Effects of Compressed CO₂ and Cotton Fibers on the Crystallization and Foaming Behaviors of Polylactide

Abstract

The foaming behavior and thermal properties of neat polylactide (PLA) and PLA/cotton-fiber composite foams were investigated in this study. CO2 saturation pressure, temperature, and fibers content significantly affected PLA’s crystallinity and foaming behaviors. At the same saturation temperature (140 °C), a low CO2 pressure generated nonuniform foam and a large unfoamed area due to too high crystallinity with a close-packed structure. At an intermediate pressure, a fine-cell structure was developed due to the presence of numerous less closely packed crystals served as cell nucleating agents. A high CO2 pressure also led to a uniform cell structure but with larger cell sizes due to cell deterioration. Similar to the effect of saturation pressure, an intermediate temperature generated the uniform fine-cell structures. The PLA’s cell morphology was improved by the addition of cotton fibers at a low content because of the increased local stresses through the fibers and transcrystals surrounding the fibers.

Kenaf Composites for Automotive Components: Enhancement in Machinability and Moldability

“…Kenaf/PP/PLA composites prepared at 150 °C showed a lower tensile strength with 200 MPa due to significant yield behaviour, which demonstrated a ductile fracture [32]. These are confirmed by the previous studies, which reported that the PLA materials are brittle because they consist of amorphous phases when the temperature rises between 140 °C to 180 °C [32,33]. For epoxy composites, the tensile strength decreased as the kenaf fibres loading increased, predominantly because of the poor matrix adhesion and unbonding between the matrix and fibres [34].…”

Fabrication of fibrillated and interconnected porous poly(ε-caprolactone) vascular tissue engineering scaffolds by microcellular foaming and polymer leaching

“…Gas foaming is attracting more and more interest from researchers because of its advantages of being free of organic solvents and eco-friendly. 13,14 During this process, carbon dioxide (CO 2 ), which is as widely used as it is inexpensive, non-toxic, highly dissolvable in polymers, recoverable, and reusable, is rst dissolved into a polymer melt at a certain temperature and pressure. Aer the CO 2 turns to a supercritical uid (SCF), it is depressurised to ambient levels to trigger the nucleation.…”

Evaluation of the Zero Shear Viscosity, the D-Content and Processing Conditions as Foam Relevant Parameters for Autoclave Foaming of Standard Polylactide (PLA)

“…Additionally, as these grades are commercialized, they are most probably additivated with nucleating agents by the manufacturer. Also other studies have only revealed a moderate density reduction for batch foamed PLA injection molding grades [35,36]. during the stretching, while the expansion (so called strain induced crystallization) [20].…”