The morphology of blends of linear and branched polyethylenes
- Oak Ridge National Labs., TN (United States)
- Florida State Univ., Tallahassee, FL (United States)
The state of mixing in blends of high density (HD), low density (LD) and linear low density (LLD) polyethylenes (PE) in the melt and solid states has been examined by small-angle x-ray and neutron scattering (SAXS and SANS). In the melt, SANS results indicate that HDPE/LDPE mixtures (with 1-2 branches/100 C) form a single phase. HDPE/LLDPE blends are also homogeneous when the branch content is low, but phase separate as the branching increases. In the solid state, after slow-cooling from the melt, the HDPE/LDPE system segregates into domains {approximately}10{sup 2} in size. For high concentrations of linear polymer ({phi} {ge} 0.5), there are separate stacks of HDPE and LDPE lamellae, and the measured SANS cross section agrees closely with the theoretical calculation based on the assumption of complete phase separation of the components. For predominantly branched blends ({phi} < 0.5), the phase segregation is less complete, and the components are separated within the same lamellar stack. Moreover, the phases no longer consist of the pure components, and the HDPE lamellae contain up to 15% LDPE. The segregation of components in the solid state is a consequence of crystallization mechanisms and the blend morphology is a strong function of the cooling rate. Rapid quenching to -78{degrees}C produces only one lamellar stack and these blends show extensive cocrystallization. Samples quenched less rapidly (e.g., into water at 23{degrees}C) show a similar structure to slowly cooled samples. The solid state morphology also depends on the type of branching and differences between HDPE/LDPE and HDPE/LLDPE blends will be reviewed.
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 535330
- Report Number(s):
- CONF-951022-; TRN: 97:004030-0010
- Resource Relation:
- Conference: Intersociety polymer conference: creation, utilization and recycling of multiphase polymer systems, Baltimore, MD (United States), 7-10 Oct 1995; Other Information: PBD: 1995; Related Information: Is Part Of Intersociety polymer conference - creation, utilization, and recycling of multiphase polymer systems; PB: 65 p.
- Country of Publication:
- United States
- Language:
- English
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