Compounding
Compounding is all about mixing and blending polymers and additives when they're in a molten state to make plastic formulations. These blends are then dosed automatically with fixed setpoints, usually through feeders or hoppers.
Extrusion is the usual way to do it. The hopper feeds the start of the screw, which gradually moves the resins towards the die. The screw itself is confined in a barrel that has different zones that can be heated according to the properties of the resins.
The most common compounders in the plastic industry are co-kneaders and twin screws (co- and counter rotating) as well as internal mixers.
ThermoFisher™ HAAKE™ miniCTW
The ThermoFisher™ HAAKE™ miniCTW (or mini-compounder) is very appropriate to compound and extrude small quantities. This conical double-screw compounder enables us to test a large spectrum of different materials and to screen a large number of processing conditions or product combinations in an affordable and quick manner. Ideal for tests with nanomaterials or engineered biopolymers.
The optional Force Feeder system enables a continuous material throughput. This screw-feeder is air-cooled to prevent clogging.
In addition to a continuous extrusion mode, the minicompounder allows a backflow mode through a recycle configuration, resulting in a optimised blend. The use of pellets involves that the material dosing is approached from a statistic distribution. However, this is solved by using powders or by partly mixing the blends beforehand.
Technical Specifications
The co-rotating and counter-rotating configurations guarantee an optimised blending. The heat regulation is limited to one single temperature for the entire barrel and cannot be divided into different zones.
The mini-compounder is computer-assisted enabling the online follow-up and graphic display (in function of time) of temperature, screw speed and couple. It is also possible to add an event at a certain point of time.
- Temperature: between ambient temperature and 300°C
- Heat output: 800W.
- Screw speed: between 10 to 360 rpm
- Max. couple: 5Nm.
While many parameters—such as temperature, screw speed, and torque—can be preset, scaling up the process remains complex. Nevertheless, with optimized processing conditions, it is possible to achieve blends exhibiting exceptionally fine dispersion
Leistritz ZSK27 Twin Screw Compounder – Precision Compounding for Advanced Materials
This pilot-scale twin-screw compounder can be used for formulation and process development, scale-up to production scale and small batch production (24-hour continuous operation).
The Leistritz ZSK27 is a high performance co-rotating twin screw compounder designed for laboratory and pilot scale applications requiring flexibility, consistency and process accuracy.
With a screw diameter of 27 mm and an L/D ratio of up to 44:1, the ZSK27 is ideal for the development and optimisation of complex formulations, from thermoplastics and filled compounds to biopolymers and reactive systems.
Key features and technical specifications
- Screw Diameter: 27 mm
- L/D Ratio: Up to 44:1
- Maximum Torque: Approx. 88 Nm (per shaft)
- Maximum Screw Speed: Up to 1,200 rpm
- Throughput Capacity: Typically 5–50 kg/h (material dependent)
- Modular Barrel Design: For flexible process setups and easy reconfiguration
- Precise Temperature Control: Zone-specific heating and cooling
Designed for scalable experimentation and small-scale production, the ZSK27 delivers exceptional mixing, dispersion, and devolatilization performance. Its user-friendly control interface and robust construction make it a reliable choice for R&D labs, universities, and specialized production lines across industries.
Underwater pelletizing for thermoplastic compounds
TPUTM Small lab pelletizing system for lab-scale developments and small-scale pellet production, including an underwater pelletizer, a tempered water system, and pellet dryer.
The pelletizer is connected to the twin-screw coumpounder and operates in a closed loop. The perfectly round pellets are transported by the process water of the cutting chambre to the centrifugal dryer. Because the entire process is taking place without any contact with the ambient air, there is no gas and dust emissions and no risk of contaminating the product.
The process water remains within the closed loop of tempered water system where it is reused for subsequent production runs.
Features
Compared to the “dry-cut pelletizing” systems the underwater pelletizer is less subject to wear and offers more flexibility during the production of thermoplastic compounds. The granules are perfectly spherical and there is no dust emission during the cutting process.
The pelletizing system interfaces with the twin screw compounder. The process is performed in a closed loop system. The pelletized product is conveyed by the process water from the cutting chamber into the centrifugal dryer. During the process, the pelletized product has no contact with the ambient air and there is no risk of gas, dust emission or contamination of the product.
The process water remains in the closed loop tempered water system, another advantage which contributes to the environment.
The Gala’s LPU™ Laboratory Pelletizing System is a small lab pelletizing system, designed for pellet rates up to 15 kg/h. The LPU™ Laboratory Pelletizing System includes an underwater pelletizer, a tempered water system, and a new and simple pellet dryer — all mounted on a single chassis with swivel casters.
Benefits
- Easy cleaning
- Simple & easy operation
- Lightweight, portable
- No movement of pellets against the dryer components
- Long life span of all parts coming into contact with the pellets
- Extremely gentle pellet-handling ensuring high product quality and minimale dust levels
- Reduced energy consumption: no additional heating required
- Wide variety of polymers: including high additive content, high viscosity to very low viscosity materials
Video © Gala
The Gala’s LPU™ Laboratory Pelletizing System is a small lab pelletizing system, designed for pellet rates up to 15 kg/h. The LPU™ Laboratory Pelletizing System includes an underwater pelletizer, a tempered water system, and a new and simple pellet dryer — all mounted on a single chassis with swivel casters.
Acknowledgements
The investment in the underwater pelletizer was made in the framework of the programme "Circularity in & with New Materials" aiming at optimizing the use of recyclates to promote the circular economy.
