Meaning
Analytical separation techniques divide complex polyethylene or polypropylene resins into distinct groups based on molecular weight and co-monomer distribution. This method reveals the underlying structure of the polymer beyond simple density or melt index values. Through polyolefin fractionation, researchers can understand how the distribution of chains affects the mechanical properties of the finished part.
Column Resolution
Solvent gradients or temperature changes are used to elute different portions of the sample from a chromatography column. High resolution allows for the clear separation of the low molecular weight wax from the high molecular weight structural chains. The polyolefin fractionation data identifies whether a resin has a narrow or broad distribution.
Property Determination
Crystalline content and branch frequency vary across the different fractions of the polymer. Fractions that contain more co-monomer are usually less crystalline and contribute to the impact resistance of the material. By performing polyolefin fractionation, a supplier can tailor the resin for specific applications like film extrusion or blow moulding.
Material Consistency
Batch to batch variation in the distribution of molecular weights can lead to processing issues like melt fracture or uneven shrinkage. If the ratio of short to long chains shifts, the viscosity of the melt will change. Using polyolefin fractionation as a quality control step ensures that every shipment of resin performs the same way in the injection moulding machine.
This level of detail is particularly useful when switching between different resin suppliers or when trying to match the performance of a competitor material.
