CRYSTAF and TREF techniques are intended to measure the Chemical Composition Distribution in Polyolefins; CRYSTAF analyzes it in the crystallization cycle and TREF in the dissolution cycle.
The analysis of complex PP-PE combinations has been shown to require both TREF and CRYSTAF to unequivocally characterize unknown samples, due to the differences in the undercooling between both resins. Such a case is the analysis of samples containing both HDPE and Ethylene-Propylene copolymer (EP) for instance. In TREF the two components will not be well resolved but CRYSTAF will be capable of getting a very good separation. An opposite case is the analysis of samples containing both HDPE and Ziegler type PP homopolymer, which will be separated better with TREF than with CRYSTAF.
Therefore, the CRYSTAF-TREF instrument is a very convenient option when needing to analyze the CCD in Polyolefins, since either CRYSTAF or TREF techniques can be performed just by changing the configuration of the equipment.