Direct Answer: The carrier resin of a masterbatch must be rheologically and chemically compatible with the base conversion polymer. Using an incompatible carrier can cause phase separation, surface delamination, poor weld line strength, and reduced impact resistance.
1. Specific vs. Universal Carriers
While "universal" masterbatches utilize low-melting polymers (like EVA) to facilitate dispersion across diverse plastics, premium engineering applications require specific polymer-matched carriers (e.g., HDPE masterbatch for HDPE pipes, PP masterbatch for PP homopolymer woven sacks).
2. Melt Flow Index (MFI) Alignment
The carrier polymer must possess a Melt Flow Index slightly higher (lower viscosity) than the host resin at conversion temperature. This ensures that the masterbatch melts rapidly, allowing the concentrated pigments and additives to distribute homogeneously before entering the shaping die or mould cavity.