than twin screw processing — typically 10–15°C lower at equivalent throughput (estimated) — with the consistency advantage of continuous processing over batch mixing.
This matters practically for cable compound producers running 24-hour production and needing stable dielectric properties across all shifts, for flooring compound producers where surface finish consistency determines product grade, and for medical compound producers where thermal processing history is a regulatory documentation requirement. For a full comparison of processing principles, see PLATEX vs twin-screw.
Why planetary outperforms twin-screw for soft PVC
Plasticiser absorption: In soft PVC, the plasticiser must be fully absorbed into the PVC matrix — a process that requires both sufficient temperature and sufficient contact time. Twin screw extruders achieve this through high shear, which generates localised heating. The PLATEX achieves it through prolonged, gentle film-forming contact across the helical roller geometry. At 50 phr DOTP, the PLATEX typically achieves complete absorption (>95% by THF extraction) with barrel temperatures 5–10°C lower than a comparable twin screw, because the extended film-forming contact replaces high-shear energy input.
Temperature uniformity: Soft PVC transparent grades — used in medical tubing and packaging film — are particularly sensitive to localised overheating. A single temperature excursion above 185°C is visible as yellowing or haze in a transparent compound. The planetary roller’s thin film geometry distributes thermal input uniformly; there are no high-shear zones that can spike melt temperature locally. Transparent grade production on PLATEX reliably achieves colour b* values below +2 at 600 kg/hr.
Plasticiser vapour management: At processing temperatures, plasticiser with boiling points below 250°C will begin to volatilise. Stage 2 vacuum degassing in the PLATEX captures plasticiser vapour before the discharge section, preventing vapour from entering the gearbox and reducing atmospheric exposure in the production area.
Output consistency: Batch mixers produce compound quality that varies between batches — mixer temperature, mixing time, and charge weight all contribute to batch-to-batch variability. The PLATEX’s continuous film-forming process produces compound with significantly narrower within-run and run-to-run variability, which reduces the proportion of off-spec material that must be re-processed.
Energy comparison: At 500 kg/hr on a 50 phr DOTP soft PVC compound, total PLATEX 155 power draw is approximately 65–75 kW. An equivalent internal mixer/extruder line at the same output typically draws 80–100 kW total. Over a 6,000-hour year, approximately €10,000–15,000 estimated difference at €0.10/kWh.
Recommended PLATEX models
For speciality soft PVC compounding — medical-grade tubing, transparent film, custom colour work — the PLATEX 100 (100–200 kg/hr, 45 kW) is the right specification. Batch sizes stay manageable, colour changes complete within a shift, and the footprint (280 × 260 × 150 cm) fits standard production bays.
For cable insulation compound and flooring compound at industrial scale, the PLATEX 155 (450–800 kg/hr, 55 kW) and PLATEX 165 (600–1,100 kg/hr, 75 kW) are the standard production models. At 50 phr DOTP loading, both operate well within their motor rating, with torque well below the operating ceiling.
For formulation development of new soft PVC grades — new plasticiser alternatives, REACH-compliant stabiliser systems, or medical-grade qualification — the PLATEX 80 lab extruder (max 45 kg/hr) is the correct starting point.
Run your formulation in our lab
Send a 5–10 kg sample of your soft PVC premix (PVC + plasticiser cold blend or warm blend) to Takımsan’s İstanbul facility. Our team runs it on the PLATEX 80 lab extruder and report torque, melt temperature, plasticiser absorption (MEK extraction), and pellet quality. For medical-grade trials, a clean-condition barrel is confirmed before each run. Contact Takımsan to arrange a sample run.
