Long and short chain branching frequency in low density polyethylene (LDPE)

Abstract

Five different laboratories have collaborated in a researct programme on determination of the branching frequency in a LDPE sample. Size exclusion chromatography (SEC), SEC-on-line viscosity (OLV) measurements, DSC-, NMR-, viscosity measurements, as well as SEC-online low angle laser light scattering (LALLS) measurements and off-line LALLS measurements, were performed on both the whole sample and on fractions. The fractions were obtained by temperature rising elution fractionation (TREF) and by liquid-liquid phase separation (L-L), respectively. Different long chain branching (LCB)-parameters can be derived. Their differences were explained and some of them were used in gation. Also, different 8-values in the expression 9ü=g were used and discussed. AB-value of 0.9 was obtained for the global sample. The conclusion o f the fractionation work on the LDPE was that TREF fractionates according to short chain branching (SCB) and that L-L fractionates according to LCB. © 1988 IUPAC