TIME-RESOLVED SMALL-ANGLE X-RAY-SCATTERING OF A HIGH-DENSITY POLYETHYLENE LOW-DENSITY POLYETHYLENE BLEND

The semicrystalline morphology of a 50/50 blend of high density polyethylene/low density polyethylene (HDPE/LDPE) was studied by time-resolved small-angle X-ray scattering (SAXS) using the State University of New York (SUNY) Beamline at the National Synchrotron Light Source (NSLS). The HDPE/LDPE blend, which was cooled slowly at a cooling rate of 0.3 °C/min, showed an interfibrillar scale separation within the spherulites that contained both the HDPE and the LDPE component. On the other hand, the same polymer blend, which was cooled rapidly at a cooling rate of 110 °C/min, appeared to show separation of HDPE and LDPE on an interlamellar scale. When the blend was quickly cooled to two successive temperatures, the scattering profiles were similar in nature to those obtained from the same sample that was directly quenched. The two-step rapid cooling represented quenching (1) from ~125 °C, which was above the HDPE crystallization temperature, to 110 °C, which was lower than the HDPE crystallization temperature but higher than the LDPE crystallization temperature, and (2) from 110 to 100 °C, which was below the LDPE crystallization temperature, while the direct rapid cooling was from 135 to 65 °C. © 1990, American Chemical Society. All rights reserved.