Knowledge
May 26, 2026
By Bepa Zhu
PP Raffia Grade Selection: MFR & Isotacticity
Two resin properties dominate raffia grade choice: melt flow rate (MFR) and isotacticity. MFR is a proxy for molecular weight, while isotacticity describes how regularly the propylene units are arranged along the chain.
A lower MFR means longer polymer chains and, generally, higher tape strength after drawing, but it also raises melt viscosity and extruder load. A higher MFR processes more easily yet yields less robust tape, so the choice is a balance rather than a single optimum.
Isotacticity drives crystallinity. A more isotactic homopolymer crystallizes more readily, giving better stiffness, heat resistance and tensile properties in the finished woven or rope product. It also influences shrinkage and dimensional stability under load.
