Foaming of Novel Linear Polyethylene with Enhanced Melt Elasticity
Masayuki Yamaguchi
TOSOH Corporation
Japan

Keywords: Foam, elongational viscosity, polyethylene

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Rheological properties and foam processability have been studied for novel linear low-density polyethylene (LLDPE) having considerably stronger melt elasticity than a conventional LLDPE.
It was found that the novel LLDPE with no long-chain branch exhibits marked strain-hardening in elongational viscosity as similar to that of a branched LDPE, whereas the growth curves of elongational viscosity for a conventional LLDPE with the same level of steady-state shear viscosity coincides with 3 times of the shear viscosity at a low strain rate asymptote. Further, the novel LLDPE also exhibits significant extrudate swell due to the pronounced primary normal stress difference.
Moreover, the foam processability was also evaluated as compared with the conventional LLDPE. The enhanced strain-hardening in elongational viscosity prevents local deformation during foaming, and results in uniform deformation. Consequently, the foams obtained from the novel LLDPE exhibit high expansion ratio and homogeneous distribution of the cell-size.