In Situ Synthesized
Self-Reinforced HDPE/UHMWPE Composites
with High Content of Less Entangled UHMWPE and High Gradient-Distributed
Oriented Structures
posted on 2022-12-28, 14:07authored byYuming Chen, Wei Li, Letian Zhang, Chunlin Ye, Gan Tao, Congjing Ren, Binbo Jiang, Jingdai Wang, Yongrong Yang
In this study, tailored polyethylene reactor blends with
the in
situ embedding of a weakly entangled ultra-high-molecular-weight polyethylene
(UHMWPE) were synthesized by the polyhedral oligomeric silsesquioxane
modified Ziegler–Natta (ZN) catalysts using a two-stage cascade
polymerization technique. Holistic improvement of strength/stiffness/toughness
was realized by the common injection modeling owing to the enhanced
formation of an orientated structure which was verified by the patterns
of two-dimensional (2D) small-angle X-ray scattering and 2D wide-angle
X-ray diffraction, as well as the fracture morphology. 30 wt % of
the less entangled UHMWPE was successfully incorporated into the high-density
polyethylene (HDPE) matrix to achieve a synchronously increased tensile
strength (52.4 MPa, +97.7%), Young’s modulus (604.2 MPa, +43.6%),
and impact resistance (74.4 kJ/m2, +675%), compared with
those of the benchmarked HDPE. However, dissipation of a shish-kebab
structure was pronounced in the depth direction of the HDPE spline
reinforced with the disentangled UHMWPE. This dissipation was proved
to partially sacrifice the strength and stiffness. Importantly, the
impact strength is greatly enhanced (+140%) due to the cocrystallization
effect of the disentangled linear UHMWPE chains with the HDPE matrix.
The HDPE matrix reinforced with the weakly entangled UHMWPE presents
wider gradient distribution and orientation degree distribution of
oriented structures (including shish-kebab and stacked lamella) along
the depth direction. Thus, the balance of strength/stiffness/toughness
was synergistically improved with the wider gradient distribution
of oriented structures. This in situ polymerization method with the
weakly entangled UHMWPE offers a promising routine for achieving the
high-performance polyethylene commodity.