The production of PS (polystyrene) transparent sheets requires high stability and precision from extrusion equipment. As a core component of the extrusion system, the melt pump can enhance product quality by maintaining stable pressure and flow rates and eliminating fluctuations. The following is a technical analysis and recommended solution for melt gear pumps in PS transparent sheet extrusion processes:
1. PS Material Properties and Extrusion Process Requirements
Material Properties
PS is an amorphous polymer with a light transmission rate of 88%-92%, but it presents the following extrusion challenges:
Thermal Sensitivity: Poor heat resistance (heat deflection temperature 70-90°C), prone to degradation at high temperatures;
Shear sensitivity: Viscosity drops sharply at high shear rates, leading to melt fracture;
Dimensional stability: Strict control of extrusion pressure fluctuations is required to prevent reductions in light transmittance or surface defects.
Process Requirements
PS transparent sheet extrusion must meet the following requirements:
Low-temperature extrusion: Reduce thermal degradation and maintain light transmittance;
Stable pressure: Eliminate screw pulsations to ensure uniform sheet thickness (CV value <3%);
Low shear design: Avoid surface flow marks caused by melt rupture.
2. The Core Role of Melt Pumps in PS Transparent Sheet Extrusion
Pressure and Flow Stability
Melt pumps create a sealed chamber through gear meshing, controlling extruder output pressure fluctuations within ±1% and flow fluctuations ≤±0.5%, significantly improving sheet thickness uniformity.
Case study: In a BOPP film production line, installing a melt pump reduced thickness deviation CV value from 5% to 2.5% and improved light transmission by 2%-3%.
Low-temperature extrusion and energy savings
The melt pump transfers the extruder's pressure-reduction function to the pump body, enabling the extruder to operate at low pressure and low temperature (temperature reduced by 20-30°C), thereby reducing the risk of PS degradation.
Data: After installing a melt pump on a single-screw extruder, energy consumption is reduced by 10%-15%, and screw lifespan is extended by 20%-30%.
Shear Homogenization and Mixing Optimization
The high-shear gear design improves PS melt uniformity, eliminates unmelted particles, and enhances surface smoothness.
Application: In PS/HIPS blending modification, the shear effect of the melt pump enables more uniform dispersion of rubber particles, improving impact resistance by 15%-20%.
3. Key Considerations for Selecting a Melt Pump for PS Transparent Sheet Extrusion
Temperature and Pressure Adaptability
Operating Temperature: The processing temperature range for PS is 150-250°C, requiring a melt pump with a temperature resistance of ≤350°C (e.g., ZB-B series);
Pressure Range: Inlet pressure 0-30 MPa, outlet pressure 0-40 MPa, suitable for high backpressure conditions.
Viscosity and Flow Rate Matching
PS melt viscosity range: 1,000-10,000 Pa·s. A melt pump with flow rate accuracy of ±0.1 cm³/rev is required;
Recommended model: Displacement range of 0.05CC-30000CC, suitable for different production capacity requirements.
Material and sealing design
Gear material: High-strength alloy steel (e.g., 38CrMoAlA) treated with nitriding, improving wear resistance by 50%;
Sealing system: Spiral seal or double-ended mechanical seal to prevent PS melt leakage and contamination.
4.Recommended Solution
For PS transparent sheet extrusion, we recommend using the ZB-B series melt pump, whose core advantages include:
Optimized flow channel design: avoids dead corners, reduces material residue, and prevents PS thermal degradation;
Improved gear parameters: Output pressure pulsation rate <0.5%, suitable for precision extrusion;
High-temperature adaptability: Operating temperature ≤400°C, cleaning temperature ≤450°C, meeting PS processing requirements.
Conclusion: The melt pump achieves stable pressure, reduced shear, and low-temperature extrusion, significantly improving the light transmission rate, dimensional accuracy, and surface quality of PS translucent sheets, making it a key piece of equipment for upgrading PS extrusion processes.
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