This is the most common problem when you process with CaCO3 FILLER MASTERBATCH, there are many reasons that could lead to this problem and the main reasons are :
The Melt Flowing Index of CaCO3 FILLER MASTERBATCH is extremely lower than the PP Resin, then FILLER can’t melt totally when you process.
The PP content in CaCO3 FILLER MASTERBATCH is low that couldn’t cover all CALCIUM CARBONATE molecules. It leads to the unmelt CALCIUM CARBONATE come out which will make the film be broken.