Polyolefins dominate
the market for commodity plastics due to their
low cost and suitable properties, but polyolefins are rarely used
in 3D printing due to issues with deformation of the printed structure
during crystallization from the large volume change. Here, we demonstrate
that filaments containing approximately 50% of either high density
or low density polyethylene (HDPE/LDPE) as a shell with a polycarbonate
(PC)/acrylonitrile-butadiene-styrene (ABS) blend core can be printed
using standard fused filament fabrication methods with adequate to
good dimensional accuracy, improved impact resistance, and enhanced
elongation at break relative to samples printed with PC/ABS alone.
The combination of lower crystallinity (28%) of LDPE in comparison
to HDPE (62%) and lower crystallization temperature of LDPE (89 °C)
than HDPE (117 °C) leads to improved dimensional accuracy of
the printed part. However, the elastic modulus of the composite containing
LDPE is only 48% of the part printed with only PC/ABS for flat (
XY
) orientations, whereas the reduction
in modulus with the HDPE shell is significantly less. The mechanical
behavior can be rationalized in terms of aligned fiber composite theory
where anisotropic modulus is expected to be dependent on the angle
between stretching direction and fiber axis. The low cost of LDPE
and HDPE along with the ability to increase impact strength and extensibility
of printed parts further demonstrate the promise of composite core–shell
filaments for additive manufacturing.
Polyelectrolyte charge density, polyelectrolyte-to-surfactant ratio, and micelle species impact the coacervation of the weak polyelectrolyte branched polyethylenimine and oppositely charged micelles composed of SDS and/or poly(ethylene glycol) 4-nonylphenyl 3-sulfopropyl ether potassium salt (PENS).
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