Precautions for PPS Plastic Injection Molding

PPS is a high-temperature engineering plastic with high rigidity, low water absorption, and narrow processing window. It requires strict control of drying, temperature, injection, and cooling to avoid degradation, bubbles, or deformation.

Material Drying

Drying requirements: Use dehumidifying dryers at 120–140℃ for 3–4 hours (trace moisture accelerates degradation).Storage: Seal raw materials in a dry, cool area; use dried material within 2 hours (re-dry if exposed to air).

Barrel Temperature Control

Recommended temperatures: Rear 260–280℃, Middle 290–310℃, Front 300–320℃, Nozzle 300–310℃.Critical notes: Avoid overheating (causes degradation/yellowing) or underheating (poor flow/short shots). Purge with PP/PE before shutdown to prevent carbonization.

Mold Temperature Requirements

Standard parts: 120–150℃ (ensures crystallization and dimensional stability).High-precision parts: 150–180℃ (improves rigidity and surface quality).Key rule: Use a mold temperature controller (avoid natural cooling for inconsistent temperatures).

Injection Pressure & Speed

Pressure: Moderate-to-high injection pressure (avoid excessive pressure to reduce internal stress/flash).Speed: Medium-to-high speed (stable filling, no shear overheating).Holding pressure: Minimal pressure to prevent sink marks (high pressure increases warpage).Back pressure: Low (reduce shear heat and material degradation).

Mold & Venting

Venting: Add 0.015–0.02mm deep vents at weld lines/flow ends (prevent burning/trapping gas).Mold steel: Use H13/SKD61/S136 for glass-filled PPS (wear/corrosion-resistant, nitride-treated for longevity).

Cooling & Ejection

Cooling: Sufficient cooling time (prevents warpage/cracking from rapid crystallization).Ejection: Balanced ejector layout (avoid local stress); slow ejection speed (prevent chipping of brittle PPS).Draft angles: Increase angles on deep cavities/ribs (prevent sticking/scratching).

Post-Treatment & Quality Control

Annealing: 150–180℃ for 1–2 hours (eliminates internal stress, stabilizes dimensions).Inspection: Reduce temperature for yellowing/bubbles; increase pressure for short shots; lower pressure for flash/warpage.

Safety & Equipment Maintenance

Safety: Ensure good ventilation (PPS releases corrosive gases at high temperatures).Maintenance: Regularly inspect/wear parts (screws, barrels, molds) for glass-filled PPS wear.