Preparation of Sunflower Straw Cellulose Nanofibers/ Poly(lactic acid)/ Poly(butylene adipate-co-terephthalate) Composites by Co-precipitation and Hot-pressing

Abstract

Polylactic acid (PLA) is a rigid biopolymer, while poly(butylene adipate-co-terephthalate) (PBAT) is a flexible biodegradable polymer. To comprehensively enhance the mechanical properties of PLA/PBAT composites, sunflower straw cellulose nanofibers (SSCNFs) were isolated from sunflower straw (SS) via TEMPO oxidation treatments and used as reinforcement. Using a PLA/PBAT blend (60:40 by mass) as the matrix, SSCNFs-reinforced PLA/PBAT composites were prepared using a co-precipitation and hot-pressing method. The morphology and structure of the SSCNFs were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and nanoparticle size and zeta potential analysis. The mechanical and thermal properties of the composites were tested. The tensile and flexural properties of the composites were improved with increasing SSCNFs content. When the SSCNF content was 16 wt%, the composites reached a tensile strength of 20.06 ± 0.61 MPa (an 11.69% enhancement), a tensile modulus of 732.57 ± 42.72 MPa (a 56.64% enhancement), a flexural strength of 31.76 ± 0.54 MPa (a 20.21% enhancement), and a flexural modulus of 2030.42 ± 36.37 MPa (a 77.50% enhancement). Although thermal stability and water absorption were slightly decreased, UV shielding capacity and hydrophobicity were enhanced. The prepared composites exhibited well-balanced overall performance and potential for replacing traditional commercial polymers.