In the development of high-performance and functional polyethylene (PE) materials, modified granulation technology is a core element for expanding its applications.The PE modified three-screw granulator, based on a multi-screw synergy and modular design concept, integrates melting, mixing, dispersion, and pelletizing. It can achieve uniform plasticization and stable granulation under complex formulation conditions. Its design principle reflects a deep integration of structural innovation and process requirements.
The core design of this equipment lies in the synergistic effect of three parallel screws and a specific flow channel layout. Compared with traditional twin-screw granulators, the three-screw granulator increases the material conveying path and shear surface within the same barrel volume, allowing the PE matrix and various modifiers (such as fillers, toughening agents, flame retardants, etc.) to have more sufficient contact and exchange opportunities within the barrel. The intermeshing and asymmetrical arrangement of the screws forms a multi-directional flow field, effectively eliminating dead zones and stagnant zones, reducing the risk of thermal degradation caused by local stagnation, and improving the dispersion uniformity and interfacial bonding of the modified system.
To accommodate viscosity variations in PE under different formulations, some designs incorporate flexible or adjustable gap screw structures. This screw can undergo limited axial or radial displacement, automatically adjusting its clearance with the other two screws and the barrel when processing highly filled or high-viscosity materials. This maintains suitable shear strength and compression ratio, preventing abnormal torque or increased energy consumption due to sudden increases in resistance. This adaptive characteristic allows the equipment to maintain stable plasticizing performance even with formulation fluctuations, enhancing process tolerance.
In terms of thermodynamic design, the barrel employs a combination of zoned heating and internal screw cooling. Each heating zone has independent temperature control, allowing for fine-tuning to meet the temperature requirements of different modification stages, preventing overheating and cracking of the PE melt or insufficient plasticization. The internal screw cooling channels control shear heat generation, balancing barrel heating and internal heat dissipation to ensure a uniform and stable temperature field. This type of thermal management system is particularly important for PE modification containing heat-sensitive additives, maximizing the preservation of the functional agents' effectiveness.
The screw components feature a modular design, allowing for flexible combinations of components of different lengths and thread types based on formulation characteristics. This enables a progressive melting and mixing process, transitioning from high-pressure conveying to high-pressure shearing. The inner wall of the barrel can be hardened or treated with anti-corrosion agents to enhance wear and corrosion resistance, making it suitable for long-term processing conditions containing inorganic fillers or corrosive additives. The transmission system matches the main motor and reducer to maximum torque and power requirements, supplemented by high-precision bearings and couplings to ensure smoothness and reliability under high-speed operation.
The pelletizing stage is designed to be closely integrated with the screw melting section. Melt strands are extruded through a die, and then cooled and cut by a high-speed rotating water ring or air-cooled pelletizing device, ensuring uniform particle size and a dry surface. The overall machine layout emphasizes a compact flow path and thermal isolation, reducing heat loss and environmental pollution while improving continuous production capacity.
Overall, the design principle of the PE modified three-screw granulator revolves around multi-screw synergistic mixing, elastic adaptive adjustment, precise thermal management, and modular flexible configuration, taking into account both process adaptability and equipment durability. It provides a solid technical foundation for the stable production of high-performance modified PE materials and promotes the evolution of modified granulation equipment towards high efficiency, intelligence, and greenness.