Evaluation of Mechanical and Interfacial Properties of Bio-Composites Based on Poly(Lactic Acid) with Natural Cellulose Fibers

TLDR

The growing circular economy and demand for sustainable materials are expanding the bio‑composite market, with natural fibers in biodegradable polymer matrices—especially PLA—offering a promising alternative to fossil‑based composites. This study aims to couple PLA with natural cellulose fibers to reduce costs, enhance degradability, and enable tuning of bio‑composite properties for packaging and agricultural applications. The authors fabricated PLA composites reinforced with two types of cellulose fibers at 5–20 wt % and assessed tensile and impact strength while using analytical models to estimate fiber–matrix adhesion and predict stiffness.

Abstract

The circular economy policy and the interest for sustainable material are inducing a constant expansion of the bio-composites market. The opportunity of using natural fibers in bio-based and biodegradable polymeric matrices, derived from industrial and/or agricultural waste, represents a stimulating challenge in the replacement of traditional composites based on fossil sources. The coupling of bioplastics with natural fibers in order to lower costs and promote degradability is one of the primary objectives of research, above all in the packaging and agricultural sectors where large amounts of non-recyclable plastics are generated, inducing a serious problem for plastic disposal and potential accumulation in the environment. Among biopolymers, poly(lactic acid) (PLA) is one of the most used compostable, bio-based polymeric matrices, since it exhibits process ability and mechanical properties compatible with a wide range of applications. In this study, two types of cellulosic fibers were processed with PLA in order to obtain bio-composites with different percentages of microfibers (5%, 10%, 20%). The mechanical properties were evaluated (tensile and impact test), and analytical models were applied in order to estimate the adhesion between matrix and fibers and to predict the material’s stiffness. Understanding these properties is of particular importance in order to be able to tune and project the final characteristics of bio-composites.