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ScCO2-assisted fabrication and compressive property of poly (lactic acid) foam reinforced by in-situ polytetrafluoroethylene fibrils
Summary
Researchers developed biodegradable poly(lactic acid) foam reinforced with polytetrafluoroethylene fibrils using supercritical CO2 foaming, achieving a 30% improvement in specific compressive strength and two orders of magnitude increase in storage modulus at 5 wt% PTFE content. The approach improves PLA's typically poor melt strength and slow crystallization, making it a more viable bio-based alternative to petroleum-based plastic foams.
As an effective alternative for petrochemical-based polymers, bio-based poly (lactic acid) (PLA) foam has been anticipated to alleviate enormous environmental pollution caused by microplastics. However, some difficulties involved in PLA foaming process due to the inherently poor melt strength and crystallization properties. In this context, a small amount of polytetrafluoroethylene (PTFE) was incorporated into PLA matrix to solve the aforementioned issues. Scanning electron microscopy measurement exhibited that PTFE fibrils and their physical networks were formed in molten PLA after blending. Due to these PTFE networks, approximately 2 orders of magnitudes increment in the storage modulus and more than 20% improvement in crystallinity of PLA were obtained. Diverse PLA samples were successfully foamed by a cost-effective, green and supercritical CO-assisted foaming method. The PLA/PTFE foam with the PTFE content of 5 wt% (PLA/PTFE5) possessed the smallest pore size (9.51 μm) and the highest pore density (2.60 × 10 pores/cm). In addition, the average specific compressive strength of PLA/PTFE5 foam was enhanced 30% in comparison with that of pure PLA foam. Overall, this study could provide a prospective strategy for developing bioderived and biodegradable polymer foams with controllable pore structures and high compression property.