Production and Characterization of Polyvinyl Alcohol-Chitosan-Carrageenan Biocomposite Films Containing St. John's Wort (Hypericum perforatum) Oil

Abstract

This study aims to develop chitosan/poly(vinyl alcohol)/carrageenan biocomposite films incorporating Hypericum perforatum (St. John’s wort) oil (0.1–5%, w/w) and to evaluate the influence of oil incorporation on their structural, mechanical, and dielectric properties. FTIR analysis confirmed strong hydrogen bonding among polymer components and successful oil incorporation without new chemical bond formation. SEM results indicated increased surface heterogeneity and phase separation at higher oil contents. Increasing oil concentration reduced tensile strength (47.1–29.7 MPa), Shore A hardness, density, and dielectric constant (from 4.67 to 3.96), while significantly enhancing tensile strain (30.8–65.7%), demonstrating a plasticizing effect. Overall, it demonstrated that St. John's wort oil can be used as a natural plasticizer in bio-based polymer film applications.