Morphology and thermal properties of poly(l-lactic acid) nucleated with 2,2′-(butane-1,4-diylbis(oxy))di(benzohydrazide)†

Abstract

This study evaluates the modification of biodegradable poly(L-lactide) (PLLA) using a novel organic nucleating agent, 2,2′-(butane-1,4-diylbis(oxy))di(benzohydrazide) (BDOBH) with a low concentration range from (0.3–3 wt%). The novelty of this work lies in the development and application of BDOBH as a highly efficient, low-loading organic nucleator tailored to improve PLLA's crystallization behavior and thermal properties—key limitations in its broader industrial use. The evaluation is conducted through differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), and polarized optical microscopy. FTIR analysis reveals the presence of H-bonding interaction between BDOBH and PLLA. DSC results significantly improve PLLA's crystallization rate, with BDOBH in a concentration range from 0.3 to 0.7 wt%. The total crystallinity of PLLA increases from 12% to 56–60% without a change in PLA's crystallography; moreover, the maximum temperature of the cold crystallization peak shifts to a lower value by 35 °C after incorporating BDOBH-0.7 into PLLA. POM results reveal a drastic decrease in the spherulitic size of PLLA. Furthermore, the presence of BDOBH enhances the thermal stability of PLLA. The nonisothermal cold crystallization behavior of PLLA nucleated by BDOBH is evaluated using the modified Avrami and Mo models. Multiple indicators of nonisothermal crystallization, including the crystallization half-time and crystallization rate constant, indicate that BDOBH greatly expedites the crystallization process. The activation energy values of the plain PLLA and PLLA-BDOBH, as computed using the Kissinger–Akahira–Sunose (KAS) model, decrease when BDOBH is incorporated. These findings highlight BDOBH's potential as a cost-effective and scalable additive to tailor PLLA crystallization, supporting its use in environmentally friendly packaging, biomedical devices, and other high-performance biodegradable applications.