Lamellae orientation and structure evolution of reinforced poly(lactic acid) via equal channel angular extrusion

Abstract

The aim of this study was to improve the mechanical performance of biodegradable poly(L‐lactic acid) through equal channel angular extrusion (ECAE). Changes in morphology induced by the ECAE shear deformation in poly(lactic acid) (PLA) were investigated. Differential scanning calorimeter results suggested a significant improvement in crystallinity of ECAE‐deformed PLA depending on its thermal condition and deformation force. Two‐dimensional wide angle X‐ray diffraction measurement and polarized FTIR spectroscopies of ECAE‐deformed PLA revealed a structural network in the crystalline region, and the taut tie molecules (TTMs) connecting lamellae also stretched. Scanning electron microscope results showed that the macro‐fibrils were generated, and the oriented structures were arranged along the nominal shear direction at a certain angle. Both the inclined macro‐fibrils structure and the oriented TTMs within fibrils were beneficial in improving mechanical performance. Finally, the mechanical property tests showed that the mechanical properties of PLA were improved overall. The tensile strength, elongation, impact strength, and bending strength increased by 28%, 123.8%, 224.3%, and 47.6%, respectively. Meantime, a transition from brittle fracture to ductile fracture was observed from the original PLA billet to ECAE‐deformed one. Therefore, the ECAE process represents a promising approach for comprehensively reinforced PLA.

Robust Osteoconductive β-Tricalcium Phosphate/L-poly(lactic acid) Membrane via Orientation-Strengthening Technology

“…Stretching or extruding semicrystalline materials at a certain temperature to obtain an oriented structure is a common method in additive manufacturing to enhance the mechanical strength of materials. , As a material for bone repair, PLLA lacks osteogenic activity. β-TCP is frequently added to organic materials as inorganic particles to increase the osteogenesis.…”