PP (Polypropylene) luggage shells are mainly manufactured by injection molding, Injection molding can form reinforcing ribs, screw bosses and mounting positions in one piece. The finished shells feature good rigidity, rebound performance, drop resistance and bending tolerance.
Process for Injection‑Molded PP Luggage Shell
1. Raw Material Compounding & Mixing
Raw material: Mainly copolymer PP pellets. Copolymer PP is mandatory for luggage for superior impact resistance; homopolymer PP tends to crack easily.
Additives: Color masterbatch, UV stabilizer, antioxidant, toughener. Talcum powder is added in some formulas to improve rigidity.
- Mix by agitator → dehumidify & dry. PP has low moisture absorption, yet drying reduces air bubbles and flow marks.
2. Molding on Large‑Scale Injection Molding Machine
- PP pellets are melted inside the heated barrel.
- Molten material is injected into steel mold cavity under high pressure & high speed. Outer shell, inner reinforcing ribs, mounting bases for wheels / telescopic handle & lock, and logo recesses are formed integrally.
- Circulating water channels inside the mold cool and solidify parts. Cycle time: 60‑90 seconds per piece.
- Mold opens, ejector pins push out rough front‑shell and back‑shell blanks.