Preparation of PEAT/Lignin Composites with Excellent Mechanical Properties and UV Aging Resistance via the Sustainable Utilization of Lignin

Abstract

To address the issue of lignin agglomeration in poly(ethylene adipate-co-terephthalate) (PEAT) matrix, which leads to degraded composite performance, this study employed vinyltrimethoxysilane (VTMS) to modify lignin, producing VTMS-grafted lignin (VL). Subsequently, VL was blended with PEAT at different proportions to fabricate PEAT/VL composites. The mechanical properties, micromorphology, thermal behavior, water absorption, and UV-shielding performance of the resulting composite films were systematically evaluated to determine the effect of VL content on the properties of PEAT/VL composites. The results indicate that VTMS graft modification significantly improved the dispersion of lignin in the PEAT matrix and enhanced the interfacial compatibility between the two phases. SEM and contact angle measurements confirmed that through simple silane modification, the contact angle of lignin increased from 53.1° to 130.2°, significantly enhancing its hydrophobicity and effectively suppressing the agglomeration of lignin particles in the PEAT matrix. Compared with the unmodified lignin (AL) system, the tensile strength of the PEAT/VL-5% composite increased from 23.4 to 28.9 MPa (a 23.5% increase), and the elongation at break increased from 990% to 1172% (an 18.4% increase). When the VL content was 10%, the tensile strength and elongation at break of the PEAT/VL composite were comparable to those of pure PEAT and could still meet the practical application requirements for films. At the same time, the PEAT/VL composites exhibit highly efficient full-spectrum UV shielding performance in the 280 nm-400 nm UV range. Furthermore, after 144 h of UV aging, the tensile strength retention and elongation at break retention of the PEAT/VL-5% and PEAT/VL-10% composites exceeded 57% and 88%, respectively, effectively delaying the photodegradation of PEAT. This study provides a valuable reference for the development of PEAT-based biodegradable composites with both excellent mechanical properties and UV-shielding capabilities, laying the foundation for their large-scale application in environmentally friendly fields such as packaging and agricultural mulch films.