MFR = melt flow rate
Before: melt flow index (MFI)

The types of polyethylene available on the market may differ considerably in their flowability in the thermoplastic range. These differences influence the weldability of different join partners in that an insufficient mixing of the interfaces may occur due to the different mobility of the molecular chains (at the same welding temperature). In order to get this problem under control, the polyethylenes have been classified into categories according to their flowability.

A prerequisite for optimal welding is that the melting behaviour of the two join partners is as similar as possible.

In general, MFR-groups of the same kind can be welded and in many cases also neighbouring groups.