Largely enhanced mechanical performance of poly(butylene succinate) multiple system via shear stress-induced orientation of the hierarchical structure

Abstract

In order to fabricate an oriented hierarchical structure of biodegradable poly(butylene succinate) (PBS) and thus improve its mechanical properties, oscillation shear stress was imposed on the melt during solidification, aiming to stretch the polymer chains and suppress the relaxation of the oriented chains. Abundant oriented interlocked shish-kebabs were formed with the aid of intense shear stress and poly(L-lactide) (PLA), which was demonstrated through small-angle X-ray scattering (SAXS), scanning electronic microscopy, and wide-angle X-ray diffraction (WAXD). The distinctly oriented structure in the core layer of the structured samples could well clarify the role of PLA in promoting a shear-induced oriented hierarchical structure of PBS. With such unique hierarchical structure, the tensile strength, modulus and impact strength of the structured sample with 10 wt% PLA were simultaneously enhanced from 36.4 MPa, 390.2 MPa and 23.3 kJ m⁻² for conventional neat PBS to 49.1 MPa, 634.0 MPa and 28.7 kJ m⁻², showing a remarkable enhancement of 34.9%, 62.5% and 23.2%, respectively. The simultaneous reinforcement and toughening was achieved due to the formation of the oriented hierarchical structure including oriented chain segments, lamellae and fibrous crystals. Cavities form along with lamellae fragmentation and recrystallization during tensile deforming, as revealed by WAXD and SAXS of tensile broken samples. Compared with the isotropic structure, the oriented hierarchical structure not only prevents the slippage of molecular chains and bears larger stress, but also limits the formation of cavities due to the high density. These surprising results are of importance to bridge the gap between the nature of the hierarchical structure and performance of PBS, offering helpful guidance to design and fabricate the structure of PBS during practical processing.