In Situ Formation of Microfibrillar Crystalline Superstructure: Achieving High-Performance Polylactide

Abstract

As a biobased and biodegradable polyester, polylactide (PLA) is widely applied in disposable products, biomedical devices, and textiles. Nevertheless, due to its inherent brittleness and inferior strength, simultaneously reinforcing and toughening of PLA without sacrificing its biodegradability is highly desirable. In this work, a robust assembly consisting of compact and well-ordered microfibrillar crystalline superstructure (FCS) surrounded by slightly oriented amorphism, is achieved by a combined external force field. Unlike the classic crystalline superstructures such as shish-kebabs, cylindrites, and lamellae, the newfound FCS with diameter of about 100 nm and length of several tens of micrometers is aggregated with well-aligned crystalline nanofibers. FCS can serve as discontinuous fiber to self-reinforce the amorphous PLA; more importantly, FCS can also act as rivets to pin the propagating fibrillar crazes leading to the formation of dense fibrillar crazes during stretching, which dissipates much energy and translates the failure of PLA from brittle to ductile. Consequently, PLA with FCS exhibits exceptionally simultaneous enhancement in ductility, strength, and stiffness, outperforming normal PLA with increments of 728, 55, and 70% in elongation at break, strength, and modulus, respectively. Therefore, FSC exhibits competitive advantages in achieving high-performance PLA even for other semicrystalline polymers. More significantly, this newfound crystalline superstructure (FCS) provides a new structural model to establish the correlation between structure and performance.

Correlation between fibril structures and mechanical properties of polyacrylonitrile fibers during the dry‐jet wet spinning process

“…On the one hand, the microfibrils movement and slippage during the spinning process resulted in pore collapsed, which was contributed to decrease the content of the pore defects and surface defects. Therefore, it might reduce the probability of the stress accumulation and crack formation under load; on the other hand, served as the self‐reinforcement in PAN fibers, closely interlinked fibrils could efficiently resist the cracks propagation and dissipate the much energy . Consequently, the PAN precursor fibers with the homogeneous, compact, well‐oriented, and closely interlinked fibrils, presented high tensile strength and initial modulus.…”

“…Wang et al 23,24 combined the ultrasonic breakup and solvent etching to separate the fibril elements from PAN fibers and proposed the formation process of the periodic lamellae structures in microfibrils. Li et al 25 suggested that the fibrils served as the self-reinforcing elements to enhance the material mechanical properties.…”

Effective Control of Laser‐Induced Carbonization Using Low‐Density Polyethylene/Polystyrene Multilayered Structure via Nanolayer Coextrusion

“…[23][24][25][26] This technology can forcibly assemble one or more polymers into a film with a multilayered structure, where the thickness and number of layers can be effectively regulated by related parameters such as the multiplying elements, extrusion rate, and stretch rate. [27][28][29] Each layer is constructed in a unique 2D confined space. [30,31] By changing the size of this 2D confined space, a multilayered film will exhibit improved compatibility, conductive and thermal barriers, and rheological and mechanical properties.…”

“…Nanolayer coextrusion is a novel technology that can produce a polymer film with a special multilayered structure . This technology can forcibly assemble one or more polymers into a film with a multilayered structure, where the thickness and number of layers can be effectively regulated by related parameters such as the multiplying elements, extrusion rate, and stretch rate . Each layer is constructed in a unique 2D confined space .…”

Three‐dimensional isothermal simulation of PP melt flow in laminating‐multiplying elements based on the finite element method

“…However, the high aspect ratio would supply a stronger shear stress. Stronger shear stress leaded to a stronger shear‐induced orientation of polymer chains and fillers in polymer composites , which had unique advantages in the field of the crystallization behavior of polymer chains and the dispersion and orientation of fillers , but might worsen the interface deformations. For example, we designed a rectangle LME with a higher aspect ratio of 20:1 at the outlet, the schematic of which is shown in Fig.…”