BRANCHING MEASUREMENT BY ANALYTICAL TREE - A FULLY QUANTITATIVE TECHNIQUE

Conversion of analytical TREF data to accurate branching distributions of polyethylene requires a calibration of branching frequency as a fu nction of elution temperature. It has been found that the elution temp erature of a semicrystalline polymer such as polyethylene depends on m olecular weight, branch content, branch length, and branch clustering. It stands to reason that every polymer will have its own unique relat ion of branch frequency and elution temperature. Ideally, the polymer would be fractionated by a preparative TREF technique and the fraction s analyzed by NMR or IR to determine branch frequency with respect to elution temperature. This method is tedious and time-consuming. An alt ernative method is described here to determine the relation between br anch frequency and TREF elution temperature and to generate a calibrat ion from analytical TREF data only. A two-detector system is used to s imultaneously measure both concentration and branching frequency as a function of elution temperature. Each polymer is analyzed using analyt ical TREF data alone, eliminating the need for preparative TREF fracti onation and NMR analysis of the fractions. (C) 1994 John Wiley & Sons, Inc.