Screening and Design of the rPET Nucleating Agents Based on Organic Carboxylate Disodium Salt: Crystallization and Mechanical Properties

ABSTRACT Focused on physically recycled poly(ethylene terephthalate) (rPET), the study sought to address the issues of crystallization and mechanical property degradation occurring in the mechanical recycling process by adding organic nucleating agents. The rPET/nucleating agent blends were prepared by the melt blending method, and the microstructure, crystal structure, crystallization, and mechanical properties of the nucleating agents and the blends were systematically studied. The results showed that the organic nucleating agent could react with rPET to form a new substance with ionic end groups. The differences in morphology of nucleating agents significantly affected the nucleation and crystal growth of rPET, and that lattice matching was the key mechanism to control the crystallization behavior. The nucleating agent matched with the rPET lattice could effectively induce the ordered arrangement of rPET molecular chains, significantly reduced the molecular chain rearrangement barrier and interfacial free energy, and then accelerated the nucleation rate. Compared with pure rPET, the flexural strength and notched impact strength of the rPET/nucleating agent blends increased by a maximum of 12.3% and 23.4%, respectively. The study broadened the applications of rPET in recycling by improving its material properties and provided a more practical material solution for the efficient promotion of the plastic recycling economy.