Properties and mechanism of amino acid esterification-modified laser-printed waste paper fibers/carbon fiber-reinforced PVA-based flexible conductive composite films

Abstract

Laser-printed waste paper fiber (WF), a high-quality secondary fiber, has gained attention for its potential in high-value recycling. In this study, we employed polyvinyl alcohol as the matrix polymer and systematically investigated three amino acid esterification agents (L-glutamic acid, lysine, and alanine) for WF surface modification. Additionally, high-performance carbon fiber (CF) was incorporated as the reinforcement material for flexible conductive film applications. The objective of this research was to investigate the mechanism behind the amino acid esterification modification of WF, as well as the enhancement effects of both amino acid-modified WF and CF incorporation on flexible conductive films. Infrared spectroscopy and X-ray diffraction analyses revealed that the amino acid esterification reaction did not alter the crystalline structure of cellulose; rather, it predominantly occurred on the surface of WF. Among the amino acids studied, the grafting rate of L-alanine on the surface of WF was the highest. The film prepared using 1.0 g of L-alanine-modified WF exhibited the maximum tensile strength, measuring 51.80 MPa. Furthermore, CF addition enhanced the tensile strength by 52.4% and established a conductive network, achieving a conductivity of 0.46 S/cm. This study demonstrates the feasibility of creating flexible conductive films from a combination of WF and CF, providing insights for promoting the high-value utilization of waste paper fibers and developing novel flexible conductive films.