Enhanced Foaming Properties of Polylactic Acid (PLA) via In-situ Fibrillation with Polyethylene Furanoate (PEF) Nanofibers

Polylactic acid (PLA) is a promising biodegradable and biocompatible polymer with renewable raw materials and ease of processing [1, 2]. Its foam material, known for its lightweight, thermal insulation, sound absorption, and high specific strength, finds widespread applications in food packaging, transportation, and aerospace [3]. However, PLA's slow crystallization rate, low melt strength, and poor heat resistance pose challenges in achieving high expansion ratio foaming samples, limiting its wider use. This study focuses on enhancing the crystallinity and melt strength of PLA to improve its foaming performance by employing in-situ fibrillation technology. In-situ fibrillation is a composite modification technique that uniformly disperses nanofibers within the polymer matrix, promoting heterogeneous nucleation and improving melt strength. In this study, polyethylene furanoate (PEF), a plant-based polymer, was chosen as the dispersed phase. PLA/PEF composite materials containing varying amounts of PEF nanofibers were prepared via twin-screw extrusion and spinning. The impact of different PEF nanofiber contents on PLA's basic properties and foaming behavior was investigated. Our key findings reveal that PEF nanofibers form a physically entangled network within the PLA matrix, significantly increasing PLA's melt strength. This network also promotes heterogeneous nucleation, leading to a notable increase in PLA's crystallization rate and degree. The addition of 3 wt% PEF nanofibers resulted in a 50% increase in PLA's crystallinity and an elevation of the Vicat softening temperature from 62 °C to 157 °C. These findings demonstrate the potential of in-situ fibrillation with PEF nanofibers for effectively enhancing PLA's foaming performance, opening possibilities for broader applications in various industries.