MFI/MI/MFR de Plástico (English- Español)

In general if MI value is greater, it represents a smaller plastic viscosity and smaller molecules. For the actual use, MI values can be used as a standard to inspect the quality of plastic pellets (resin) ; MI can also be used as a reference to check whether it is mixed with secondary materials (re-grinding); also is used to explain the degradation (degrating) phenomenon before and after plastic injection.

 

We can imagine that plastic is made up with a long string of entangled molecular chain; when the chain is longer, the larger extent of which it intertwines and becomes more solid, thus the plastic melt flow rate will be the slower. When plastic is heated after going through the injection molding machine, the helical rod of the machine will break its molecular chain, so the MI would be higher, usually about 20~30% higher than pre-molding (depending on molding conditions), which also explains why generally the MI of dyed plastic pellets is higher than undyed plastic pellets.