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Enhancing the Oxygen-Barrier Properties of Polylactide by Tailoring the Arrangement of Crystalline Lamellae
journal contribution
posted on 2018-03-27, 00:00 authored by Chunhai Li, Ting Jiang, Jianfeng Wang, Shuangjuan Peng, Hong Wu, Jiabin Shen, Shaoyun Guo, Xi Zhang, Eileen Harkin-JonesThe
gas-barrier properties of semicrystalline polymers can be significantly
adjusted by tailoring the arrangement of their impermeable crystalline
lamellae. In particular, the highest barrier efficiency is achieved
when the arrangement of the lamellae stacks is perpendicular to the
direction of gas diffusion. The work reported on in this paper provides
a strategy to achieve such a lamellar arrangement with the aid of
a self-assembly nucleator and a two-dimensional (2D) interface. PT
(PLA + TMC-300) and PTG (PLA + TMC-300 + graphene) were coextruded
to form alternating PT/PTG multilayers with different layer numbers.
During isothermal treatment at 140 °C, the dissolved TMC-300
first self-assembles into solid-state fibrils that are perpendicular
to the 2D PT/PTG-layered interface due to the induced effects of the
graphene. Subsequently, these TMC-300 fibrils induce the epitaxial
growth of PLA lamellae with a normal parallel to the fibrillar direction
of the TMC-300. In this way, a designed arrangement where the PLA
lamellae stack perpendicular to the direction of gas diffusion is
achieved. As expected, the resulting PLA exhibits impressively enhanced
gas-barrier properties: a decrease of 85.4% in the oxygen permeability
coefficient (PO2) was observed
for the 16-layer sample (0.7 × 10–19 (m3·m)/(m2·s·Pa)) compared with the
sample without layer structure. Through the construction of “lamellae-barrier
walls” by tailoring the arrangement of the lamellae, this work
provides a route to fabricate semicrystalline polymers with superior
gas-barrier properties with great potential for use in high-barrier
applications such as food packing, beverage bottles and fuel tanks.