PLA Foaming Process and Its Research Progress

Abstract

Poly(lactic acid) (PLA) foams offer low density, high specific strength, biocompatibility, and biodegradability, and are therefore regarded as promising sustainable alternatives to conventional petroleum-based foams. Their broader application, however, is constrained by the inherently low melt strength, slow crystallization kinetics, and narrow processing window of PLA, which make it difficult to achieve high expansion ratios together with uniform and stable cellular structures. This review summarizes the principles, equipment, and application ranges of extrusion foaming, autoclave foaming, injection foaming, and foaming integrated with 3D printing. Physical, chemical, and combined foaming mechanisms are discussed, with particular emphasis on how material characteristics and processing conditions govern cell nucleation, growth, and stabilization. Recent developments in foaming technologies and processing equipment are reviewed, together with the remaining challenges in cellular uniformity, process reliability, manufacturing cost, and scale-up. Emerging research directions include intelligent process control, sustainable blowing agents, precise tailoring of cellular architectures, and multifunctional PLA foams. These advances are expected to support the performance enhancement and industrial adoption of PLA foam products.