Cold Crystallization of Glassy Polylactide during Solvent Crazing

Abstract

Uniaxial tension accompanied by the orientation and crystallization of polymer chains is one of the powerful methods for the improvement of mechanical properties. Crystallization of amorphous isotropic polylactide (PLA) at room temperature is studied for the first time during the drawing of films in the presence of liquid adsorption-active media (ethanol, water-ethanol mixtures, and n-heptane) by the solvent crazing mechanism. The crystalline structure arises only under simultaneous actions of a liquid medium and a tensile stress and does not depend on the nature of the environment. The degree of polymer crystallinity increases nearly linearly with the growth in the fraction of the fibrillar material and reaches a maximum value of 42-45%. It has been stated that polymer crystallization happens in crazes involving nanofibrils with a diameter of about 10-20 nm without affecting the bulk polymer parts. Wide-angle X-ray scattering has been used to confirm that the crazing-induced crystallization is accompanied by the formation of the α'-crystalline phase with crystallite sizes (X-ray coherent scattering region) of 3-5 nm, depending on the nature of the liquid medium. After stretching in liquid media to a high tensile strain, the strength of a PLA film has increased to 200 MPa.

Degradation of Structurally Modified Polylactide under the Controlled Composting of Food Waste

“…In this case, the development of large deformations occurs according to the crazing mechanism through the formation of a highly dispersed fibrillar-porous structure with its subsequent collapse. As previously shown in [41,42], orientation of the polymer film is followed by "cold" crystallization. The samples were dried under isometric conditions to constant weight after stretching.…”

Development of Biodegradable Polyamide 4/Polyvinyl Alcohol/Poly(lactic acid) Multilayer Films with Tunable Water Barrier Property and Superior Oxygen Barrier Property

“…Water molecules in the PA4 film act as plasticizers, enabling the polymer chains to fully extend . However, PLA undergoes brittle fracture during stretching due to the formation of nucleation centers in cracks and rapid physical aging . The combination of PA4 and PLA resulted in good interfacial interaction between the layers, mediated by PVA, which made PA4 the main load-bearing phase during tensile test.…”

“…8 However, PLA undergoes brittle fracture during stretching due to the formation of nucleation centers in cracks and rapid physical aging. 37 The combination of PA4 and PLA resulted in good interfacial interaction between the layers, mediated by PVA, which made PA4 the main load-bearing phase during tensile test. With an increase in PLA content in the multilayer Table 3 film, PLA was prone to sliding under load and became the starting point for fracture, leading to a decrease in TS and EB.…”

High-Throughput Small-Molecule Crystallography at the ‘Belok’ Beamline of the Kurchatov Synchrotron Radiation Source: Transition Metal Complexes with Azomethine Ligands as a Case Study

“…For X-ray scattering experiments on partly crystalline materials, we try to fully exploit the 2D nature of X-ray images to get insight into changes of preferred orientation and crystallinity of polymers, liquid crystals, etc. [50,51].…”