1. Raw Material Optimization
Raw material condition is the foundation of perfect board surfaces. Most surface defects stem from impure materials and unreasonable formulas.
- Control material purity: Screen new and recycled PP materials strictly to remove impurities and dust, avoiding surface pits and hard spots after extrusion.
- Optimize additive ratio: Add proper smooth agents, lubricants and antistatic agents to improve melt fluidity, reduce mold adhesion and boost surface gloss.
- Avoid mixed materials: Do not mix PP materials with different melt indices, which causes uneven fluidity and surface streaks.
2. Extrusion Parameter Adjustment
Extrusion temperature and speed directly affect PP melting status, which is critical for smooth surfaces. Improper parameters easily cause bubbles, rough surfaces and wavy lines.
|
Process Section |
Parameter Adjustment Tips |
Improvement Effect |
|---|---|---|
|
Barrel Temperature |
Stable temperature at 190-210℃ without sharp fluctuations |
Ensure uniform melting and eliminate rough granular surfaces |
|
Die Head Temperature |
Properly raise temperature to optimize melt fluidity |
Smooth surfaces and reduce extrusion streaks |
|
Screw Speed |
Match feeding speed to avoid excessive shearing |
Prevent material overheating and surface fogging |
3. Mold Maintenance & Calibration
Mold condition directly determines board surface finish. Clean and calibrated molds are essential for high-quality surfaces.
- Regular mold cleaning: Remove residual materials and carbon deposits to avoid continuous surface scratches.
- Mold polishing maintenance: Keep mold surfaces polished and smooth to prevent dull, rough boards.
- Check mold gap: Maintain uniform gap to avoid uneven melt outflow and wavy deformation.
4. Cooling & Traction Control
Unstable cooling and traction are common causes of surface warping and poor flatness.
- Gradual uniform cooling: Use segmented water cooling to avoid rapid cooling, preventing internal stress and micro-cracks.
- Stable traction speed: Keep constant speed to avoid tension fluctuation and surface wrinkles.
5. Solutions for Common Surface Defects
Here are targeted solutions for frequent surface defects to improve production yield:
- Surface bubbles: Caused by moist materials or overheating. Dry materials thoroughly and lower extrusion temperature slightly.
- Streaks & scratches: Caused by dirty molds or foreign particles. Clean molds and inspect friction parts regularly.
- Dull surface: Caused by insufficient lubrication or low die temperature. Increase lubricant and optimize die temperature.
Conclusion
PP hollow board surface quality depends on raw materials, extrusion parameters, mold maintenance and cooling processes. Optimizing every production link can effectively eliminate common defects, improve surface finish, and deliver high-performance hollow boards for global packaging, construction and logistics applications.
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