To avoid bubbles and delamination in the PVC waterstop extrusion molding process, the following measures should be implemented:
Material Preparation and Handling
Thorough Drying: Ensure PVC resin and additives are fully dried to eliminate moisture, a primary cause of bubbles. Use pre-drying equipment at 80–120°C for 2–4 hours to reduce moisture content below 0.1%.
Uniform Mixing: Use high-speed mixers to evenly disperse additives (e.g., stabilizers, plasticizers) and avoid agglomeration, which can lead to delamination .
Process Parameter Optimization
Temperature Control: Maintain consistent barrel and die temperatures (typically 160–190°C) to prevent overheating (causing thermal decomposition bubbles) or insufficient melting (leading to delamination).
Screw Speed and Back Pressure: Adjust screw rotation speed (40–60 rpm) and back pressure (0.5–1.5 MPa) to ensure proper塑化 and eliminate trapped air.Vacuum Degassing: Apply vacuum systems (≥0.08 MPa) during extrusion to remove volatiles and air from the melt.
Equipment and Mold Design
Screw and Barrel Maintenance: Regularly clean wear-prone parts (e.g., screw flights, barrel liners) to prevent material stagnation and degradation.
Mold Venting: Design molds with adequate venting channels or vacuum-assisted systems to release trapped gases.
Uniform Flow Channels: Optimize die geometry to ensure balanced material flow, avoiding shear-induced delamination .
Post-Extrusion Management
Cooling Rate Control: Use gradual cooling (e.g., water baths at 20–40°C) to minimize internal stress and layer separation.
Quality Monitoring: Implement real-time thickness gauges and visual inspection systems to detect bubbles or delamination early .
For specialized applications, consider using tailored PVC waterstop profiles such as Internal Expansion Joint PVC Waterstop, Internal Construction Joint PVC Waterstop, External Construction Joint PVC Waterstop, and External Expansion Joint PVC Waterstop to accommodate structural movements while maintaining integrity.
