Effect of amide-modified attapulgite on the crystallization and supercritical CO2 foaming behavior of poly(lactic acid).

In this work, amidation-modified ATP (A-ATP) was prepared with attapulgite (ATP) through acid washing activation, silane coupling, and amidation reactions. Then, A-ATP was characterization by FTIR, contact angle measurements, XPS, XRD, and TGA, which confirmed the removal of carbonate impurities, successful introduction of hydrophobic groups (contact angle increased from 7° to 70°), and maintenance of stable crystalline structure in A-ATP. Furthermore, polylactic acid (PLA)/A-ATP nanocomposite foams were fabricated via supercritical CO2 autoclave foaming technology with PLA as the matrix and A-ATP as the filler. It was demonstrated that 0.6 wt% A-ATP significantly optimized the foam structure (smallest average cell size with reduced standard deviation) and enhanced compressive properties. Specifically, the compressive strength of PLA/A-ATP nanocomposite foams reached 116.61 kPa, and its specific compressive modulus was 5639 kPa/(g·cm-3), representing 99 % and 142 % improvements over PLA, respectively. DSC and rheological behavior indicated that A-ATP reduced PLA's cold crystallization temperature, increased crystallinity up to 17.94 %, and improved melt fluidity. Molecular dynamics simulations further revealed that 0.6 wt% A-ATP promoted CO2 diffusion in PLA, elevated the diffusion coefficient from 2.711 × 10-6 to 4.190 × 10-6 cm2/s. This study provides a novel strategy for enhancing the performance of PLA foams.