Preparation of lignin-based nucleating agents and their effects on the crystallization behavior and properties of poly(ethylene terephthalate) esters

Abstract

This study focuses on the optimization of crystalline properties and tensile strength of poly(ethylene terephthalate) (PET) through the use of lignin as a nucleating agent and its carboxylation modification. Lignin, as a unique amorphous and aromatic-rich macromolecule, can play a key role in heterophase nucleation during the nucleation process. After carboxylation modification, lignin provides more chemical nucleation sites for PET crystallization, which are driven by the ion-cluster-induced nucleation mechanism. In order to explore this modification effect in depth, PET composites with different carboxymethylated lignin contents were prepared and subjected to various characterization analyses, including infrared spectral analysis, electron microscope observation, differential scanning calorimetry test, thermogravimetric analysis, and tensile strength test. The experimental data showed that the composites containing carboxymethylated lignin showed a significant increase in crystallinity and crystallization rate compared to pure PET. Specifically, its crystallinity increased significantly from 20.3 % to 27.7 %, and the crystallization temperature was also significantly increased from the original 199 °C–214 °C. This enhancement not only optimized the microstructure of the material, but also directly reflected in the enhancement of tensile strength, i.e., from 33.9 MPa to 53.1 MPa. These findings not only provide new ideas for the performance enhancement of PET materials, but also demonstrate the great potential of lignin, a biomaterial resource, in the modification of polymer materials.